Open IT

Setting root password in Ubuntu

2012-01-06T17:13:00.001-05:00

Its quite simple:

- Open a terminal
- sudo passwd root

& follow the instructions.

More on Swapping Vs. Paging

2010-03-03T15:41:00.000-05:00

Just using a lot of swap space doesn’t necessarily mean that you need more memory. Here’s how to tell when Linux is happy with the available memory and when it needs more.

Linux novices often find virtual memory mysterious, but with a grasp of the fundamental concepts, it’s easy to understand. With this knowledge, you can monitor your system’s memory utilization using vmstat and detect problems that can adversely affect system performance.
How Virtual Memory Works

Physical memory-the actual RAM installed-is a finite resource on any system. The Linux memory handler manages the allocation of that limited resource by freeing portions of physical memory when possible.

All processes use memory, of course, but each process doesn’t need all its allocated memory all the time. Taking advantage of this fact, the kernel frees up physical memory by writing some or all of a process’ memory to disk until it’s needed again.

The kernel uses paging and swapping to perform this memory management. Paging refers to writing portions, termed pages, of a process’ memory to disk. Swapping, strictly speaking, refers to writing the entire process, not just part, to disk. In Linux, true swapping is exceedingly rare, but the terms paging and swapping often are used interchangeably.

When pages are written to disk, the event is called a page-out, and when pages are returned to physical memory, the event is called a page-in. A page fault occurs when the kernel needs a page, finds it doesn’t exist in physical memory because it has been paged-out, and re-reads it in from disk.

Page-ins are common, normal and are not a cause for concern. For example, when an application first starts up, its executable image and data are paged-in. This is normal behavior.

Page-outs, however, can be a sign of trouble. When the kernel detects that memory is running low, it attempts to free up memory by paging out. Though this may happen briefly from time to time, if page-outs are plentiful and constant, the kernel can reach a point where it’s actually spending more time managing paging activity than running the applications, and system performance suffers. This woeful state is referred to as thrashing.

Using swap space is not inherently bad. Rather, it’s intense paging activity that’s problematic. For instance, if your most-memory-intensive application is idle, it’s fine for portions of it to be set aside when another large job is active. Memory pages belonging to an idle application are better set aside so the kernel can use physical memory for disk buffering.
Using vmstat

vmstat, as its name suggests, reports virtual memory statistics. It shows how much virtual memory there is, how much is free and paging activity. Most important, you can observe page-ins and page-outs as they happen. This is extremely useful.

To monitor the virtual memory activity on your system, it’s best to use vmstat with a delay. A delay is the number of seconds between updates. If you don’t supply a delay, vmstat reports the averages since the last boot and quit. Five seconds is the recommended delay interval.

To run vmstat with a five-second delay, type:

vmstat 5

You also can specify a count, which indicates how many updates you want to see before vmstat quits. If you don’t specify a count, the count defaults to infinity, but you can stop output with Ctrl-C.

To run vmstat with ten updates, five seconds apart, type:

vmstat 5 10

Here’s an example of a system free of paging activity:

procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
0 0 0 29232 116972 4524 244900 0 0 0 0 0 0 0 0 0
0 0 0 29232 116972 4524 244900 0 0 0 0 2560 6 0 1 99
0 0 0 29232 116972 4524 244900 0 0 0 0 2574 10 0 2 98

All fields are explained in the vmstat man page, but the most important columns for this article are free, si and so. The free column shows the amount of free memory, si shows page-ins and so shows page-outs. In this example, the so column is zero consistently, indicating there are no page-outs.

The abbreviations so and si are used instead of the more accurate po and pi for historical reasons.

Here’s an example of a system with paging activity:

procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
. . .
1 0 0 13344 1444 1308 19692 0 168 129 42 1505 713 20 11 69
1 0 0 13856 1640 1308 18524 64 516 379 129 4341 646 24 34 42
3 0 0 13856 1084 1308 18316 56 64 14 0 320 1022 84 9 8

Notice the nonzero so values indicating there is not enough physical memory and the kernel is paging out. You can use top and ps to identify the processes that are using the most memory.

You also can use top to show memory and swap statistics. Here is an example of the uppermost portion of a typical top report:

14:23:19 up 348 days, 3:02, 1 user, load average: 0.00, 0.00, 0.00
55 processes: 54 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: 0.0% user, 2.4% system, 0.0% nice, 97.6% idle
Mem: 481076K total, 367508K used, 113568K free, 4712K buffers
Swap: 1004052K total, 29852K used, 974200K free, 244396K cached

For more information about top, see the top man page.
Conclusion

It isn’t necessarily bad for your system to be using some of its swap space. But if you discover your system is often running low on physical memory and paging is causing performance to suffer, add more memory. If you can’t add more memory, run memory-intensive jobs at different times of the day, avoid running nonessential jobs when memory demand is high or distribute jobs across multiple systems if possible.

20 Linux System Monitoring Tools Every SysAdmin Should Know

2010-02-23T23:56:00.000-05:00

http://www.cyberciti.biz/tips/top-linux-monitoring-tools.html

Solaris Swapping and Paging

2010-02-23T16:25:00.001-05:00

http://www.sunmanagers.org/archives/1996/0436.html

Displaying %ENV completely

2010-02-23T12:31:00.002-05:00

#! /usr/bin/perl -w

use strict;

my $keyy;

foreach $keyy (keys %ENV)
{

print "$keyy and its value = $ENV{$keyy} \n";

}

1;

Perl use lib, unshift difference

2010-02-23T12:06:00.006-05:00

What's the difference between use, unshift and PERL5LIB when adding/including module path?

A.

use lib - is a compile time inclusion. Try this example:

#! /usr/bin/perl -w

use strict;

print "@INC\n";
use lib '/home/kdranjan/Perl/Dynamic';
Print "@INC\n";

Run it and it will display: (Both are same because added path was included at compile time)
---------------------------
- /home/kdranjan/Perl/Dynamic /etc/perl /usr/local/lib/perl/5.10.0 /usr/local/share/perl/5.10.0 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_perl .

- /home/kdranjan/Perl/Dynamic /etc/perl /usr/local/lib/perl/5.10.0 /usr/local/share/perl/5.10.0 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_perl .

==========================================================

unshift - is a run time inclusion.

Modify previous script a bit like this:
---------------------------------------
#! /usr/bin/perl -w

use strict;

print "@INC\n";
unshift(@INC, '/home/kdranjan/Perl/Dynamic');
print "@INC\n";

- /etc/perl /usr/local/lib/perl/5.10.0 /usr/local/share/perl/5.10.0 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_perl .

- /home/kdranjan/Perl/Dynamic /etc/perl /usr/local/lib/perl/5.10.0 /usr/local/share/perl/5.10.0 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_perl .

How does gcc, ld and g++ work

2010-02-21T01:33:00.000-05:00

http://www.linuxjournal.com/article/6463

Defunct (Zombie) process, preap and orphan process

2010-02-18T23:19:00.001-05:00

A defunct (or zombie) process is one whose exit status has yet to be reaped by its parent. So when a process shows as "defunct" in ps, you need to reap it. Here's how:

preap(1) - force a defunct process to be reaped by its parent

Syntax: /usr/bin/preap PID

So, to get rid of all zombies on our system, all we have to do is script this to reap all process marked as defunct:

/usr/bin/preap $(ps -ef | grep defunct | awk '{ print $2 }' | xargs)

So, what's an orphan process then? If the parent of a defunct process happens to exit, it becomes an orphan, and is asigned PID 1 as a parent - see init(1M).

Solaris: How to know all the options of a command from process id

2010-02-18T22:45:00.002-05:00

Question: How to find out, What all options or inputs were specified with a unix tool, from process id?

Ans: Solaris supports 'pargs', which, when, run with , will throw all the inputs specified with the command. Question is, why is 'ps -eaf' not sufficient. Answer lies in what 'ps -eaf' prints. 'ps -eaf' can print only limited number of outputs on one line, mostly, 80 char. What if, command + inputs were bigger/wider than 80 chars.

Also, 'pargs -e can also print the environment variable path.

mod_bandwidth in Apache Web Servers

2010-02-10T20:14:00.004-05:00

Q. How can we deal with the situation where we can afford only a limited amount of bandwidth but some of the service's content is large such as streaming media or large files?

A. mod_bandwidth is a Apache module that enables the setting of server-side wide or per-connection bandwidth limits, based on directory, size of files, and remote IP/Domain.

http://www.cohprog.com/mod_bandwidth.html

Apache Load Balancing

2010-02-10T20:08:00.002-05:00

Load balancing can help distribute load off of one Apache Web Server machine to logically and geographically distributed Apache Web Servers.

Load balancing can be achieved using 'mod_backhand', Cisco LocalDirector.

URL for mod_backhand:

http://www.backhand.org/mod_backhand/

User who are really serious about tuning their Web Servers can refer to
'Web Performance Tuning' by Patrick Killelea (O'Reilly).

What is Taint mode in perl

2010-02-09T10:01:00.002-05:00

http://gunther.web66.com/FAQS/taintmode.html

http://perldoc.perl.org/perlsec.html

Single Line Swap in Perl

2010-02-09T09:56:00.002-05:00

($foo, $bar) = ($bar, $foo)

will work just fine.

Perl 5.6 Vs 5.8

2010-02-09T09:39:00.002-05:00

Perl 5.6.1 and Perl 5.8.x are not binary compatible (It means that user will have to download the source code in c and install it using their c development and build environment). Binary versions may be available directly from vendors such as RedHat or Ubuntu etc.

There are a few important differences to consider:
-------------------------------------------------

5.6.1:
- Smaller installation,
- Faster in some cases,
- Broken threading model,
- No unicode

5.8.x:
- Larger installation,
- Threading model mostly works,
- Has unicode support

Highlights In 5.8.0

- Better Unicode Support:
Unicode support has been much enhanced since 5.6, at all levels:
- now supports Unicode 3.2.0 (5.6.1 supports 3.0.1)
- at the language (and internals) level Unicode support is
now more ubiquitous and robust
- regular expressions now work with Unicode
- support for non-Latin encodings (such as the various
Chinese/Japanese/Korean encodings) through the Encode module

- New Threads Implementation:
A new multithreading implementation called interpreter threads,
or "ithreads" for short, is available, their use instead of the
old "5.005 threads" is strongly encouraged. The major difference
is that in ithreads any data sharing must be done explicitly.

- New IO Implementation:
the new PerlIO implementation is both a portable stdio implementation
(at the source code level) and a flexible new framework for richer
I/O behaviours

- Better Numeric Accuracy:
previous Perls relied on vendors' string-to-number and back
routines which in some cases proved to be too much trust
leading to nonportable and wrong behaviours

- 64-bit support:
64-bit support is now considered to be mature -- if your platform
supports 64-bit integers or address space, you can compile Perl to
use those

- Safe Signals:
in previous versions of Perl signals could corrupt Perl's internal state

- Many New Modules:
Digest::MD5, File::Temp, Filter::Simple, libnet, List::Util,
Memoize, MIME::Base64, Scalar::Util, Storable, Switch,
Test::More, Test::Simple, Text::Balanced, Tie::File, ...

- Extensive Regression Testing:
Perl has now almost six times as many tests as in 5.6,
and the code is test built daily on several platforms

Incompatibilities

- BINARY INCOMPATIBLE:
mainly because of the PerlIO introduction, Perl 5.8 is not
binary compatible with any earlier Perl release, XS MODULES
WILL HAVE TO BE RECOMPILED!

- AIX Dynaloading:
Perl uses now AIX dynaloading, instead of the older emulated
version, to be more compatible with other applications on AIX

- 64-bit Platforms No Longer Use Perl Malloc:
the Perl malloc seems to have various problems on platforms
with 64-bit addressing, therefore the default in these cases
is to use the native malloc

- Hashing Order Changed Once Again:
the function used in the implementation of hashes was changed
to a better one once again, but your code shouldn't be expecting
any particular key ordering

- Attributes For my Now Handled At Run-Time:
the attributes for my() are now run-time, as opposed to compile time

- REF(...) instead of SCALAR(...):
to be consistent with ref()'s results, references to references
now stringify as "REF(...)"

- Unicode Model Changed (no more "use utf8", almost)
In Perl 5.6 "Unicodeness" was lexically scoped to the operations;
in Perl 5.8 "Unicodeness" is bound to the data. The only remaining
use of "use utf8" is when the Perl script itself is written in the
UTF-8 encoding of Unicode.

- VMS: Socket Extension Dynamic, IEEE fp Default on Alpha
- the Socket extension is now dynamic rather than static, which may
cause problems in really old VMS installations
- the IEEE floating point is now the default format in OpenVMS Alpha,
see README.vms for reasons and other details

Nomenclature Change

- What the "Camel III" book called an "IO discipline"
is now called an "IO layer"

Deprecations

- dump():
the functionality of the dump command is now considered obsolete

- 5.005 threads are now to be considered deprecated;
the new "interpreter threads" implementation should be used instead

- Pseudohashes:
the user-visible implementation of pseudohashes is going to be removed
and replaced with something cleaner (also, the internal implementation
will have to go since it was found to slow down the overall hash access)

- Use of tainted data in exec LIST and system LIST:
now gives a warning, but will become fatal error in a future release

- tr///C, tr///U:
the interface was found to be a mistake, pack("C0", ...) and
pack("U0", ...) can be used instead

Crontab - Good Reference

2010-02-03T09:55:00.000-05:00

Crontab – Quick Reference

Setting up cron jobs in Unix and Solaris

cron is a unix, solaris utility that allows tasks to be automatically run in the background at regular intervals by the cron daemon. These tasks are often termed as cron jobs in unix , solaris. Crontab (CRON TABle) is a file which contains the schedule of cron entries to be run and at specified times.

This document covers following aspects of Unix cron jobs
1. Crontab Restrictions
2. Crontab Commands
3. Crontab file – syntax
4. Crontab Example
5. Crontab Environment
6. Disable Email
7. Generate log file for crontab activity

1. Crontab Restrictions
You can execute crontab if your name appears in the file /usr/lib/cron/cron.allow. If that file does not exist, you can use
crontab if your name does not appear in the file /usr/lib/cron/cron.deny.
If only cron.deny exists and is empty, all users can use crontab. If neither file exists, only the root user can use crontab. The allow/deny files consist of one user name per line.

2. Crontab Commands

export EDITOR=vi ;to specify a editor to open crontab file.

crontab -e Edit your crontab file, or create one if it doesn’t already exist.
crontab -l Display your crontab file.
crontab -r Remove your crontab file.
crontab -v Display the last time you edited your crontab file. (This option is only available on a few systems.)

3. Crontab file
Crontab syntax :
A crontab file has five fields for specifying day , date and time followed by the command to be run at that interval.

* * * * * command to be executed
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday=0)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)
* in the value field above means all legal values as in braces for that column.
The value column can have a * or a list of elements separated by commas. An element is either a number in the ranges shown above or two numbers in the range separated by a hyphen (meaning an inclusive range).
Notes
A. ) Repeat pattern like /2 for every 2 minutes or /10 for every 10 minutes is not supported by all operating systems. If you try to use it and crontab complains it is probably not supported.

B.) The specification of days can be made in two fields: month day and weekday. If both are specified in an entry, they are cumulative meaning both of the entries will get executed .

4. Crontab Example
A line in crontab file like below removes the tmp files from /home/someuser/tmp each day at 6:30 PM.

30 18 * * * rm /home/someuser/tmp/*

Changing the parameter values as below will cause this command to run at different time schedule below :

min hour day/month month day/week Execution time
30 0 1 1,6,12 * – 00:30 Hrs on 1st of Jan, June & Dec.
0 20 * 10 1-5 –8.00 PM every weekday (Mon-Fri) only in Oct.
0 0 1,10,15 * * – midnight on 1st ,10th & 15th of month
5,10 0 10 * 1 – At 12.05,12.10 every Monday & on 10th of every month
:
Note : If you inadvertently enter the crontab command with no argument(s), do not attempt to get out with Control-d. This removes all entries in your crontab file. Instead, exit with Control-c.

5. Crontab Environment
cron invokes the command from the user’s HOME directory with the shell, (/usr/bin/sh).
cron supplies a default environment for every shell, defining:
HOME=user’s-home-directory
LOGNAME=user’s-login-id
PATH=/usr/bin:/usr/sbin:.
SHELL=/usr/bin/sh

Users who desire to have their .profile executed must explicitly do so in the crontab entry or in a script called by the entry.

6. Disable Email
By default cron jobs sends a email to the user account executing the cronjob. If this is not needed put the following command At the end of the cron job line .

>/dev/null 2>&1

7. Generate log file
To collect the cron execution execution log in a file :

30 18 * * * rm /home/someuser/tmp/* > /home/someuser/cronlogs/clean_tmp_dir.log

Crontab

2010-02-03T09:54:00.001-05:00

Crontab – Quick Reference

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Daemon a perl process

2010-01-28T21:24:00.001-05:00

http://search.cpan.org/~ehood/Proc-Daemon-0.03/Daemon.pm

Another method:

http://www.webreference.com/perl/tutorial/9/3.html

Creating directory tree with one - mkdir -

2009-11-25T01:17:00.001-05:00

mkdir -p Deepak1/Deepak2/Deepak3/Deepak4

Network Authentication - Kerberos

2009-11-14T00:10:00.001-05:00

http://web.mit.edu/kerberos/#what_is

Solaris initialization Story

2009-11-14T00:01:00.001-05:00

The normal Unix boot process has these main phases:

Basic hardware detection (memory, disk, keyboard, mouse etc) and executing the firmware system initialization program . In Solaris, this is called Boot PROM phase. After you turn on power of the system, the PROM displays system identification information and runs self-test diagnostics to verify the system's hardware and memory.

PROM chip contains Forth OpenBoot firmware, and it is executed immediately after you turn on the system. The primary task of the OpenBoot firmware is to boot the operating system either from a mass storage device or from the network. OpenBoot contains a program called the monitor that controls the operation of the system before the kernel is available. When a system is turned on, the monitor runs a power-on self-test (POST) that checks such things as the hardware and memory on the system. If no errors are found, the automatic boot process begins. OpenBoot contains a set of instructions that locate and start up the system's boot program and eventually start up the Unix operating system.

Locating and running the initial boot program (IPL or bootloader) from a predetermined location on the disk (MBR in PC). In Solaris the primary boot program, called bootblk, is loaded from its location on the boot device (usually disk) into memory.

Locating and starting the Unix kernel. The kernel image file to execute may be determined automatically or via input to the bootloader. In Solaris the bootblk program finds and executes the secondary boot program (called ufsboot) from the Unix file system (UFS) and loads it into memory. After the ufsboot program is loaded, the ufsboot program loads the two-part kernel.

The kernel initializes itself and then performs final, high-level hardware checks, loading device drivers and/or kernel modules as required. In Solaris the kernel initializes itself and begins loading modules, using ufsboot to read the files. When the kernel has loaded enough modules to mount the root file system, it unmaps the ufsboot program and continues, using its own resources.

The kernel starts the init process, which in turn starts system processes (daemons) and initializes all active subsystems. When everything is ready, the system begins accepting user logins. In Solaris kernel starts the Unix operating system, mounts the necessary file systems, and runs /sbin/init to bring the system to the initdefault state specified in /etc/inittab. The kernel creates a user process and starts the /sbin/init process, which starts other processes by reading the /etc/inittab file. The /sbin/init process starts the run control (rc) scripts, which execute a series of other scripts. These scripts (/sbin/rc*) check and mount file systems, start various processes, and perform system maintenance tasks.

KumarDeepakRanjan.doc

2009-11-03T01:14:00.001-05:00

Kumar Deepak Ranjan

kdranjan@yahoo.com

Phone - 732 803 8761

(Permanent Resident)

SUMMARY:

Software Architect with 12 years of solid hands on experience in following domain:

Expert in OO Perl development in Business Intelligence & Web Development area.
Expert in Unix/Linux (Solaris/Redhat/Ubuntu/Debian) architecture.
Expert in Shell scripting using cut, grep/egrep, sed, awk, functions.
Oracle PL/SQL programming, Stored Procedures, Functions, Packages, Cursors, Triggers using Rapid SQL, PL/SQL Developer and Data Modeling tools like Erwin.
MySQL installation/administration and programming.
Expert Network Programming using OO Perl FTP, Telnet, SMTP etc. modules.
Expert in Data Structures such as multi-dimensional hashes, arrays, memory based DB (MLDBM, BerkeleyDB).
Good exposure to Informatica 7.1, Seibel Analytics, Cognos cube base BI systems.
Expert in installing/configuring any GNU based software on Unix/Linux platform.
Expert in Open Source Technologies. I have recommended lots of cost cutting measures in previous companies by using Open Source products.
Good knowledge in Python/Java/C/C++.
Course taken for ETL tools Informatica Power Center 7.1 & Warehouse Builder 10g.

Technical Skills:

Operating System	Solaris, Linux (Slackware, Ubuntu, Redhat), VxWorks, pSOS
Programming Languages	OO Perl, Python, Shell (csh/ksh/bash) Scripting, PHP, PL/SQL, mod_perl, HTML, JavaScript, grep, sed, awk.
Databases	Oracle 11g/10g/9i, MySQL, DBM, MLDBM, BerkeleyDB, MemCache, RRD.
Job Schedulers	Cron, kcron, autosys (d-series), Control-M
Version Control	Subversion (SVN), ClearCase
Protocol/Services	SNMP v1, v2c, v3, trap & informs, NetFlow, telnet/ssh, openSSH, openSSL, tftp, sftp, scp, rcp, rsh, UDP, TCP/IP, MIBv1 & MIBv2, ICMP, Ipv4 & Ipv6, mtop, ntop, Apache httpd, net-snmp.
Environment	kde, Gnome, CDE, VMWare, Windows
Tools	Solaris Pkgadd, pkgchk, pkgrm, swmtool, snmpd, snmptrapd, snmptt, snmpttconvertmib, Ethereal/Wireshark, MRTG, mtop, RRDtool, ObjecTime 5.2.1, Purify, Quantify, gdb/xdb, Big Brother, Hobbit Monitor, Big Brother Watcher, Configure (gnu), make (gnu), nmake, tar, deb, rpm, traceroute, tcpdump, Memcache, pgpinfo, pecl, pear, Nagios.

PROFESSIONAL EXPERIENCE:

Univision.com (July 2007 – Present)

Position: Software Architect

Environment: Solaris, Linux, Perl 5.8, Python, Oracle 9.2 & 10g, PL/SQL, sed, awk, gawk, openSSH, Multi-Threading, OO Perl DBI, DBD, MLDBM, BerkeleyDB, mod_perl, apache/perl, apache/ssl, Net::Telnet, Net::FTP, Net::Socket, Net::SSH, Net::SSL, Net::SMTP, CGI, CGI::Carp, CGI::Pretty, HTML::template, CGI::Utils, Log::Log4perl, Data::Dumper, RRDTool

Contribution:

Designed & developed the complete backend data FTP engine, Data cleansing engine, Data loading engine of CRM system (Business Intelligence) at Univision Mobile users. Designed and implemented a high performance FTP and loader engine into Dimension and fact table.
Designed and developed a complete suite of FTP and Loader Engine for Business Intelligence group, which deals mainly with Financial & Marketing (Revenue, Gross Margin, Sales, Returns, Net Margins etc.) data coming to FTP server from atleast 12 countries. FTP Engine is an ultra smart, high performance engine, which makes real time decision to FTP, files which matches the business rules. Developed re-usable perl classes/libraries. Worked with flat files, Excel files, CSV files etc.
Designed and developed lookup table comparison algorithms using perl hashes and smart algorithmic techniques.
Designed and Developed sqlldr Engine, which feeds data to staging area (Engine could load data from more than 100 flat and CSV formatted files at once.), which ultimately is loaded to Data Warehouse (DW) with the help of Loader Engine. Reporting tools Cognos takes the data to build power cubes for generating reports.
Worked with Oracle PL/SQL, Stored Procedures, Oracle Packages, Indexes, Triggers, Cursors, MySQL DB.
Designed & build a SQL engines ExecuteSQL, ExecuteBatchSQL, RunSQLBatch & RunPrjBatchSQL which executes different types of SQL packages, SQL scripts and SQL mappings in order to perform Transformation & Loading to take place.
Designed and developed an IDOL server graphing solution using RRDtool, RRDcreate, RRDupdate, RRDgraph, RRDinfo & MRTG.
Worked with ETL data modeling tools like Informatica Power Center 7.1 & OWB (Oracle Warehouse Builder) 9 and 10g. I have installed Informatica Power Center 7.1 and configured it with Oracle 10g. Worked with Informatica Repository server, Mapping Designer and Workflow Manager.
Lead the whole evaluation & decision making process of selecting a job scheduler out of Autosys’s d-series, cron, kcron, Tidal Software & Control-M. Investigated into a case study done by Gartner’s Magic quadrant to evaluate Job Scheduling product.
Developed batch scripts in k-shell & bash, which implements various dependencies between each other and configured it with automated batch processing tool Control-M.
Worked with K-shell & bash shell and used grep, egrep, sed & awk for file manipulation
Installed, Configured & used Apache 1.2 & 2.0 web server.
Worked with tools/protocols such as SNMP v1, v2c, v3, trap & informs, telnet/ssh, openSSH, openSSL, tftp, sftp, scp, rcp, rsh, UDP, TCP/IP, ICMP, Ipv4 & Ipv6, mtop, ntop, Apache Web Server, tar, deb, rpm, pkgadd, pkgrm, pkgchk,swmtool.
Worked with linux (Ubuntu 7.04 & Gutsy Gibon 7.10), Slackware & Redhat 4/5/9 as specialist.
Sound understanding of Linux/Unix kernel, different file systems.

ShoreGroup, Inc (Jan 2006 – June 2007)

Position: Senior Software Developer

ShoreGroup specializes in Systems & Network Management domain. In 2001, ShoreGroup launched a subscription-based product, CaseSentry. The CaseSentry consists of different suites of products that serve the needs of IT staff, from Network Engineers and System Administrators to the CIO/CTO of the company.

Environment: Linux, Solaris, Perl (DBI, DBD, MLDBM, Net::FTP, Net::Telnet, Net::Socket, Net::SSH, Net::SSL, sed, gawk, HTML, JavaScript, TCP/IP, UDP, SNMP, IPv4, Data Structures, Socket, POSIX Multi-threading.

Contribution:

Developed Data Collection Agent on Linux, C, C++, Data Structures and Sockets, multi-threaded programming, make, Makefile, OO Perl, JavaScript and MySQL & Sybase.
Developed a Decision Engine, in order to process SNMP traps/informs that comes in the systems DB table. DE processes the trap/inform and keeps track of the state in state machine and update status, which in turn, updates case/ticket status. Implementation involved Linux, C/C++, Perl, Data Structures and Sockets in a multi-threaded environment.
Worked with sed, grep and awk/gawk for file manipulation and scripting.
Worked in Perl scripting and development for fetching data from DB and messaging the data.
Worked with Virtual Memory and other non conventional Database like MLDBM and BerkleyDB.
Extensively supported IPCC/ICM 6.xx and ICM 7.0 SNMP trap management using SNMP (v1, v2c and v3). This feature includes implementation of IPv6 and is deployed at more than 20 customers including the ING Direct, Axis Capital, Capital One, and AXA Equitable, IRS, Verizon Wireless.
Installed and used ‘TKMIB’, a MIB browser that is a GNU based tool. Also worked with at least 100 MIBs from vendors like Cisco, Lucent, Alcatel, Juniper, Geotel, IBM, Dell, HP, Compaq etc.
Configured SNMP (v2c & v3) for Cisco IOS, CatOS, VPNs, and Firewalls.
Worked with various SNMP based tools like snmpd, snmptrapd, snmptt, and snmptthandler.
Designed and developed a web based SNMP trap manager tool that manages SNMP traps with the help of state machines. Correlated traps are fed to a Decision Engine for reporting to the support team through emails or pagers. This tool requires installation of the snmpd, snmptrapd, snmptthandler, snmpt, convertmib and snmptt tools.
Installed, set up and used the Subversion environment for version control.
Installed, created and designed a MySQL database, prepared table schemas, indexes. Wrote scripts to take database backups using mysqldump, perl & cron.
Developed a System, Application & Network monitoring product for ING Direct using open source 'Big Brother Monitor' (now owned by Quest Software, Inc), Hobbit Monitor & Big Brother Watcher.
Installed/Configured SFTP, TFTP and a GNU based tool called Pancho/Panchito & Rancid to retrieve and push configuration files for backup purposes for devices like routers, switches, VPNs, firewalls, printers, etc.
Installed/Configured APR (Apache Portable Runtime) and APR-UTIL to support installation of Subversion. Subversion's installation is dependent on APR and APR-UTIL.
Installed MTOP to monitor queries dynamically and track timing and performance of the queries in order to better optimize them.

AT&T/IBM Corporation (Aug 2001 – Dec 2005)

Position: Senior Software Engineer

Contribution:

Designed and developed a 5E simulator from scratch and supported the command response and automatic alarm systems in C, C++, Perl 5.8 (DBI, DBD, MLDBM, Net::FTP, NET::Telnet, Net::Socket etc), Data Structures, Multi-threading, Sockets, MLDBM, Berkley DB and Oracle on the HP-UX platform.
Designed and developed a DMS-100 simulator from scratch and supported the command response and automatic alarm systems in C++, Perl 5.8, Multi-threading, Sockets, MLDBM, Berkley DB and Oracle on the HP-UX platform.
Prepared the design and architecture for 15 interfaces (DBOR, FC, RUBY-CC, and RUBY-CORE) with different communication protocols that CTP will interact with. These interfaces use XML, DMQ protocol, CORBA, and LibE.
Worked with Oracle 9i PL/SQL programming language.
Designed and developed 13 interface simulators for CTP so that the tester would not have to depend on the availability of various interfaces. Used Unix, Perl, C/C++, and SQL queries extensively in this effort.
Designed and coded load balancer and performance analyzer tools in Unix and Perl that generated statistical reports for successful / failed tests conducted by a lab technician over a 24 hour period.
Used K-shell and bash shell scripting extensively in the projects.
Worked with OO Perl Development using Perl 5.6. Worked with DBD, DBI, DBM, MLDBM and BerkeleyDB.
Resolved customer problems within 24 hours of the initial call depending on the severity.
Managed resources (6 machines) and allocated them between teams. Monitored the load and build schedule.
Created test plan and test case scenarios for optimal utilization of the application.

Lucent Technology (April 2000 – July 2001)

Position: Software Developer

Lambda Xtreme is a third generation fiber optic transmission system that used optical multiplexing, optical amplification (both erbium and Raman), and optical de-multiplexing to provide high capacity, long haul reach, and ultra long haul DWDM transmission over TW-RS and most LEAF fiber types. The ultra long haul application has 10 GB/s channels that offer a 1.28 Tb/s capacity for a 4000km reach system.

Contribution:

Analyzed requirement, design and unit test specification documents for various Xtreme features. Made a tremendous contribution in the Optical Connection Directory (OPTC).
Patent Description: Method for automatically provisioning a network element. Designed and coded the Optc and Channel Map in C++ using ObjecTime 5.1. [Google 'Patent Search' KeyWord: 6920288].
Developed backend TL1 commands that worked between the GUI and Network Element.
Prepared the test bed in a lab environment for simulating reaches of 500 miles and longer.
Helped the system integration team load the software into field boxes and perform tests in real world scenarios.
Managed software configurations using ClearCase & DDTS.
Installed a Cisco router (2600) in the Lucent Laboratory for the system integration team.

TCS-Nortel (Sept 1997 – March 2000)

Position: Assistant System Analyst

Projects:

Communication Assistance for Law Enforcement Agency (CALEA): This feature provides the packet interception facility for ISDN packet calls. All the packets that are transmitted and received by the suspect are intercepted, copied and delivered to the Law Enforcement Agency's DTE. This feature was developed for the FBI, USA. (Please check out www.FBI.gov for a brief description of this feature)

X.25 User Loop back (Echo Station): The aim of this feature was to provide the end-user (the ISDN subscriber) with the ability to verify the communication link from his DTE to the switch by dialing a directory number provided by the Telco (Telephone Operating Companies).

Contribution:

Analyzed requirements and software design for various projects based on ISDN BRI packet switching in layer 2 and layer 3 (XLIU Call Processing & Provisioning).

Designed, prototyped and coded Layer 3 software for DMS-100 switches.

Prepared system test case documentation for multiple features.

Participated in a team of six (6) while learning the software life cycle (requirements analysis, high level design, low level design, prototyping, coding and testing).

EDUCATION:

B.E. (Electrical Engineering) National Institute of Technology (REC), Jamshedpur, India

Accomplishments:

Brain Bench Certified (2008) OO Perl 5.8 developer.

Ranked top 1^% in the National Physics competition conducted by I.I.T, Kanpur, India.
Worked on implementing Patent IDS #6920288 at Alcatel-Lucent.
Got recommendations from managers and directors at previously held positions.

Embedding Perl in HTML with Mason

2009-10-28T00:48:00.000-04:00

This book is available for free @_ http://www.masonbook.com/book/

Perl Inheritance Simplified

2009-10-20T00:37:00.000-04:00

http://perl.active-venture.com/pod/perltoot-inheritance.html

Perl Special Literals list

2009-10-09T11:11:00.002-04:00

__FILE__ = represent the current filename
__LINE__ = line number
__PACKAGE__ package name

If there is no current package (due to an empty package; directive),
__PACKAGE__ is the undefined value.

The two control characters ^D and ^Z, and the tokens __END__ and __DATA__ may be used to indicate the logical end of the script before the actual end of file. Any following text is ignored.

Text after __DATA__ may be read via the filehandle PACKNAME::DATA, where PACKNAME is the package that was current when the __DATA__ token was encountered. The filehandle is left open pointing to the contents after __DATA__. It is the program's responsibility to close DATA when it is done reading from it. For compatibility with older scripts written before __DATA__ was introduced, __END__ behaves like __DATA__ in the top level script (but not in files loaded with require or do) and leaves the remaining contents of the file accessible via main::DATA.

See SelfLoader for more description of __DATA__, and an example of its use. Note that you cannot read from the DATA filehandle in a BEGIN block: the BEGIN block is executed as soon as it is seen (during compilation), at which point the corresponding __DATA__ (or __END__) token has not yet been seen

How to determine Total memory (Total RAM, Used RAM, Free RAM) on Unix/Linux

2009-10-02T00:14:00.002-04:00

'free' tool prints pretty much everything.

total used free shared buffers cached
Mem: 514592 274136 240456 0 20228 134104
-/+ buffers/cache: 119804 394788
Swap: 1052216 0 1052216

or

cat /etc/meminfo - has all the information.

How to find out which process is listening upon a port

2009-10-01T23:41:00.002-04:00

For standard processes, Services names can be seen in /etc/services files associated with port numbers. This is pretty much standard TCP/IP.

For non-standard user defined services,

lsof -i :port_number

For example:

So to see which process is listening upon port 80 we can run:

root@mystery:~# lsof -i :80
This gives us the following output:

COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
apache2 10437 root 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10438 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10439 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10440 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10441 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10442 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 25966 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 25968 www-data 3u IPv6 22890556 TCP *:www (LISTEN)

Best practices for a high performance Perl program

2009-05-14T13:44:00.001-04:00

http://makepp.sourceforge.net/1.50/perl_performance.html

Validating data types in PERL

2009-03-04T13:49:00.002-05:00

Since perl data types are very typeless and depends upon where they are used. There are some situations, when this design is awkward.

To validate data types,

Data::Types module can be installed and used.

However if you dont want to install, here are few quickies:

- To Check

% An Integer, Use regex /^[+-]?\d+$/ and ofcourse, not matched ones are non-intger
% A Decimal, /^[+-]?(?:\d+(?:\.\d*)?|\.\d+)$/
% Whole number, /^\d+$/
% Float number, /^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/
%

Python Advance books

2009-02-25T11:03:00.000-05:00

A Good link for description of these books.

http://wiki.python.org/moin/AdvancedBooks

How to group UNIX Solaris, Linux commands

2008-11-24T12:54:00.002-05:00

Simply group them in a small bracket and separate them by semi colon (;)

123-bash: (ls -1;pwd;cd /tmp/curl)

It will list the files in CWD first, print the directory you are in, cd to /tmp/curl

How to get user input in PERL

2008-11-18T15:22:00.002-05:00

It's simple -

- The angle bracket operator to read from STDIN (see I/O operators in perlop)
- If entering 'Y' or 'N' - make sure to use 'chomp' to cut the new line character.
- @ARGV - the array that holds parameters from the command line (see perlvar)
- Getopt::Long or Getopt::Std - for more powerful handling of command line arguments
- uc - to uppercase an expression
- ucfirst - to uppercase the first letter of an expression

Later in your code, you can compare by using 'eq' or 'ne' or '==' or '!=' or
pattern matching =~ m///, thingy to move on to do what you want.....

Solaris Kernel Modules operations

2008-11-14T16:26:00.002-05:00

Kernel Modules:
---------------

modinfo : prints out information on all currently loaded kernel modules.
modload : loads kernel modules.
modunload : unloads kernel modules.
forceload : in the /etc/system file loads a module at boot time.

Passing a DB handler to an user defined function

2008-11-10T13:53:00.001-05:00

It is pretty simply. Pass it like an ordinary variable.

Example here:

#!/opt/local/bin/perl

use db_connect;
use warnings;
use strict;

# More efficient than ./test_connection.pl because $0 makes only one DB connection

my $obj = db_connect->new();
my $db = $obj->connect_qora007_mir("qora007_mir");

print " \n";
&checkConnectionMIR_qora007($db);
&checkConnectionCIR_qora007($db);
print " \n";

$db->disconnect();

sub checkConnectionMIR_qora007($)
{
my $dbh = shift;

my $sql;
my $sth;
my $str;
my @row;

$sql = "select sysdate from dual";

$sth = $dbh->prepare($sql);
$sth->execute;

while((@row) = $sth->fetchrow_array())
{
$str = join(" " , map {defined $_ ? $_ : "(null)"} @row);
print "INSTANCE: $str\n";
}

PERL - IF ELSE statement shortcuts

2008-11-06T15:27:00.002-05:00

I will give an example of how to write IF ELSE statement in short. This will be simply useful to read others code if you know that this can also be an option. This kind of code normally comes from seasoned PERL programers.

#!/opt/local/bin/perl

use warnings;
use strict;

print &max(5, 3);
print &max(7, 10);

sub max (@)
{
my ($x, $y) = @_;
return $x > $y ? $x : $y;
}

Explanation: In function max, 2nd lines means that

if $x is greater than $y, return $x or return $y. That's it.....

How to open a write into an already zipped file in perl:

2008-11-05T11:40:00.001-05:00

How to open a write into an already zipped file in perl:
--------------------------------------------------------

my $temp_file = "file_name.gz";
open(HWRITE, "|gzip -c > $temp_file") or die "cannot open file $temp_file\n";
print HWRITE "Something_1|Something_1|Something_1|Something_1\n"
or die "File write failed : $!\n";

How to pass an object in a function

2008-10-10T13:42:00.002-04:00

It is really simple concept but can confuse novice to perl. An object can be passed to a function just like an ordinary variable. File handler need special syntax to be
passed inside a function but not an object.

Follow this simple example here. Code is incomplete but is tested when complete.

Here it goes:

#!/opt/local/bin/perl

use lib "$ENV{HOME}/perl/lib";
use convert_time;
use dir_pool;
use db_connect;
use warnings;
use strict;

my $obj = db_connect->new();

&doConnectMIR($obj);
print " \n";
&doConnectCIR($obj);

sub doConnectMIR($)
{
my $tObj = shift;

my $dbh;
my $sql;
my $sth;
my $str;
my @row;

$tObj = db_connect->new();
$dbh = $obj->connect_qora007_mir("qora007_mir");

$sql = "select sysdate from dual";

$sth = $dbh->prepare($sql);
$sth->execute;

while((@row) = $sth->fetchrow_array())
{
$str = join(" " , map {defined $_ ? $_ : "(null)"} @row);
print "INSTANCE: $str\n";
}

more code follows.....but concept is clear.....

Typical Oracle profile file on Unix

2008-08-20T10:30:00.001-04:00

# .oracle10g

### Oracle specific setup
ORACLE_HOME=/opt/oracle10g/instantclient_10_2
TNS_ADMIN=/opt/oracle10g/instantclient_10_2
NLS_LANG=_.WE8ISO8859P1

export ORACLE_HOME TNS_ADMIN NLS_LANG

LD_LIBRARY_PATH=$ORACLE_HOME:$LD_LIBRARY_PATH
export LD_LIBRARY_PATH
PATH=$ORACLE_HOME:$PATH

export PATH
### End Oracle specific setup

Typical Oracle profile file on Unix

2008-08-20T10:30:00.000-04:00

Perl Internals - Simon Cozens

2008-08-01T10:32:00.000-04:00

http://www.faqs.org/docs/perl5int/

How Hashes Really Work

2008-08-01T10:26:00.001-04:00

Great article to understand Hashes in PERL

PERL - How to use %INC & @INC on command line

2008-07-24T16:50:00.002-04:00

perl -e 'use XML::Simple;use XML::Parser; foreach my $tuni (keys %INC){print $tuni . "\t" . $INC{$tuni} . "\n"}'

perl -e 'print "@INC\n"'

Multiple -e can be used, just like shell's sed program.

Unix - Large file aware utilities

2008-07-09T13:17:00.000-04:00

A large file is a regular file whose size is greater than or
equal to 2 Gbyte ( 2**31 bytes). A small file is a regular
file whose size is less than 2 Gbyte.

Large file aware utilities
A utility is called large file aware if it can process large
files in the same manner as it does small files. A utility
that is large file aware is able to handle large files as
input and generate as output large files that are being pro-
cessed. The exception is where additional files are used as
system configuration files or support files that can augment
the processing.

For example, the file utility supports the
-m option for an alternative "magic" file and the -f option
for a support file that can contain a list of file names. It
is unspecified whether a utility that is large file aware
will accept configuration or support files that are large
files. If a large file aware utility does not accept confi-
guration or support files that are large files, it will
cause no data loss or corruption upon encountering such
files and will return an appropriate error.

The following /usr/bin utilities are large file aware:

adb awk bdiff cat chgrp
chmod chown cksum cmp compress
cp csh csplit cut dd
dircmp du egrep fgrep file
find ftp getconf grep gzip
head join jsh ksh ln
ls mdb mkdir mkfifo more
mv nawk page paste pathchck
pg rcp remsh rksh rm
rmdir rsh sed sh sort
split sum tail tar tee
test touch tr uncompress uudecode
uuencode wc zcat

The following /usr/xpg4/bin utilities are large file aware:

awk cp chgrp chown du
egrep fgrep file grep ln
ls more mv rm sed
sh sort tail tr

The following /usr/sbin utilities are large file aware:

install mkfile mknod mvdir swap

Knowledge about pixel, resolution and how to convert pixel into inches

2008-07-02T13:26:00.003-04:00

Folks,
Recently I got to work with GD library using PHP 5.xx and was little confused about pixels, resolution and how to convert them into physical dimensional measurement units like centimeters or inches.

I think, lots of people are still very confused about it but still work as developers in GUI or web development.

Here is some information......

Say, there is an image of a flower 400x300 pixels. It means that height of this image is 400 pixel and width is 300 pixels. With it, there must be one more attribute of screen called 'resolution' (Remember, your color TV resolution).
Say that is 72 ppi (pixel per inch).

Simple mathematics: 72 ppi means
72 pixels in 1 inch
Therefore, 400 pixels in = 400/72 = 5.55 inches tall
Therefore, 300 pixels in = 300/72 = 4.16 inches wide

Hope it clears the cloud.

How to convert seconds into HH:MM:SS (24 hour format)

2008-07-01T16:05:00.001-04:00

// $startstamp, $endstamp are both UNIX timestamp
// from Jan 1, 1970 mid night

function elapsed_time($startstamp, $endstamp)
{
$sec=$endstamp - $startstamp;

$hours = ($sec/3600);
list($hours, $x) = split('\.', $hours);
if ($hours < 10)
{
$hours = "0" . $hours;
}

$min = ($sec%3600);
$min = ($min/60);
list($min, $x) = split('\.', $min);
if ($min < 10)
{
$min = "0" . $min;
}

$sec = ($sec%60);
if ($sec < 10)
{
$sec = "0" . $sec;
}

return "$hours:$min:$sec";

}

MySQL - Convert MySQL date, datetime, timestamp to unix time and Vice versa

2008-06-19T16:35:00.003-04:00

&& To convert Unix time to regular MySQL DATETIME
select from_unixtime('1213907115');
It prints '2008-06-19 16:25:15'

&& To Convert DATETIME to unixtime
select unix_timestamp('2008-06-19 16:25:15');
It prints 1213907115

&& To Convert current date & time to unix time.
select unix_timestamp();

&& To Convert a column of DATETIME type to unixtime.
select unix_timestamp(c8013_date_created) from RealTimeStatus.T8013_PROGRAM;

PERL - Hash, Hash reference and file handler passing to a subroutines

2008-06-12T16:51:00.003-04:00

Fews days ago - One of my friends asked me about:
1. hashes in perl
2. hash references and how to use them
3. file handler passing to a subroutines....

Here is an example.....

#!/opt/local/bin/perl

use warnings;
use strict;

my $n_ref;
my $p_ref;

open(NAME, "./tns_names") or die " Failed to open tns_names file : $! \n ";
open(PASS, "./tns_pass") or die " Failed to open tns_pass file : $! \n ";

$n_ref = &process_names(*NAME);
$p_ref = &process_pass(*PASS);

&do_final($n_ref, $p_ref);

close NAME;
close PASS;

sub process_names($)
{
local *h = shift;

my %n;
my $nkey;
my $nval;

while()
{
chomp $_;
($nkey, $nval) = split(/,/, $_);
$n{$nkey} = $nval;
}
return \%n;
}

sub process_pass($)
{
local *h = shift;

my %p;
my $pkey;
my $pval;

while()
{
chomp $_;
($pkey, $pval) = split(/,/, $_);
$p{$pkey} = $pval;
}
return \%p;
}

sub do_final(@)
{
my ($nam, $pas) = @_;
my $akey;

foreach $akey (keys %$nam)
{
print 'Key :' . $akey . ' and Value: ' . $nam->{$akey} . "\n";
}

foreach $akey (keys %$pas)
{
print 'Key :' . $akey . ' and Value: ' . $pas->{$akey} . "\n";
}
}

1;

PERL - I/O Redirection Example

2008-06-12T16:19:00.000-04:00

The following example shows how I/O can be simply redirected:

open(F, '>/tmp/x') || die;
*STDOUT = *F;
print "hello world\n";

The print function thinks it is sending the output to STDOUT but ends up sending it to the open file instead, because the typeglob associated with STDOUT has been aliased to F. If you want this redirection to be temporary, you can localize *STDOUT.

PERL - Passing Filehandles to Subroutines

2008-06-12T16:18:00.001-04:00

#!/usr/bin/perl
use warnings;
use strict;

open(NAME, "./names") or die " Failed to open tns_names file : $! \n ";
open(PASS, "./pass") or die " Failed to open tns_pass file : $! \n ";

&process_names(*NAME);
&process_pass(*PASS);

close NAME;
close PASS;

sub process_names($)
{
local (*h) = shift;
while()
{
chomp $_;
print $_ . "\n";
}

}

sub process_pass($)
{
local (*h) = shift;
while()
{
chomp $_;
print $_ . "\n";
}
}

How to install ‘mysql-server’ community 5.1 and client on RHEL 5.0

2008-06-06T13:54:00.001-04:00

How to install ‘mysql-server’ community 5.1 and client on RHEL 5.0

Step 1:

First step is to check if there are any version of mysql already installed. This is due to the fact that RHEL has some default packages available already. Do this.

rpm –qa |grep mysql
mysql-connector-odbc-3.51.12-2.2
MySQL-python-1.2.1-1
mysql-5.0.45-7.el5
perl-DBD-MySQL-3.0007-1.fc6
libdbi-dbd-mysql-0.8.1a-1.2.2
mysql-server-5.0.45-7.el5

Printed are a list of mysql server installed, clients and drivers like perl DBD driver, python driver and other stuff. Best idea is to get rid of all these dependencies and build it again. That can be done by

rpm –e < mysql-server-5.0.45-7.el5>
rpm –e < libdbi-dbd-mysql-0.8.1a-1.2.2
…..and so on.

Step 2:

Try installing MySQL server 5.1 from MySQL mirror website itself. It would automatically start the server once successfully installed. ‘root’ is the default user id with a blank password. Root’s password can be changed once client package is installed which includs mysql and mysqladmin and other administrative tools.

rpm –i http://dev.mysql.com/get/Downloads/MySQL-5.1/MySQL-server-community-5.1.24-0.rhel5.i386.rpm/from/http://mirror.trouble-free.net/mysql_mirror/

Step 3:

Try installing MySQL clients packages which include administrative tools like mysql, mysqladmin, mysqldump and others…..

rpm –i http://dev.mysql.com/get/Downloads/MySQL-5.1/MySQL-client-community-5.1.24-0.rhel5.i386.rpm/from/http://mirror.trouble-free.net/mysql_mirror/

Step 4:

Change root user password or simply execute /usr/bin/mysql_secure_installation. Answer all the questions appropriately. That’s it.

Step 5:

Check if mysql is running by doing: ps –eaf|grep mysqld

Also try connecting to it by doing.
mysql –uroot –p
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 38
Server version: 5.1.24-rc-community MySQL Community Server (GPL)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| mysqlDB |
| test |
+--------------------+
4 rows in set (0.00 sec)

====== Now, you are all set =====================

DO NOT FORGET TO RE-INSTALL DRIVERS FOR CLIENTS LIKE PERL, PYTHON, PHP.

How to install 'MySQL' driver on Solaris platform

2008-06-06T13:31:00.001-04:00

How to install 'MySQL' driver on Solaris platform:
-------------------------------------------------

STEP 1:

Download DBD-mysql-4.007.tar.gz http://search.cpan.org/dist/DBD-mysql/lib/DBD/mysql.pm
by using wget tool from unix10/unix22 boxes because ftp/telnet/scp/sftp is prohibited.

STEP 2:

Copy this file into /tmp/mysql ( Create a temporary directory mysql under /tmp )

STEP 3:

gzip -d DBD-mysql-4.007.tar.gz

STEP 4:

tar xvf DBD-mysql-4.007.tar

STEP 5:

cd DBD-mysql-4.007

STEP 6:

perl Makefile.PL --libs="-L/usr/local/mysql/lib/mysql -lmysqlclient -lz" \
--cflags=-I/usr/local/mysql/include/mysql

STEP 7:

make
make install

STEP 8: mysql driver has been installed if 'make install' does not produce any errors.

STEP 9: How to verify if - mysql driver is installed.

Used this perl script to verify:

#!/opt/local/bin/perl -w

use strict;
use DBI;

$|=1;
my @x_drivers = DBI->available_drivers();
foreach (@x_drivers){ print $_ . "\n";}

__END__

How to install mtop for MySQL on RHEL 5.0 machine

2008-06-06T13:17:00.001-04:00

How to install mtop for MySQL on RHEL 5.0 machine:

Step 1: Download
wget http://downloads.sourceforge.net/mtop/mtop0.6.6.tar.gz?modtime=1094947200&big_mirror=0

Step 2: unzip it.
gzip -d mtop-0.6.6.tar.gz

Step 3: Extract the files
tar xvf mtop-0.6.6.tar

NOTE: It will create a directory named ‘mtop-0.6.6’

Step 4: Install it.
mtop-0.6.6
perl Makefile.PL
sudo make
sudo make install

mtop is installed. If ‘which mtop’ is done, it will print
/usr/local/bin/mtop

Where to download mtop from - if unix/linux boxes can not connect to your windows

2008-06-05T15:33:00.002-04:00

Folks,

For most of us, Unix/Linux (Dev/QA) environment is totally separate from our work machine which should be most likely windows boxes and basically users use putty, or something like that. What if network does not allow you to copy or ftp/sftp
anything from your windows box to Unix/Linux boxes.

Simply use this on your unix machine:
wget http://search.cpan.org/CPAN/authors/id/M/MP/MPREWITT/mtop/mtop-0.6.4.tar.gz

Convert character sets from UTF8 to Latin1 and Base64

2008-06-05T14:49:00.002-04:00

Folks,
I came across this learning during some work where I have to convert some utf8 based characters from database to latin1 and some cases vice versa.....

Perl site has good demo of this. Check this out...

http://perldoc.perl.org/Encode/Encoder.html.

This can also convert Latin1 to base64 and vice versa....

Pretty cool stuff.

How to know, which all DBD exists on a Unix/Linux platform

2008-05-29T09:32:00.001-04:00

#!/opt/local/bin/perl

## How to know, which all DBD exists on a Unix/Linux platform.

use warnings;
use strict;
use DBI;

my @xt=DBI->available_drivers();
foreach (@xt)
{
print $_ . "\n";
}

UNIX shell differences and how to change your shell

2008-05-28T13:40:00.000-04:00

The following article answers the frequently asked questions, what
UNIX shells are available, what are the differences between them and
how do you change your interactive shell. It is posted monthly to the
USENET newsgroups comp.unix.shell, comp.unix.questions, news.answers
and comp.answers and is additionally available on the world wide web
as http://www.wonderland.org/~eternal/shell.html

Contents

* Modifications since last issue
* Why change your shell
* The history of unix shells
* Deciding on a shell
* Shell features (table)
* How to change your shell
* A warning about changing your shell
* Further information
* Copyright and Disclaimer

Modifications since last issue

* Change of authors contact addresses

Why change your shell

The UNIX shell is most people's main access to the UNIX operating
system and as such any improvement to it can result in considerably
more effective use of the system, and may even allow you to do things
you couldn't do before. The primary improvement most of the new
generation shells give you is increased speed. They require fewer key
strokes to get the same results due to their completion features, they
give you more information (e.g. showing your directory in your prompt,
showing which files it would complete) and they cover some of the more
annoying features of UNIX, such as not going back up symbolic links to
directories.

A brief history of UNIX shells

Note, this history is just known to be slightly out of historical
order, it is in the process of being corrected, but for the moment
should be taken with a pinch of salt

In the near beginning there was the Bourne shell /bin/sh (written by
S. R. Bourne). It had (and still does) a very strong powerful
syntactical language built into it, with all the features that are
commonly considered to produce structured programs; it has
particularly strong provisions for controlling input and output and in
its expression matching facilities. But no matter how strong its input
language is, it had one major drawback; it made nearly no concessions
to the interactive user (the only real concession being the use of
shell functions and these were only added later) and so there was a
gap for something better.

Along came the people from UCB and the C-shell /bin/csh was born. Into
this shell they put several concepts which were new, (the majority of
these being job control and aliasing) and managed to produce a shell
that was much better for interactive use. But as well as improving the
shell for interactive use they also threw out the baby with the bath
water and went for a different input language.

The theory behind the change was fairly good, the new input language
was to resemble C, the language in which UNIX itself was written, but
they made a complete mess of implementing it. Out went the good
control of input and output and in came the bugs. The new shell was
simply too buggy to produce robust shell scripts and so everybody
stayed with the Bourne shell for that, but it was considerably better
for interactive use so changed to the C shell, this resulted in the
stupid situation where people use a different shell for interactive
work than for non-interactive, a situation which a large number of
people still find themselves in today.

After csh was let loose on an unsuspecting world various people
decided that the bugs really should get fixed, and while they where at
it they might as well add some extra features. In came command line
editing, TENEX-style completion and several other features. Out went
most of the bugs, but did the various UNIX operating system
manufacturers start shipping tcsh instead of csh? No, most of them
stuck with the standard C-Shell, adding non-standard features as they
went along.

Eventually David Korn from AT&T had the bright idea to sort out this
mess and the Korn shell /bin/ksh made its appearance. This quite
sensibly junked the C shells language and reverted back to the bourne
shell language, but it also added in the many features that made the C
shell good for interactive work (you could say it was the best of both
worlds), on top of this, it also added a some features from other
operating. The Korn shell became part of System V but had one major
problem; unlike the rest of the UNIX shells it wasn't free, you had to
pay AT&T for it.

It was at about this time that the first attempts to standardize UNIX
started in the form of the POSIX standard. POSIX specified more or
less the System V Bourne Shell (by this time the BSD and System V
versions had got slightly different). Later the standard is upgraded,
and somehow the new standard managed to look very much like ksh.

Also at about this time the GNU project was underway and they decided
that they needed a free shell, they also decided that they wanted to
make this new shell POSIX compatible, thus bash (the Bourne again
shell) was born. Like the Korn shell bash was based upon the Bourne
shells language and like the Korn shell, it also pinched features from
the C shell and other operating systems (in my opinion it put them
together better; guess which shell I use), but unlike the Korn shell
it is free. Bash was quickly adopted for LINUX (where it can be
configured to perform just like the Bourne shell), and is the most
popular of the free new generation shells.

Meanwhile Tom Duff faced with the problem of porting the Bourne shell
to Plan 9, revolts and writes rc instead, he publishes a paper on it,
and Byron Rakitzis reimplements it under UNIX. With the benefit of a
clean start Rc ended up smalled, simpler, more regular and in most
peoples opinion a much cleaner shell.

The search for the perfect shell still goes on and the latest entry
into this arena is zsh. Zsh was written by Paul Falstad while he was a
student a Princeton and suffers from slight case of feeping
creaturism. It is based roughly on the bourne shell (although there
are some minor but important differences) and has so many additional
features that I don't even think the author even knows all of them.

Additionally rc has been enhanced to produced es, this shell adds the
ability for the user to redefine low level functions.

Deciding on a shell

Which of the many shells you choose depends on many different things,
here is what I consider to be the most important, you may think
differently.

How much time do I have to learn a new shell?
There is no point in using a shell with a different syntax, or
a completly different alias system if you havn't the time to
learn it. If you have the time and are presently using csh or
tcsh it is worth considering a switch to a Bourne shell
variant.

What do I wish to be able to do with my new shell?
The main reason for switching shells is to gain extra
functionality; its vital you know what you are gaining from the
switch.

Do I have to be able to switch back to a different shell?
If you may have to switch back to a standard shell, it is
fairly important you don't become too dependent on extra
features and so can't use an older shell.

How much extra load can the system cope with?
The more advanced shells tend to take up extra CPU, since they
work in cbreak mode; if you are on an overloaded machine they
should probably be avoided; this can also cause problems with
an overloaded network. This only really applies to very old
systems nowadays.

What support is given for my new shell?
If your new shell is not supported make sure you have someone
you can ask if you encounter problems or that you have the time
to sort them out yourself.

What shell am I using already?
Switching between certain shells of the same syntax is alot
easier than switching between shells of a different syntax. So
if you havn't much time a simple upgrade (eg csh to tcsh) may
be a good idea.

Can I afford any minor bugs?
Like most software all shells have some bugs in them
(especially csh), can you afford the problems that may occur
because of them.

Do you need to be able to use more than one shell?
If you use more than one machine you may discover that you need
to use more than one shell regularly. How different are these
shells and can you cope with having to switch between these
shells on a regular basis. It may be to your advantage to
choose shells that are similar to each other.

Shell features

This table below lists most features that I think would make you
choose one shell over another. It is not intended to be a definitive
list and does not include every single possible feature for every
single possible shell. A feature is only considered to be in a shell
if in the version that comes with the operating system, or if it is
available as compiled directly from the standard distribution. In
particular the C shell specified below is that available on SUNOS 4.*,
a considerable number of vendors now ship either tcsh or their own
enhanced C shell instead (they don't always make it obvious that they
are shipping tcsh.

sh csh ksh bash tcsh zsh rc es
Job control N Y Y Y Y Y N N
Aliases N Y Y Y Y Y N N
Shell functions Y(1) N Y Y N Y Y Y
"Sensible" Input/Output redirection Y N Y Y N Y Y Y
Directory stack N Y Y Y Y Y F F
Command history N Y Y Y Y Y L L
Command line editing N N Y Y Y Y L L
Vi Command line editing N N Y Y Y(3) Y L L
Emacs Command line editing N N Y Y Y Y L L
Rebindable Command line editing N N N Y Y Y L L
User name look up N Y Y Y Y Y L L
Login/Logout watching N N N N Y Y F F
Filename completion N Y(1) Y Y Y Y L L
Username completion N Y(2) Y Y Y Y L L
Hostname completion N Y(2) Y Y Y Y L L
History completion N N N Y Y Y L L
Fully programmable Completion N N N N Y Y N N
Mh Mailbox completion N N N N(4) N(6) N(6) N N
Co Processes N N Y N N Y N N
Builtin artithmetic evaluation N Y Y Y Y Y N N
Can follow symbolic links invisibly N N Y Y Y Y N N
Periodic command execution N N N N Y Y N N
Custom Prompt (easily) N N Y Y Y Y Y Y
Sun Keyboard Hack N N N N N Y N N
Spelling Correction N N N N Y Y N N
Process Substitution N N N Y(2) N Y Y Y
Underlying Syntax sh csh sh sh csh sh rc rc
Freely Available N N N(5) Y Y Y Y Y
Checks Mailbox N Y Y Y Y Y F F
Tty Sanity Checking N N N N Y Y N N
Can cope with large argument lists Y N Y Y Y Y Y Y
Has non-interactive startup file N Y Y(7) Y(7) Y Y N N
Has non-login startup file N Y Y(7) Y Y Y N N
Can avoid user startup files N Y N Y N Y Y Y
Can specify startup file N N Y Y N N N N
Low level command redefinition N N N N N N N Y
Has anonymous functions N N N N N N Y Y
List Variables N Y Y N Y Y Y Y
Full signal trap handling Y N Y Y N Y Y Y
File no clobber ability N Y Y Y Y Y N F
Local variables N N Y Y N Y Y Y
Lexically scoped variables N N N N N N N Y
Exceptions N N N N N N N Y

Key to the table above.

Y Feature can be done using this shell.

N Feature is not present in the shell.

F Feature can only be done by using the shells function
mechanism.

L The readline library must be linked into the shell to enable
this Feature.

Notes to the table above

1. This feature was not in the orginal version, but has since become
almost standard.
2. This feature is fairly new and so is often not found on many
versions of the shell, it is gradually making its way into
standard distribution.
3. The Vi emulation of this shell is thought by many to be
incomplete.
4. This feature is not standard but unoffical patches exist to
perform this.
5. A version called 'pdksh' is freely available, but does not have
the full functionality of the AT&T version.
6. This can be done via the shells programmable completion mechanism.
7. Only by specifing a file via the ENV environment variable.

How to change your shell

If you ever look at a UNIX manual page it will say that to change your
shell use chsh or passwd -s; unfortunately it often isn't as simple as
this, since it requires that your new shell is recognized as a valid
shell by the system and at present many systems do not recognize the
newer shells (the normal selection is, /bin/sh, /bin/csh and possibly
/bin/ksh). You are thus left with having to do some sort of fudge,
changing your effective login shell without changing your official
entry in /etc/passwd. You may also be left with the problem that there
isn't a compiled binary on your system , so you will have to get hold
of the shell's source and compile it yourself (Its generally best to
ask around to see if anyones done this already, since it isn't that
easy). Once done you should add in code to your old shells login file
so that it overlays your official login shell with your new shell
(remember to add the login flags to the command line, and with
csh/tcsh ensure that the overlay doesn't happen recursively since they
both read the same .login file).

The shell can be recognized as a valid shell if the system
administrator puts it in the file /etc/shells. If this file does not
exist, it must be created and should contain all valid shells
(i.e.don't forget the traditional ones in all their forms).

WARNING

If you do decide to change your shell you must be very careful - if
handled wrongly it can be almost impossible to correct, and will
almost certainly cause you a lot of hassle. Never make a new shell a
login shell until you have tested its new configuration files
thoroughly and then tested them once again. It is also important that
you make a full backup of your previous config files onto a floppy
disk (or a different host if you have a second account) if you have to
change any of them (which you will probably have to do if you can't
change your shell entry in /etc/passwd). You should also note that
your new shell is probably not supported by your system admin, so if
you have any problems you will probably have to look elsewhere.

Further information

The Bourne shell, the C-Shell and the Korn Shell (if you have it) are
all distributed as standard with your UNIX operating system,
information on these should come with your operating system, bug
reports etc should be sent to your operating system vendor. The free
version of ksh, pdksh is available as ftp://ftp.cs.mun.ca/pub/pdksh/

A commercial "compiler" (CCsh) is available for the Bourne shell, this
can provide extra speed on some applications. For more information
contact Comeau Computing 91-34 120th Street, Richmond Hill, NY, USA
11418-3214. Email comeau@csanta.attmail.com.

Bash was written and is maintained by the Free Software Foundation,
the primary source of information for this shell is its manual page.
Bug reports should be sent to bash-maintainers@ai.MIT.Edu, while
suggestions and philosophical bug reports may be mailed to
bug-bash@ai.MIT.Edu or posted to the Usenet newsgroup gnu.bash.bug,
the source is widely available on many ftp sites, and is subject to
the GNU copyleft licence.

Tcsh is available by ftp from ftp://ftp.deshaw.com and several other
places.

Rc is available by ftp from ftp://viz.tamu.edu/pub/rc,
ftp://ftp.sys.utotonoto.cs/pub/rc and several other places. An FAQ
exists and is posted frequently to comp.unix.shell and other places.
The Rc mailing list may be subscribed to by sending mail to
rc-request@hawkwind.utcs.toronto.edu, this, the manual page and the Rc
FAQ are the main sources of information for this shell. The original
paper on rc is available as
http://plan9.att.com/plan9/plan9doc/7.ps.Z.

Zsh is available by ftp from ftp://ftp.math.gatech.edu/pub/zsh and at
several mirror sites. Zsh is now maintained by the members of the zsh
mailing lists, which can be subscribed to by sending email to
zsh-announce-request@math.gatech.edu (announcements),
zsh-users-request@math.gatech.edu (users discussions) or
zsh-workers-request@math.gatech.edu (zsh hacking and development) with
a subject of "subscribe email-address", there is also an FAQ which
is posted frequently to comp.unix.shell. The manual page, the Z-shell
FAQ and the zsh-list are the main sources of information for this
shell.

ES is available by ftp from ftp://ftp.cs.utoronto/pub/es and at
several other places, a mailing list can be subscribed to by sending
mail to es-request@hawkwind.utcs.toronto.edu and a paper about es is
at http://www.webcom.com/~haahr/es/es-usenix-winter93.html.

Questions on any of the UNIX shells and on shell script programming,
may be posted to the Usenet newsgroup comp.unix.shell a quick response
can normally be expected, especially on subjects relating to the more
common shells.

BASH Frequently-Asked Questions

2008-05-28T13:34:00.000-04:00

This is the Bash FAQ, version 3.26, for Bash version 2.05b.

This document contains a set of frequently-asked questions concerning
Bash, the GNU Bourne-Again Shell. Bash is a freely-available command
interpreter with advanced features for both interactive use and shell
programming.

Another good source of basic information about shells is the collection
of FAQ articles periodically posted to comp.unix.shell.

Questions and comments concerning this document should be sent to
chet@po.cwru.edu.

This document is available for anonymous FTP with the URL

ftp://ftp.cwru.edu/pub/bash/FAQ

The Bash home page is http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html

----------
Contents:

Section A: The Basics

A1) What is it?
A2) What's the latest version?
A3) Where can I get it?
A4) On what machines will bash run?
A5) Will bash run on operating systems other than Unix?
A6) How can I build bash with gcc?
A7) How can I make bash my login shell?
A8) I just changed my login shell to bash, and now I can't FTP into my
machine. Why not?
A9) What's the `POSIX Shell and Utilities standard'?
A10) What is the bash `posix mode'?

Section B: The latest version

B1) What's new in version 2.05b?
B2) Are there any user-visible incompatibilities between bash-2.05b and
bash-1.14.7?

Section C: Differences from other Unix shells

C1) How does bash differ from sh, the Bourne shell?
C2) How does bash differ from the Korn shell, version ksh88?
C3) Which new features in ksh-93 are not in bash, and which are?

Section D: Why does bash do some things differently than other Unix shells?

D1) Why does bash run a different version of `command' than
`which command' says it will?
D2) Why doesn't bash treat brace expansions exactly like csh?
D3) Why doesn't bash have csh variable modifiers?
D4) How can I make my csh aliases work when I convert to bash?
D5) How can I pipe standard output and standard error from one command to
another, like csh does with `|&'?
D6) Now that I've converted from ksh to bash, are there equivalents to
ksh features like autoloaded functions and the `whence' command?

Section E: Why does bash do certain things the way it does?

E1) Why is the bash builtin `test' slightly different from /bin/test?
E2) Why does bash sometimes say `Broken pipe'?
E3) When I have terminal escape sequences in my prompt, why does bash
wrap lines at the wrong column?
E4) If I pipe the output of a command into `read variable', why doesn't
the output show up in $variable when the read command finishes?
E5) I have a bunch of shell scripts that use backslash-escaped characters
in arguments to `echo'. Bash doesn't interpret these characters. Why
not, and how can I make it understand them?
E6) Why doesn't a while or for loop get suspended when I type ^Z?
E7) What about empty for loops in Makefiles?
E8) Why does the arithmetic evaluation code complain about `08'?
E9) Why does the pattern matching expression [A-Z]* match files beginning
with every letter except `z'?
E10) Why does `cd //' leave $PWD as `//'?
E11) If I resize my xterm while another program is running, why doesn't bash
notice the change?
E12) Why don't negative offsets in substring expansion work like I expect?

Section F: Things to watch out for on certain Unix versions

F1) Why can't I use command line editing in my `cmdtool'?
F2) I built bash on Solaris 2. Why do globbing expansions and filename
completion chop off the first few characters of each filename?
F3) Why does bash dump core after I interrupt username completion or
`~user' tilde expansion on a machine running NIS?
F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
F5) Why does bash report syntax errors when my C News scripts use a
redirection before a subshell command?
F6) Why can't I use vi-mode editing on Red Hat Linux 6.1?
F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on
HP/UX 11.x?

Section G: How can I get bash to do certain common things?

G1) How can I get bash to read and display eight-bit characters?
G2) How do I write a function `x' to replace builtin command `x', but
still invoke the command from within the function?
G3) How can I find the value of a shell variable whose name is the value
of another shell variable?
G4) How can I make the bash `time' reserved word print timing output that
looks like the output from my system's /usr/bin/time?
G5) How do I get the current directory into my prompt?
G6) How can I rename "*.foo" to "*.bar"?
G7) How can I translate a filename from uppercase to lowercase?
G8) How can I write a filename expansion (globbing) pattern that will match
all files in the current directory except "." and ".."?

Section H: Where do I go from here?

H1) How do I report bugs in bash, and where should I look for fixes and
advice?
H2) What kind of bash documentation is there?
H3) What's coming in future versions?
H4) What's on the bash `wish list'?
H5) When will the next release appear?

----------
Section A: The Basics

A1) What is it?

Bash is a Unix command interpreter (shell). It is an implementation of
the Posix 1003.2 shell standard, and resembles the Korn and System V
shells.

Bash contains a number of enhancements over those shells, both
for interactive use and shell programming. Features geared
toward interactive use include command line editing, command
history, job control, aliases, and prompt expansion. Programming
features include additional variable expansions, shell
arithmetic, and a number of variables and options to control
shell behavior.

Bash was originally written by Brian Fox of the Free Software
Foundation. The current developer and maintainer is Chet Ramey
of Case Western Reserve University.

A2) What's the latest version?

The latest version is 2.05b, first made available on Wednesday, 17
July, 2002.

A3) Where can I get it?

Bash is the GNU project's shell, and so is available from the
master GNU archive site, ftp.gnu.org, and its mirrors. The
latest version is also available for FTP from ftp.cwru.edu.
The following URLs tell how to get version 2.05b:

ftp://ftp.gnu.org/pub/gnu/bash/bash-2.05b.tar.gz
ftp://ftp.cwru.edu/pub/bash/bash-2.05b.tar.gz

Formatted versions of the documentation are available with the URLs:

ftp://ftp.gnu.org/pub/gnu/bash/bash-doc-2.05b.tar.gz
ftp://ftp.cwru.edu/pub/bash/bash-doc-2.05b.tar.gz

A4) On what machines will bash run?

Bash has been ported to nearly every version of UNIX. All you
should have to do to build it on a machine for which a port
exists is to type `configure' and then `make'. The build process
will attempt to discover the version of UNIX you have and tailor
itself accordingly, using a script created by GNU autoconf.

More information appears in the file `INSTALL' in the distribution.

The Bash web page (http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html)
explains how to obtain binary versions of bash for most of the major
commercial Unix systems.

A5) Will bash run on operating systems other than Unix?

Configuration specifics for Unix-like systems such as QNX and
LynxOS are included in the distribution. Bash-2.05 and later
versions should compile and run on Minix 2.0 (patches were
contributed), but I don't believe anyone has built bash-2.x on
earlier Minix versions yet.

Bash has been ported to versions of Windows implementing the Win32
programming interface. This includes Windows 95 and Windows NT.
The port was done by Cygnus Solutions as part of their CYGWIN
project. For more information about the project, look at the URLs

http://www.cygwin.com/
http://sourceware.cygnus.com/cygwin

Cygnus originally ported bash-1.14.7, and that port was part of their
early GNU-Win32 (the original name) releases. Cygnus has also done a
port of bash-2.05 to the CYGWIN environment, and it is available as
part of their current release.

Bash-2.05b should require no local Cygnus changes to build and run under
CYGWIN.

The Cygnus port works only on Intel machines. There is a port of bash
(I don't know which version) to the alpha/NT environment available from

ftp://ftp.gnustep.org//pub/win32/

DJ Delorie has a port of bash-2.x which runs under MS-DOS, as part
of the DJGPP project. For more information on the project, see

http://www.delorie.com/djgpp/

I have been told that the original DJGPP port was done by Daisuke Aoyama.

Mark Elbrecht has sent me notice that bash-2.04
is available for DJGPP V2. The files are available as:

ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/ binary
ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/ documentation
ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/ source

Mark has begun to work with bash-2.05, but I don't know the status.

Ports of bash-1.12 and bash-2.0 are available for OS/2 from

ftp://hobbes.nmsu.edu/pub/os2/util/shell/bash_112.zip
ftp://hobbes.nmsu.edu/pub/os2/util/shell/bash-2.0(253).zip

I haven't looked at either, but the second appears to be a binary-only
distribution. Beware.

I have received word that Bash (I'm not sure which version, but I
believe that it's at least bash-2.02.1) is the standard shell on
BeOS.

A6) How can I build bash with gcc?

Bash configures to use gcc by default if it is available. Read the
file INSTALL in the distribution for more information.

A7) How can I make bash my login shell?

Some machines let you use `chsh' to change your login shell. Other
systems use `passwd -s' or `passwd -e'. If one of these works for
you, that's all you need. Note that many systems require the full
pathname to a shell to appear in /etc/shells before you can make it
your login shell. For this, you may need the assistance of your
friendly local system administrator.

If you cannot do this, you can still use bash as your login shell, but
you need to perform some tricks. The basic idea is to add a command
to your login shell's startup file to replace your login shell with
bash.

For example, if your login shell is csh or tcsh, and you have installed
bash in /usr/gnu/bin/bash, add the following line to ~/.login:

if ( -f /usr/gnu/bin/bash ) exec /usr/gnu/bin/bash --login

(the `--login' tells bash that it is a login shell).

It's not a good idea to put this command into ~/.cshrc, because every
csh you run without the `-f' option, even ones started to run csh scripts,
reads that file. If you must put the command in ~/.cshrc, use something
like

if ( $?prompt ) exec /usr/gnu/bin/bash --login

to ensure that bash is exec'd only when the csh is interactive.

If your login shell is sh or ksh, you have to do two things.

First, create an empty file in your home directory named `.bash_profile'.
The existence of this file will prevent the exec'd bash from trying to
read ~/.profile, and re-execing itself over and over again. ~/.bash_profile
is the first file bash tries to read initialization commands from when
it is invoked as a login shell.

Next, add a line similar to the above to ~/.profile:

[ -f /usr/gnu/bin/bash ] && [ -x /usr/gnu/bin/bash ] && \
exec /usr/gnu/bin/bash --login

This will cause login shells to replace themselves with bash running as
a login shell. Once you have this working, you can copy your initialization
code from ~/.profile to ~/.bash_profile.

I have received word that the recipe supplied above is insufficient for
machines running CDE. CDE has a maze of twisty little startup files, all
slightly different.

If you cannot change your login shell in the password file to bash, you
will have to (apparently) live with CDE using the shell in the password
file to run its startup scripts. If you have changed your shell to bash,
there is code in the CDE startup files (on Solaris, at least) that attempts
to do the right thing. It is, however, often broken, and may require that
you use the $BASH_ENV trick described below.

`dtterm' claims to use $SHELL as the default program to start, so if you
can change $SHELL in the CDE startup files, you should be able to use bash
in your terminal windows.

Setting DTSOURCEPROFILE in ~/.dtprofile will cause the `Xsession' program
to read your login shell's startup files. You may be able to use bash for
the rest of the CDE programs by setting SHELL to bash in ~/.dtprofile as
well, but I have not tried this.

You can use the above `exec' recipe to start bash when not logging in with
CDE by testing the value of the DT variable:

if [ -n "$DT" ]; then
[ -f /usr/gnu/bin/bash ] && exec /usr/gnu/bin/bash --login
fi

If CDE starts its shells non-interactively during login, the login shell
startup files (~/.profile, ~/.bash_profile) will not be sourced at login.
To get around this problem, append a line similar to the following to your
~/.dtprofile:

BASH_ENV=${HOME}/.bash_profile ; export BASH_ENV

and add the following line to the beginning of ~/.bash_profile:

unset BASH_ENV

A8) I just changed my login shell to bash, and now I can't FTP into my
machine. Why not?

You must add the full pathname to bash to the file /etc/shells. As
noted in the answer to the previous question, many systems require
this before you can make bash your login shell.

Most versions of ftpd use this file to prohibit `special' users
such as `uucp' and `news' from using FTP.

A9) What's the `POSIX Shell and Utilities standard'?

POSIX is a name originally coined by Richard Stallman for a
family of open system standards based on UNIX. There are a
number of aspects of UNIX under consideration for
standardization, from the basic system services at the system
call and C library level to applications and tools to system
administration and management. Each area of standardization is
assigned to a working group in the 1003 series.

The POSIX Shell and Utilities standard was originally developed by
IEEE Working Group 1003.2 (POSIX.2). Today it has been merged with
the original 1003.1 Working Group and is maintained by the Austin
Group (a joint working group of the IEEE, The Open Group and
ISO/IEC SC22/WG15). Today the Shell and Utilities are a volume
within the set of documents that make up IEEE Std 1003.1-2001, and
thus now the former POSIX.2 (from 1992) is now part of the current
POSIX.1 standard (POSIX 1003.1-2001).

The Shell and Utilities volume concentrates on the command
interpreter interface and utility programs commonly executed from
the command line or by other programs. The standard is freely
available on the web at http://www.UNIX-systems.org/version3/ .
Work continues at the Austin Group on maintenance issues; see
http://www.opengroup.org/austin/ to join the discussions.

Bash is concerned with the aspects of the shell's behavior defined
by the POSIX Shell and Utilities volume. The shell command
language has of course been standardized, including the basic flow
control and program execution constructs, I/O redirection and
pipelining, argument handling, variable expansion, and quoting.

The `special' builtins, which must be implemented as part of the
shell to provide the desired functionality, are specified as
being part of the shell; examples of these are `eval' and
`export'. Other utilities appear in the sections of POSIX not
devoted to the shell which are commonly (and in some cases must
be) implemented as builtin commands, such as `read' and `test'.
POSIX also specifies aspects of the shell's interactive
behavior as part of the UPE, including job control and command
line editing. Only vi-style line editing commands have been
standardized; emacs editing commands were left out due to
objections.

The latest version of the POSIX Shell and Utilities standard is
available (now updated to the 2003 Edition incorporating the
Technical Corrigendum 1), as part of the Single UNIX Specification
Version 3 at

http://www.UNIX-systems.org/version3/

A10) What is the bash `posix mode'?

Although bash is an implementation of the POSIX shell
specification, there are areas where the bash default behavior
differs from that spec. The bash `posix mode' changes the bash
behavior in these areas so that it obeys the spec more closely.

Posix mode is entered by starting bash with the --posix or
'-o posix' option or executing `set -o posix' after bash is running.

The specific aspects of bash which change when posix mode is
active are listed in the file POSIX in the bash distribution.
They are also listed in a section in the Bash Reference Manual
(from which that file is generated).

Section B: The latest version

B1) What's new in version 2.05b?

The raison d'etre for bash-2.05b is to make a second intermediate
release containing the first of the new features to be available
in bash-3.0 and get feedback on those features before proceeding.
The major new feature is multibyte character support in both Bash
and Readline.

Bash-2.05b contains the following new features (see the manual page for
complete descriptions and the CHANGES and NEWS files in the bash-2.05b
distribution):

o support for multibyte characters has been added to both bash and readline

o the DEBUG trap is now run *before* simple commands, ((...)) commands,
[[...]] conditional commands, and for ((...)) loops

o the shell now performs arithmetic in the largest integer size the machine
supports (intmax_t)

o there is a new \D{...} prompt expansion; passes the `...' to strftime(3)
and inserts the result into the expanded prompt

o there is a new `here-string' redirection operator: <<< word

o when displaying variables, function attributes and definitions are shown
separately, allowing them to be re-used as input (attempting to re-use
the old output would result in syntax errors).

o `read' has a new `-u fd' option to read from a specified file descriptor

o the bash debugger in examples/bashdb has been modified to work with the
new DEBUG trap semantics, the command set has been made more gdb-like,
and the changes to $LINENO make debugging functions work better

o the expansion of $LINENO inside a shell function is only relative to the
function start if the shell is interactive -- if the shell is running a
script, $LINENO expands to the line number in the script. This is as
POSIX-2001 requires

A short feature history dating from Bash-2.0:

Bash-2.05a introduced the following new features:

o The `printf' builtin has undergone major work

o There is a new read-only `shopt' option: login_shell, which is set by
login shells and unset otherwise

o New `\A' prompt string escape sequence; expanding to time in 24-hour
HH:MM format

o New `-A group/-g' option to complete and compgen; goes group name
completion

o New [+-]O invocation option to set and unset `shopt' options at startup

o ksh-like `ERR' trap

o `for' loops now allow empty word lists after the `in' reserved word

o new `hard' and `soft' arguments for the `ulimit' builtin

o Readline can be configured to place the user at the same point on the line
when retrieving commands from the history list

o Readline can be configured to skip `hidden' files (filenames with a leading
`.' on Unix) when performing completion

Bash-2.05 introduced the following new features:

o This version has once again reverted to using locales and strcoll(3) when
processing pattern matching bracket expressions, as POSIX requires.
o Added a new `--init-file' invocation argument as a synonym for `--rcfile',
per the new GNU coding standards.
o The /dev/tcp and /dev/udp redirections now accept service names as well as
port numbers.
o `complete' and `compgen' now take a `-o value' option, which controls some
of the aspects of that compspec. Valid values are:

default - perform bash default completion if programmable
completion produces no matches
dirnames - perform directory name completion if programmable
completion produces no matches
filenames - tell readline that the compspec produces filenames,
so it can do things like append slashes to
directory names and suppress trailing spaces
o A new loadable builtin, realpath, which canonicalizes and expands symlinks
in pathname arguments.
o When `set' is called without options, it prints function defintions in a
way that allows them to be reused as input. This affects `declare' and
`declare -p' as well. This only happens when the shell is not in POSIX
mode, since POSIX.2 forbids this behavior.

Bash-2.04 introduced the following new features:

o Programmable word completion with the new `complete' and `compgen' builtins;
examples are provided in examples/complete/complete-examples
o `history' has a new `-d' option to delete a history entry
o `bind' has a new `-x' option to bind key sequences to shell commands
o The prompt expansion code has new `\j' and `\l' escape sequences
o The `no_empty_cmd_completion' shell option, if enabled, inhibits
command completion when TAB is typed on an empty line
o `help' has a new `-s' option to print a usage synopsis
o New arithmetic operators: var++, var--, ++var, --var, expr1,expr2 (comma)
o New ksh93-style arithmetic for command:
for ((expr1 ; expr2; expr3 )); do list; done
o `read' has new options: `-t', `-n', `-d', `-s'
o The redirection code handles several filenames specially: /dev/fd/N,
/dev/stdin, /dev/stdout, /dev/stderr
o The redirection code now recognizes /dev/tcp/HOST/PORT and
/dev/udp/HOST/PORT and tries to open a TCP or UDP socket, respectively,
to the specified port on the specified host
o The ${!prefix*} expansion has been implemented
o A new FUNCNAME variable, which expands to the name of a currently-executing
function
o The GROUPS variable is no longer readonly
o A new shopt `xpg_echo' variable, to control the behavior of echo with
respect to backslash-escape sequences at runtime
o The NON_INTERACTIVE_LOGIN_SHELLS #define has returned

The version of Readline released with Bash-2.04, Readline-4.1, had several
new features as well:

o Parentheses matching is always compiled into readline, and controllable
with the new `blink-matching-paren' variable
o The history-search-forward and history-search-backward functions now leave
point at the end of the line when the search string is empty, like
reverse-search-history, and forward-search-history
o A new function for applications: rl_on_new_line_with_prompt()
o New variables for applications: rl_already_prompted, and rl_gnu_readline_p

Bash-2.03 had very few new features, in keeping with the convention
that odd-numbered releases provide mainly bug fixes. A number of new
features were added to Readline, mostly at the request of the Cygnus
folks.

A new shopt option, `restricted_shell', so that startup files can test
whether or not the shell was started in restricted mode
Filename generation is now performed on the words between ( and ) in
compound array assignments (this is really a bug fix)
OLDPWD is now auto-exported, as POSIX.2 requires
ENV and BASH_ENV are read-only variables in a restricted shell
Bash may now be linked against an already-installed Readline library,
as long as the Readline library is version 4 or newer
All shells begun with the `--login' option will source the login shell
startup files, even if the shell is not interactive

There were lots of changes to the version of the Readline library released
along with Bash-2.03. For a complete list of the changes, read the file
CHANGES in the Bash-2.03 distribution.

Bash-2.02 contained the following new features:

a new version of malloc (based on the old GNU malloc code in previous
bash versions) that is more page-oriented, more conservative
with memory usage, does not `orphan' large blocks when they
are freed, is usable on 64-bit machines, and has allocation
checking turned on unconditionally
POSIX.2-style globbing character classes ([:alpha:], [:alnum:], etc.)
POSIX.2-style globbing equivalence classes
POSIX.2-style globbing collating symbols
the ksh [[...]] extended conditional command
the ksh egrep-style extended pattern matching operators
a new `printf' builtin
the ksh-like $( $(cat filename)
new tilde prefixes that expand to directories from the directory stack
new `**' arithmetic operator to do exponentiation
case-insensitive globbing (filename expansion)
menu completion a la tcsh
`magic-space' history expansion function like tcsh
the readline inputrc `language' has a new file inclusion directive ($include)

Bash-2.01 contained only a few new features:

new `GROUPS' builtin array variable containing the user's group list
new bindable readline commands: history-and-alias-expand-line and
alias-expand-line

Bash-2.0 contained extensive changes and new features from bash-1.14.7.
Here's a short list:

new `time' reserved word to time pipelines, shell builtins, and
shell functions
one-dimensional arrays with a new compound assignment statement,
appropriate expansion constructs and modifications to some
of the builtins (read, declare, etc.) to use them
new quoting syntaxes for ANSI-C string expansion and locale-specific
string translation
new expansions to do substring extraction, pattern replacement, and
indirect variable expansion
new builtins: `disown' and `shopt'
new variables: HISTIGNORE, SHELLOPTS, PIPESTATUS, DIRSTACK, GLOBIGNORE,
MACHTYPE, BASH_VERSINFO
special handling of many unused or redundant variables removed
(e.g., $notify, $glob_dot_filenames, $no_exit_on_failed_exec)
dynamic loading of new builtin commands; many loadable examples provided
new prompt expansions: \a, \e, \n, \H, \T, \@, \v, \V
history and aliases available in shell scripts
new readline variables: enable-keypad, mark-directories, input-meta,
visible-stats, disable-completion, comment-begin
new readline commands to manipulate the mark and operate on the region
new readline emacs mode commands and bindings for ksh-88 compatibility
updated and extended builtins
new DEBUG trap
expanded (and now documented) restricted shell mode

implementation stuff:
autoconf-based configuration
nearly all of the bugs reported since version 1.14 have been fixed
most builtins converted to use builtin `getopt' for consistency
most builtins use -p option to display output in a reusable form
(for consistency)
grammar tighter and smaller (66 reduce-reduce conflicts gone)
lots of code now smaller and faster
test suite greatly expanded

B2) Are there any user-visible incompatibilities between bash-2.05b and
bash-1.14.7?

There are a few incompatibilities between version 1.14.7 and version 2.05b.
They are detailed in the file COMPAT in the bash distribution. That file
is not meant to be all-encompassing; send mail to bash-maintainers@gnu.org
if if you find something that's not mentioned there.

Section C: Differences from other Unix shells

C1) How does bash differ from sh, the Bourne shell?

This is a non-comprehensive list of features that differentiate bash
from the SVR4.2 shell. The bash manual page explains these more
completely.

Things bash has that sh does not:
long invocation options
[+-]O invocation option
-l invocation option
`!' reserved word to invert pipeline return value
`time' reserved word to time pipelines and shell builtins
the `function' reserved word
the `select' compound command and reserved word
arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
new $'...' and $"..." quoting
the $(...) form of command substitution
the $( $(cat filename)
the ${#param} parameter value length operator
the ${!param} indirect parameter expansion operator
the ${!param*} prefix expansion operator
the ${param:offset[:length]} parameter substring operator
the ${param/pat[/string]} parameter pattern substitution operator
expansions to perform substring removal (${p%[%]w}, ${p#[#]w})
expansion of positional parameters beyond $9 with ${num}
variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, REPLY,
TIMEFORMAT, PPID, PWD, OLDPWD, SHLVL, RANDOM, SECONDS,
LINENO, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE, HOSTNAME,
ENV, PS3, PS4, DIRSTACK, PIPESTATUS, HISTSIZE, HISTFILE,
HISTFILESIZE, HISTCONTROL, HISTIGNORE, GLOBIGNORE, GROUPS,
PROMPT_COMMAND, FCEDIT, FIGNORE, IGNOREEOF, INPUTRC,
SHELLOPTS, OPTERR, HOSTFILE, TMOUT, FUNCNAME, histchars,
auto_resume
DEBUG trap
ERR trap
variable arrays with new compound assignment syntax
redirections: <>, &>, >|, <<<, [n]<&word-, [n]>&word-
prompt string special char translation and variable expansion
auto-export of variables in initial environment
command search finds functions before builtins
bash return builtin will exit a file sourced with `.'
builtins: cd -/-L/-P, exec -l/-c/-a, echo -e/-E, hash -d/-l/-p/-t.
export -n/-f/-p/name=value, pwd -L/-P,
read -e/-p/-a/-t/-n/-d/-s/-u,
readonly -a/-f/name=value, trap -l, set +o,
set -b/-m/-o option/-h/-p/-B/-C/-H/-P,
unset -f/-v, ulimit -m/-p/-u,
type -a/-p/-t/-f/-P, suspend -f, kill -n,
test -o optname/s1 == s2/s1 < s2/s1 > s2/-nt/-ot/-ef/-O/-G/-S
bash reads ~/.bashrc for interactive shells, $ENV for non-interactive
bash restricted shell mode is more extensive
bash allows functions and variables with the same name
brace expansion
tilde expansion
arithmetic expansion with $((...)) and `let' builtin
the `[[...]]' extended conditional command
process substitution
aliases and alias/unalias builtins
local variables in functions and `local' builtin
readline and command-line editing with programmable completion
command history and history/fc builtins
csh-like history expansion
other new bash builtins: bind, command, compgen, complete, builtin,
declare/typeset, dirs, enable, fc, help,
history, logout, popd, pushd, disown, shopt,
printf
exported functions
filename generation when using output redirection (command >a*)
POSIX.2-style globbing character classes
POSIX.2-style globbing equivalence classes
POSIX.2-style globbing collating symbols
egrep-like extended pattern matching operators
case-insensitive pattern matching and globbing
variable assignments preceding commands affect only that command,
even for builtins and functions
posix mode
redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr,
/dev/tcp/host/port, /dev/udp/host/port

Things sh has that bash does not:
uses variable SHACCT to do shell accounting
includes `stop' builtin (bash can use alias stop='kill -s STOP')
`newgrp' builtin
turns on job control if called as `jsh'
$TIMEOUT (like bash $TMOUT)
`^' is a synonym for `|'
new SVR4.2 sh builtins: mldmode, priv

Implementation differences:
redirection to/from compound commands causes sh to create a subshell
bash does not allow unbalanced quotes; sh silently inserts them at EOF
bash does not mess with signal 11
sh sets (euid, egid) to (uid, gid) if -p not supplied and uid < 100
bash splits only the results of expansions on IFS, using POSIX.2
field splitting rules; sh splits all words on IFS
sh does not allow MAILCHECK to be unset (?)
sh does not allow traps on SIGALRM or SIGCHLD
bash allows multiple option arguments when invoked (e.g. -x -v);
sh allows only a single option argument (`sh -x -v' attempts
to open a file named `-v', and, on SunOS 4.1.4, dumps core.
On Solaris 2.4 and earlier versions, sh goes into an infinite
loop.)
sh exits a script if any builtin fails; bash exits only if one of
the POSIX.2 `special' builtins fails

C2) How does bash differ from the Korn shell, version ksh88?

Things bash has or uses that ksh88 does not:
long invocation options
[-+]O invocation option
-l invocation option
`!' reserved word
arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
arithmetic in largest machine-supported size (intmax_t)
posix mode and posix conformance
command hashing
tilde expansion for assignment statements that look like $PATH
process substitution with named pipes if /dev/fd is not available
the ${!param} indirect parameter expansion operator
the ${!param*} prefix expansion operator
the ${param:offset[:length]} parameter substring operator
the ${param/pat[/string]} parameter pattern substitution operator
variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, SHLVL,
TIMEFORMAT, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE,
HISTFILESIZE, HISTIGNORE, HISTCONTROL, PROMPT_COMMAND,
IGNOREEOF, FIGNORE, INPUTRC, HOSTFILE, DIRSTACK,
PIPESTATUS, HOSTNAME, OPTERR, SHELLOPTS, GLOBIGNORE,
GROUPS, FUNCNAME, histchars, auto_resume
prompt expansion with backslash escapes and command substitution
redirection: &> (stdout and stderr), <<<, [n]<&word-, [n]>&word-
more extensive and extensible editing and programmable completion
builtins: bind, builtin, command, declare, dirs, echo -e/-E, enable,
exec -l/-c/-a, fc -s, export -n/-f/-p, hash, help, history,
jobs -x/-r/-s, kill -s/-n/-l, local, logout, popd, pushd,
read -e/-p/-a/-t/-n/-d/-s, readonly -a/-n/-f/-p,
set -o braceexpand/-o histexpand/-o interactive-comments/
-o notify/-o physical/-o posix/-o hashall/-o onecmd/
-h/-B/-C/-b/-H/-P, set +o, suspend, trap -l, type,
typeset -a/-F/-p, ulimit -u, umask -S, alias -p, shopt,
disown, printf, complete, compgen
`!' csh-style history expansion
POSIX.2-style globbing character classes
POSIX.2-style globbing equivalence classes
POSIX.2-style globbing collating symbols
egrep-like extended pattern matching operators
case-insensitive pattern matching and globbing
`**' arithmetic operator to do exponentiation
redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr
arrays of unlimited size
TMOUT is default timeout for `read' and `select'

Things ksh88 has or uses that bash does not:
tracked aliases (alias -t)
variables: ERRNO, FPATH, EDITOR, VISUAL
co-processes (|&, >&p, <&p)
weirdly-scoped functions
typeset +f to list all function names without definitions
text of command history kept in a file, not memory
builtins: alias -x, cd old new, fc -e -, newgrp, print,
read -p/-s/var?prompt, set -A/-o gmacs/
-o bgnice/-o markdirs/-o nolog/-o trackall/-o viraw/-s,
typeset -H/-L/-R/-Z/-A/-ft/-fu/-fx/-l/-u/-t, whence
using environment to pass attributes of exported variables
arithmetic evaluation done on arguments to some builtins
reads .profile from $PWD when invoked as login shell

Implementation differences:
ksh runs last command of a pipeline in parent shell context
bash has brace expansion by default (ksh88 compile-time option)
bash has fixed startup file for all interactive shells; ksh reads $ENV
bash has exported functions
bash command search finds functions before builtins
bash waits for all commands in pipeline to exit before returning status
emacs-mode editing has some slightly different key bindings

C3) Which new features in ksh-93 are not in bash, and which are?

New things in ksh-93 not in bash-2.05b:
associative arrays
floating point arithmetic and variables
math library functions
${!name[sub]} name of subscript for associative array
`.' is allowed in variable names to create a hierarchical namespace
more extensive compound assignment syntax
discipline functions
`sleep' and `getconf' builtins (bash has loadable versions)
typeset -n and `nameref' variables
KEYBD trap
variables: .sh.edchar, .sh.edmode, .sh.edcol, .sh.edtext, .sh.version,
.sh.name, .sh.subscript, .sh.value, .sh.match, HISTEDIT
backreferences in pattern matching (\N)
`&' operator in pattern lists for matching
print -f (bash uses printf)
`fc' has been renamed to `hist'
`.' can execute shell functions
exit statuses between 0 and 255
set -o pipefail
`+=' variable assignment operator
FPATH and PATH mixing
getopts -a
-I invocation option
DEBUG trap now executed before each simple command, instead of after
printf %H, %P, %T, %Z modifiers, output base for %d
lexical scoping for local variables in `ksh' functions
no scoping for local variables in `POSIX' functions

New things in ksh-93 present in bash-2.05b:
[n]<&word- and [n]>&word- redirections (combination dup and close)
for (( expr1; expr2; expr3 )) ; do list; done - arithmetic for command
?:, ++, --, `expr1 , expr2' arithmetic operators
expansions: ${!param}, ${param:offset[:len]}, ${param/pat[/str]},
${!param*}
compound array assignment
the `!' reserved word
loadable builtins -- but ksh uses `builtin' while bash uses `enable'
`command', `builtin', `disown' builtins
new $'...' and $"..." quoting
FIGNORE (but bash uses GLOBIGNORE), HISTCMD
set -o notify/-C
changes to kill builtin
read -A (bash uses read -a)
read -t/-d
trap -p
exec -c/-a
`.' restores the positional parameters when it completes
POSIX.2 `test'
umask -S
unalias -a
command and arithmetic substitution performed on PS1, PS4, and ENV
command name completion
ENV processed only for interactive shells

Section D: Why does bash do some things differently than other Unix shells?

D1) Why does bash run a different version of `command' than
`which command' says it will?

On many systems, `which' is actually a csh script that assumes
you're running csh. In tcsh, `which' and its cousin `where'
are builtins. On other Unix systems, `which' is a perl script
that uses the PATH environment variable.

The csh script version reads the csh startup files from your
home directory and uses those to determine which `command' will
be invoked. Since bash doesn't use any of those startup files,
there's a good chance that your bash environment differs from
your csh environment. The bash `type' builtin does everything
`which' does, and will report correct results for the running
shell. If you're really wedded to the name `which', try adding
the following function definition to your .bashrc:

which()
{
builtin type "$@"
}

If you're moving from tcsh and would like to bring `where' along
as well, use this function:

where()
{
builtin type -a "$@"
}

D2) Why doesn't bash treat brace expansions exactly like csh?

The only difference between bash and csh brace expansion is that
bash requires a brace expression to contain at least one unquoted
comma if it is to be expanded. Any brace-surrounded word not
containing an unquoted comma is left unchanged by the brace
expansion code. This affords the greatest degree of sh
compatibility.

Bash, ksh, zsh, and pd-ksh all implement brace expansion this way.

D3) Why doesn't bash have csh variable modifiers?

Posix has specified a more powerful, albeit somewhat more cryptic,
mechanism cribbed from ksh, and bash implements it.

${parameter%word}
Remove smallest suffix pattern. The WORD is expanded to produce
a pattern. It then expands to the value of PARAMETER, with the
smallest portion of the suffix matched by the pattern deleted.

x=file.c
echo ${x%.c}.o
-->file.o

${parameter%%word}

Remove largest suffix pattern. The WORD is expanded to produce
a pattern. It then expands to the value of PARAMETER, with the
largest portion of the suffix matched by the pattern deleted.

x=posix/src/std
echo ${x%%/*}
-->posix

${parameter#word}
Remove smallest prefix pattern. The WORD is expanded to produce
a pattern. It then expands to the value of PARAMETER, with the
smallest portion of the prefix matched by the pattern deleted.

x=$HOME/src/cmd
echo ${x#$HOME}
-->/src/cmd

${parameter##word}
Remove largest prefix pattern. The WORD is expanded to produce
a pattern. It then expands to the value of PARAMETER, with the
largest portion of the prefix matched by the pattern deleted.

x=/one/two/three
echo ${x##*/}
-->three

Given
a=/a/b/c/d
b=b.xxx

csh bash result
--- ---- ------
$a:h ${a%/*} /a/b/c
$a:t ${a##*/} d
$b:r ${b%.*} b
$b:e ${b##*.} xxx

D4) How can I make my csh aliases work when I convert to bash?

Bash uses a different syntax to support aliases than csh does.
The details can be found in the documentation. We have provided
a shell script which does most of the work of conversion for you;
this script can be found in ./examples/misc/aliasconv.sh. Here is
how you use it:

Start csh in the normal way for you. (e.g., `csh')

Pipe the output of `alias' through `aliasconv.sh', saving the
results into `bash_aliases':

alias | bash aliasconv.sh >bash_aliases

Edit `bash_aliases', carefully reading through any created
functions. You will need to change the names of some csh specific
variables to the bash equivalents. The script converts $cwd to
$PWD, $term to $TERM, $home to $HOME, $user to $USER, and $prompt
to $PS1. You may also have to add quotes to avoid unwanted
expansion.

For example, the csh alias:

alias cd 'cd \!*; echo $cwd'

is converted to the bash function:

cd () { command cd "$@"; echo $PWD ; }

The only thing that needs to be done is to quote $PWD:

cd () { command cd "$@"; echo "$PWD" ; }

Merge the edited file into your ~/.bashrc.

There is an additional, more ambitious, script in
examples/misc/cshtobash that attempts to convert your entire csh
environment to its bash equivalent. This script can be run as
simply `cshtobash' to convert your normal interactive
environment, or as `cshtobash ~/.login' to convert your login
environment.

D5) How can I pipe standard output and standard error from one command to
another, like csh does with `|&'?

Use
command 2>&1 | command2

The key is to remember that piping is performed before redirection, so
file descriptor 1 points to the pipe when it is duplicated onto file
descriptor 2.

D6) Now that I've converted from ksh to bash, are there equivalents to
ksh features like autoloaded functions and the `whence' command?

There are features in ksh-88 and ksh-93 that do not have direct bash
equivalents. Most, however, can be emulated with very little trouble.

ksh-88 feature Bash equivalent
-------------- ---------------
compiled-in aliases set up aliases in .bashrc; some ksh aliases are
bash builtins (hash, history, type)
coprocesses named pipe pairs (one for read, one for write)
typeset +f declare -F
cd, print, whence function substitutes in examples/functions/kshenv
autoloaded functions examples/functions/autoload is the same as typeset -fu
read var?prompt read -p prompt var

ksh-93 feature Bash equivalent
-------------- ---------------
sleep, getconf Bash has loadable versions in examples/loadables
${.sh.version} $BASH_VERSION
print -f printf
hist alias hist=fc
$HISTEDIT $FCEDIT

Section E: How can I get bash to do certain things, and why does bash do
things the way it does?

E1) Why is the bash builtin `test' slightly different from /bin/test?

The specific example used here is [ ! x -o x ], which is false.

Bash's builtin `test' implements the Posix.2 spec, which can be
summarized as follows (the wording is due to David Korn):

Here is the set of rules for processing test arguments.

0 Args: False
1 Arg: True iff argument is not null.
2 Args: If first arg is !, True iff second argument is null.
If first argument is unary, then true if unary test is true
Otherwise error.
3 Args: If second argument is a binary operator, do binary test of $1 $3
If first argument is !, negate two argument test of $2 $3
If first argument is `(' and third argument is `)', do the
one-argument test of the second argument.
Otherwise error.
4 Args: If first argument is !, negate three argument test of $2 $3 $4.
Otherwise unspecified
5 or more Args: unspecified. (Historical shells would use their
current algorithm).

The operators -a and -o are considered binary operators for the purpose
of the 3 Arg case.

As you can see, the test becomes (not (x or x)), which is false.

E2) Why does bash sometimes say `Broken pipe'?

If a sequence of commands appears in a pipeline, and one of the
reading commands finishes before the writer has finished, the
writer receives a SIGPIPE signal. Many other shells special-case
SIGPIPE as an exit status in the pipeline and do not report it.
For example, in:

ps -aux | head

`head' can finish before `ps' writes all of its output, and ps
will try to write on a pipe without a reader. In that case, bash
will print `Broken pipe' to stderr when ps is killed by a
SIGPIPE.

You can build a version of bash that will not report SIGPIPE errors
by uncommenting the definition of DONT_REPORT_SIGPIPE in the file
config-top.h.

E3) When I have terminal escape sequences in my prompt, why does bash
wrap lines at the wrong column?

Readline, the line editing library that bash uses, does not know
that the terminal escape sequences do not take up space on the
screen. The redisplay code assumes, unless told otherwise, that
each character in the prompt is a `printable' character that
takes up one character position on the screen.

You can use the bash prompt expansion facility (see the PROMPTING
section in the manual page) to tell readline that sequences of
characters in the prompt strings take up no screen space.

Use the \[ escape to begin a sequence of non-printing characters,
and the \] escape to signal the end of such a sequence.

E4) If I pipe the output of a command into `read variable', why doesn't
the output show up in $variable when the read command finishes?

This has to do with the parent-child relationship between Unix
processes. It affects all commands run in pipelines, not just
simple calls to `read'. For example, piping a command's output
into a `while' loop that repeatedly calls `read' will result in
the same behavior.

Each element of a pipeline runs in a separate process, a child of
the shell running the pipeline. A subprocess cannot affect its
parent's environment. When the `read' command sets the variable
to the input, that variable is set only in the subshell, not the
parent shell. When the subshell exits, the value of the variable
is lost.

Many pipelines that end with `read variable' can be converted
into command substitutions, which will capture the output of
a specified command. The output can then be assigned to a
variable:

grep ^gnu /usr/lib/news/active | wc -l | read ngroup

can be converted into

ngroup=$(grep ^gnu /usr/lib/news/active | wc -l)

This does not, unfortunately, work to split the text among
multiple variables, as read does when given multiple variable
arguments. If you need to do this, you can either use the
command substitution above to read the output into a variable
and chop up the variable using the bash pattern removal
expansion operators or use some variant of the following
approach.

Say /usr/local/bin/ipaddr is the following shell script:

#! /bin/sh
host `hostname` | awk '/address/ {print $NF}'

Instead of using

/usr/local/bin/ipaddr | read A B C D

to break the local machine's IP address into separate octets, use

OIFS="$IFS"
IFS=.
set -- $(/usr/local/bin/ipaddr)
IFS="$OIFS"
A="$1" B="$2" C="$3" D="$4"

Beware, however, that this will change the shell's positional
parameters. If you need them, you should save them before doing
this.

This is the general approach -- in most cases you will not need to
set $IFS to a different value.

Some other user-supplied alternatives include:

read A B C D << HERE
$(IFS=.; echo $(/usr/local/bin/ipaddr))
HERE

and, where process substitution is available,

read A B C D < <(IFS=.; echo $(/usr/local/bin/ipaddr))

E5) I have a bunch of shell scripts that use backslash-escaped characters
in arguments to `echo'. Bash doesn't interpret these characters. Why
not, and how can I make it understand them?

This is the behavior of echo on most Unix System V machines.

The bash builtin `echo' is modeled after the 9th Edition
Research Unix version of `echo'. It does not interpret
backslash-escaped characters in its argument strings by default;
it requires the use of the -e option to enable the
interpretation. The System V echo provides no way to disable the
special characters; the bash echo has a -E option to disable
them.

There is a configuration option that will make bash behave like
the System V echo and interpret things like `\t' by default. Run
configure with the --enable-xpg-echo-default option to turn this
on. Be aware that this will cause some of the tests run when you
type `make tests' to fail.

There is a shell option, `xpg_echo', settable with `shopt', that will
change the behavior of echo at runtime. Enabling this option turns
on expansion of backslash-escape sequences.

E6) Why doesn't a while or for loop get suspended when I type ^Z?

This is a consequence of how job control works on Unix. The only
thing that can be suspended is the process group. This is a single
command or pipeline of commands that the shell forks and executes.

When you run a while or for loop, the only thing that the shell forks
and executes are any commands in the while loop test and commands in
the loop bodies. These, therefore, are the only things that can be
suspended when you type ^Z.

If you want to be able to stop the entire loop, you need to put it
within parentheses, which will force the loop into a subshell that
may be stopped (and subsequently restarted) as a single unit.

E7) What about empty for loops in Makefiles?

It's fairly common to see constructs like this in automatically-generated
Makefiles:

SUBDIRS = @SUBDIRS@

...

subdirs-clean:
for d in ${SUBDIRS}; do \
( cd $$d && ${MAKE} ${MFLAGS} clean ) \
done

When SUBDIRS is empty, this results in a command like this being passed to
bash:

for d in ; do
( cd $d && ${MAKE} ${MFLAGS} clean )
done

In versions of bash before bash-2.05a, this was a syntax error. If the
reserved word `in' was present, a word must follow it before the semicolon
or newline. The language in the manual page referring to the list of words
being empty referred to the list after it is expanded. These versions of
bash required that there be at least one word following the `in' when the
construct was parsed.

The idiomatic Makefile solution is something like:

SUBDIRS = @SUBDIRS@

subdirs-clean:
subdirs=$SUBDIRS ; for d in $$subdirs; do \
( cd $$d && ${MAKE} ${MFLAGS} clean ) \
done

The latest drafts of the updated POSIX standard have changed this: the
word list is no longer required. Bash versions 2.05a and later accept
the new syntax.

E8) Why does the arithmetic evaluation code complain about `08'?

The bash arithmetic evaluation code (used for `let', $(()), (()), and in
other places), interprets a leading `0' in numeric constants as denoting
an octal number, and a leading `0x' as denoting hexadecimal. This is
in accordance with the POSIX.2 spec, section 2.9.2.1, which states that
arithmetic constants should be handled as signed long integers as defined
by the ANSI/ISO C standard.

The POSIX.2 interpretation committee has confirmed this:

http://www.pasc.org/interps/unofficial/db/p1003.2/pasc-1003.2-173.html

E9) Why does the pattern matching expression [A-Z]* match files beginning
with every letter except `z'?

Bash-2.03, Bash-2.05 and later versions honor the current locale setting
when processing ranges within pattern matching bracket expressions ([A-Z]).
This is what POSIX.2 and SUSv3/XPG6 specify.

The behavior of the matcher in bash-2.05 and later versions depends on the
current LC_COLLATE setting. Setting this variable to `C' or `POSIX' will
result in the traditional behavior ([A-Z] matches all uppercase ASCII
characters). Many other locales, including the en_US locale (the default
on many US versions of Linux) collate the upper and lower case letters like
this:

AaBb...Zz

which means that [A-Z] matches every letter except `z'. Others collate like

aAbBcC...zZ

which means that [A-Z] matches every letter except `a'.

The portable way to specify upper case letters is [:upper:] instead of
A-Z; lower case may be specified as [:lower:] instead of a-z.

Look at the manual pages for setlocale(3), strcoll(3), and, if it is
present, locale(1). If you have locale(1), you can use it to find
your current locale information even if you do not have any of the
LC_ variables set.

My advice is to put

export LC_COLLATE=C

into /etc/profile and inspect any shell scripts run from cron for
constructs like [A-Z]. This will prevent things like

rm [A-Z]*

from removing every file in the current directory except those beginning
with `z' and still allow individual users to change the collation order.
Users may put the above command into their own profiles as well, of course.

E10) Why does `cd //' leave $PWD as `//'?

POSIX.2, in its description of `cd', says that *three* or more leading
slashes may be replaced with a single slash when canonicalizing the
current working directory.

This is, I presume, for historical compatibility. Certain versions of
Unix, and early network file systems, used paths of the form
//hostname/path to access `path' on server `hostname'.

E11) If I resize my xterm while another program is running, why doesn't bash
notice the change?

This is another issue that deals with job control.

The kernel maintains a notion of a current terminal process group. Members
of this process group (processes whose process group ID is equal to the
current terminal process group ID) receive terminal-generated signals like
SIGWINCH. (For more details, see the JOB CONTROL section of the bash
man page.)

If a terminal is resized, the kernel sends SIGWINCH to each member of
the terminal's current process group (the `foreground' process group).

When bash is running with job control enabled, each pipeline (which may be
a single command) is run in its own process group, different from bash's
process group. This foreground process group receives the SIGWINCH; bash
does not. Bash has no way of knowing that the terminal has been resized.

There is a `checkwinsize' option, settable with the `shopt' builtin, that
will cause bash to check the window size and adjust its idea of the
terminal's dimensions each time a process stops or exits and returns control
of the terminal to bash. Enable it with `shopt -s checkwinsize'.

E12) Why don't negative offsets in substring expansion work like I expect?

When substring expansion of the form ${param:offset[:length} is used,
an `offset' that evaluates to a number less than zero counts back from
the end of the expanded value of $param.

When a negative `offset' begins with a minus sign, however, unexpected things
can happen. Consider

a=12345678
echo ${a:-4}

intending to print the last four characters of $a. The problem is that
${param:-word} already has a well-defined meaning: expand to word if the
expanded value of param is unset or null, and $param otherwise.

To use negative offsets that begin with a minus sign, separate the
minus sign and the colon with a space.

Section F: Things to watch out for on certain Unix versions

F1) Why can't I use command line editing in my `cmdtool'?

The problem is `cmdtool' and bash fighting over the input. When
scrolling is enabled in a cmdtool window, cmdtool puts the tty in
`raw mode' to permit command-line editing using the mouse for
applications that cannot do it themselves. As a result, bash and
cmdtool each try to read keyboard input immediately, with neither
getting enough of it to be useful.

This mode also causes cmdtool to not implement many of the
terminal functions and control sequences appearing in the
`sun-cmd' termcap entry. For a more complete explanation, see
that file examples/suncmd.termcap in the bash distribution.

`xterm' is a better choice, and gets along with bash much more
smoothly.

If you must use cmdtool, you can use the termcap description in
examples/suncmd.termcap. Set the TERMCAP variable to the terminal
description contained in that file, i.e.

TERMCAP='Mu|sun-cmd:am:bs:km:pt:li#34:co#80:cl=^L:ce=\E[K:cd=\E[J:rs=\E[s:'

Then export TERMCAP and start a new cmdtool window from that shell.
The bash command-line editing should behave better in the new
cmdtool. If this works, you can put the assignment to TERMCAP
in your bashrc file.

F2) I built bash on Solaris 2. Why do globbing expansions and filename
completion chop off the first few characters of each filename?

This is the consequence of building bash on SunOS 5 and linking
with the libraries in /usr/ucblib, but using the definitions
and structures from files in /usr/include.

The actual conflict is between the dirent structure in
/usr/include/dirent.h and the struct returned by the version of
`readdir' in libucb.a (a 4.3-BSD style `struct direct').

Make sure you've got /usr/ccs/bin ahead of /usr/ucb in your $PATH
when configuring and building bash. This will ensure that you
use /usr/ccs/bin/cc or acc instead of /usr/ucb/cc and that you
link with libc before libucb.

If you have installed the Sun C compiler, you may also need to
put /usr/ccs/bin and /opt/SUNWspro/bin into your $PATH before
/usr/ucb.

F3) Why does bash dump core after I interrupt username completion or
`~user' tilde expansion on a machine running NIS?

This is a famous and long-standing bug in the SunOS YP (sorry, NIS)
client library, which is part of libc.

The YP library code keeps static state -- a pointer into the data
returned from the server. When YP initializes itself (setpwent),
it looks at this pointer and calls free on it if it's non-null.
So far, so good.

If one of the YP functions is interrupted during getpwent (the
exact function is interpretwithsave()), and returns NULL, the
pointer is freed without being reset to NULL, and the function
returns. The next time getpwent is called, it sees that this
pointer is non-null, calls free, and the bash free() blows up
because it's being asked to free freed memory.

The traditional Unix mallocs allow memory to be freed multiple
times; that's probably why this has never been fixed. You can
run configure with the `--without-gnu-malloc' option to use
the C library malloc and avoid the problem.

F4) I'm running SVR4.2. Why is the line erased every time I type `@'?

The `@' character is the default `line kill' character in most
versions of System V, including SVR4.2. You can change this
character to whatever you want using `stty'. For example, to
change the line kill character to control-u, type

stty kill ^U

where the `^' and `U' can be two separate characters.

F5) Why does bash report syntax errors when my C News scripts use a
redirection before a subshell command?

The actual command in question is something like

< file ( command )

According to the grammar given in the POSIX.2 standard, this construct
is, in fact, a syntax error. Redirections may only precede `simple
commands'. A subshell construct such as the above is one of the shell's
`compound commands'. A redirection may only follow a compound command.

This affects the mechanical transformation of commands that use `cat'
to pipe a file into a command (a favorite Useless-Use-Of-Cat topic on
comp.unix.shell). While most commands of the form

cat file | command

can be converted to `< file command', shell control structures such as
loops and subshells require `command < file'.

The file CWRU/sh-redir-hack in the bash-2.05a distribution is an
(unofficial) patch to parse.y that will modify the grammar to
support this construct. It will not apply with `patch'; you must
modify parse.y by hand. Note that if you apply this, you must
recompile with -DREDIRECTION_HACK. This introduces a large
number of reduce/reduce conflicts into the shell grammar.

F6) Why can't I use vi-mode editing on Red Hat Linux 6.1?

The short answer is that Red Hat screwed up.

The long answer is that they shipped an /etc/inputrc that only works
for emacs mode editing, and then screwed all the vi users by setting
INPUTRC to /etc/inputrc in /etc/profile.

The short fix is to do one of the following: remove or rename
/etc/inputrc, set INPUTRC=~/.inputrc in ~/.bashrc (or .bash_profile,
but make sure you export it if you do), remove the assignment to
INPUTRC from /etc/profile, add

set keymap emacs

to the beginning of /etc/inputrc, or bracket the key bindings in
/etc/inputrc with these lines

$if mode=emacs
[...]
$endif

F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on
HP/UX 11.x?

HP/UX's support for long double is imperfect at best.

GCC will support it without problems, but the HP C library functions
like strtold(3) and printf(3) don't actually work with long doubles.
HP implemented a `long_double' type as a 4-element array of 32-bit
ints, and that is what the library functions use. The ANSI C
`long double' type is a 128-bit floating point scalar.

The easiest fix, until HP fixes things up, is to edit the generated
config.h and #undef the HAVE_LONG_DOUBLE line. After doing that,
the compilation should complete successfully.

Section G: How can I get bash to do certain common things?

G1) How can I get bash to read and display eight-bit characters?

This is a process requiring several steps.

First, you must ensure that the `physical' data path is a full eight
bits. For xterms, for example, the `vt100' resources `eightBitInput'
and `eightBitOutput' should be set to `true'.

Once you have set up an eight-bit path, you must tell the kernel and
tty driver to leave the eighth bit of characters alone when processing
keyboard input. Use `stty' to do this:

stty cs8 -istrip -parenb

For old BSD-style systems, you can use

stty pass8

You may also need

stty even odd

Finally, you need to tell readline that you will be inputting and
displaying eight-bit characters. You use readline variables to do
this. These variables can be set in your .inputrc or using the bash
`bind' builtin. Here's an example using `bind':

bash$ bind 'set convert-meta off'
bash$ bind 'set meta-flag on'
bash$ bind 'set output-meta on'

The `set' commands between the single quotes may also be placed
in ~/.inputrc.

G2) How do I write a function `x' to replace builtin command `x', but
still invoke the command from within the function?

This is why the `command' and `builtin' builtins exist. The
`command' builtin executes the command supplied as its first
argument, skipping over any function defined with that name. The
`builtin' builtin executes the builtin command given as its first
argument directly.

For example, to write a function to replace `cd' that writes the
hostname and current directory to an xterm title bar, use
something like the following:

cd()
{
builtin cd "$@" && xtitle "$HOST: $PWD"
}

This could also be written using `command' instead of `builtin';
the version above is marginally more efficient.

G3) How can I find the value of a shell variable whose name is the value
of another shell variable?

Versions of Bash newer than Bash-2.0 support this directly. You can use

${!var}

For example, the following sequence of commands will echo `z':

var1=var2
var2=z
echo ${!var1}

For sh compatibility, use the `eval' builtin. The important
thing to remember is that `eval' expands the arguments you give
it again, so you need to quote the parts of the arguments that
you want `eval' to act on.

For example, this expression prints the value of the last positional
parameter:

eval echo \"\$\{$#\}\"

The expansion of the quoted portions of this expression will be
deferred until `eval' runs, while the `$#' will be expanded
before `eval' is executed. In versions of bash later than bash-2.0,

echo ${!#}

does the same thing.

This is not the same thing as ksh93 `nameref' variables, though the syntax
is similar. I may add namerefs in a future bash version.

G4) How can I make the bash `time' reserved word print timing output that
looks like the output from my system's /usr/bin/time?

The bash command timing code looks for a variable `TIMEFORMAT' and
uses its value as a format string to decide how to display the
timing statistics.

The value of TIMEFORMAT is a string with `%' escapes expanded in a
fashion similar in spirit to printf(3). The manual page explains
the meanings of the escape sequences in the format string.

If TIMEFORMAT is not set, bash acts as if the following assignment had
been performed:

TIMEFORMAT=$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'

The POSIX.2 default time format (used by `time -p command') is

TIMEFORMAT=$'real %2R\nuser %2U\nsys %2S'

The BSD /usr/bin/time format can be emulated with:

TIMEFORMAT=$'\t%1R real\t%1U user\t%1S sys'

The System V /usr/bin/time format can be emulated with:

TIMEFORMAT=$'\nreal\t%1R\nuser\t%1U\nsys\t%1S'

The ksh format can be emulated with:

TIMEFORMAT=$'\nreal\t%2lR\nuser\t%2lU\nsys\t%2lS'

G5) How do I get the current directory into my prompt?

Bash provides a number of backslash-escape sequences which are expanded
when the prompt string (PS1 or PS2) is displayed. The full list is in
the manual page.

The \w expansion gives the full pathname of the current directory, with
a tilde (`~') substituted for the current value of $HOME. The \W
expansion gives the basename of the current directory. To put the full
pathname of the current directory into the path without any tilde
subsitution, use $PWD. Here are some examples:

PS1='\w$ ' # current directory with tilde
PS1='\W$ ' # basename of current directory
PS1='$PWD$ ' # full pathname of current directory

The single quotes are important in the final example to prevent $PWD from
being expanded when the assignment to PS1 is performed.

G6) How can I rename "*.foo" to "*.bar"?

Use the pattern removal functionality described in D3. The following `for'
loop will do the trick:

for f in *.foo; do
mv $f ${f%foo}bar
done

G7) How can I translate a filename from uppercase to lowercase?

The script examples/functions/lowercase, originally written by John DuBois,
will do the trick. The converse is left as an exercise.

G8) How can I write a filename expansion (globbing) pattern that will match
all files in the current directory except "." and ".."?

You must have set the `extglob' shell option using `shopt -s extglob' to use
this:

echo .!(.|) *

A solution that works without extended globbing is given in the Unix Shell
FAQ, posted periodically to comp.unix.shell.

Section H: Where do I go from here?

H1) How do I report bugs in bash, and where should I look for fixes and
advice?

Use the `bashbug' script to report bugs. It is built and
installed at the same time as bash. It provides a standard
template for reporting a problem and automatically includes
information about your configuration and build environment.

`bashbug' sends its reports to bug-bash@gnu.org, which
is a large mailing list gatewayed to the usenet newsgroup gnu.bash.bug.

Bug fixes, answers to questions, and announcements of new releases
are all posted to gnu.bash.bug. Discussions concerning bash features
and problems also take place there.

To reach the bash maintainers directly, send mail to
bash-maintainers@gnu.org.

H2) What kind of bash documentation is there?

First, look in the doc directory in the bash distribution. It should
contain at least the following files:

bash.1 an extensive, thorough Unix-style manual page
builtins.1 a manual page covering just bash builtin commands
bashref.texi a reference manual in GNU tex`info format
bashref.info an info version of the reference manual
FAQ this file
article.ms text of an article written for The Linux Journal
readline.3 a man page describing readline

Postscript, HTML, and ASCII files created from the above source are
available in the documentation distribution.

There is additional documentation available for anonymous FTP from host
ftp.cwru.edu in the `pub/bash' directory.

Cameron Newham and Bill Rosenblatt have written a book on bash, published
by O'Reilly and Associates. The book is based on Bill Rosenblatt's Korn
Shell book. The title is ``Learning the Bash Shell'', and the ISBN number
is 1-56592-147-X. Look for it in fine bookstores near you. This book
covers bash-1.14, but has an appendix describing some of the new features
in bash-2.0.

A second edition of this book is available, published in January, 1998.
The ISBN number is 1-56592-347-2. Look for it in the same fine bookstores
or on the web.

The GNU Bash Reference Manual has been published as a printed book by
Network Theory Ltd (Paperback, ISBN: 0-9541617-7-7, Feb 2003). It covers
bash-2.0 and is available from most online bookstores (see
http://www.network-theory.co.uk/bash/manual/ for details). The publisher
will donate $1 to the Free Software Foundation for each copy sold.

H3) What's coming in future versions?

These are features I hope to include in a future version of bash.

a better bash debugger (a minimally-tested version is included with bash-2.05b)
associative arrays
co-processes, but with a new-style syntax that looks like function declaration

H4) What's on the bash `wish list' for future versions?

These are features that may or may not appear in a future version of bash.

breaking some of the shell functionality into embeddable libraries
a module system like zsh's, using dynamic loading like builtins
better internationalization using GNU `gettext'
date-stamped command history
a bash programmer's guide with a chapter on creating loadable builtins
a better loadable interface to perl with access to the shell builtins and
variables (contributions gratefully accepted)
ksh93-like `nameref' variables
ksh93-like `+=' variable assignment operator
ksh93-like `xx.yy' variables (including some of the .sh.* variables) and
associated disipline functions
Some of the new ksh93 pattern matching operators, like backreferencing

H5) When will the next release appear?

The next version will appear sometime in 2003. Never make predictions.

This document is Copyright 1995-2003 by Chester Ramey.

Permission is hereby granted, without written agreement and
without license or royalty fees, to use, copy, and distribute
this document for any purpose, provided that the above copyright
notice appears in all copies of this document and that the
contents of this document remain unaltered.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
( ``Discere est Dolere'' -- chet )
Live...Laugh...Love
Chet Ramey, ITS, CWRU chet@po.cwru.edu http://tiswww.tis.cwru.edu/~chet/
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
( ``Discere est Dolere'' -- chet )
Live...Laugh...Love
Chet Ramey, ITS, CWRU chet@po.cwru.edu http://tiswww.tis.cwru.edu/~chet/

Csh Programming Considered Harmful

2008-05-28T13:26:00.000-04:00

The following periodic article answers in excruciating detail
the frequently asked question "Why shouldn't I program in csh?".
It is available for anon FTP from perl.com in /pub/perl/versus/csh.whynot.gz

*** CSH PROGRAMMING CONSIDERED HARMFUL ***

Resolved: The csh is a tool utterly inadequate for programming,
and its use for such purposes should be strictly banned!

I am continually shocked and dismayed to see people write test cases,
install scripts, and other random hackery using the csh. Lack of
proficiency in the Bourne shell has been known to cause errors in /etc/rc
and .cronrc files, which is a problem, because you *must* write these files
in that language.

The csh is seductive because the conditionals are more C-like, so the path
of least resistance is chosen and a csh script is written. Sadly, this is
a lost cause, and the programmer seldom even realizes it, even when they
find that many simple things they wish to do range from cumbersome to
impossible in the csh.

1. FILE DESCRIPTORS

The most common problem encountered in csh programming is that
you can't do file-descriptor manipulation. All you are able to
do is redirect stdin, or stdout, or dup stderr into stdout.
Bourne-compatible shells offer you an abundance of more exotic
possibilities.

1a. Writing Files

In the Bourne shell, you can open or dup arbitrary file descriptors.
For example,

exec 2>errs.out

means that from then on, stderr goes into errs file.

Or what if you just want to throw away stderr and leave stdout
alone? Pretty simple operation, eh?

cmd 2>/dev/null

Works in the Bourne shell. In the csh, you can only make a pitiful
attempt like this:

(cmd > /dev/tty) >& /dev/null

But who said that stdout was my tty? So it's wrong. This simple
operation *CANNOT BE DONE* in the csh.

Along these same lines, you can't direct error messages in csh scripts
out stderr as is considered proper. In the Bourne shell, you might say:

echo "$0: cannot find $file" 1>&2

but in the csh, you can't redirect stdout out stderr, so you end
up doing something silly like this:

sh -c 'echo "$0: cannot find $file" 1>&2'

1b. Reading Files

In the csh, all you've got is $<, which reads a line from your tty. What
if you've redirected stdin? Tough noogies, you still get your tty, which
you really can't redirect. Now, the read statement
in the Bourne shell allows you to read from stdin, which catches
redirection. It also means that you can do things like this:

exec 3 exec 4
Now you can read from fd 3 and get lines from file1, or from file2 through
fd 4. In modern, Bourne-like shells, this suffices:

read some_var 0<&3
read another_var 0<&4

Although in older ones where read only goes from 0, you trick it:

exec 5<&0 # save old stdin
exec 0<&3; read some_var
exec 0<&4; read another_var
exec 0<&5 # restore it

1c. Closing FDs

In the Bourne shell, you can close file descriptors you don't
want open, like 2>&-, which isn't the same as redirecting it
to /dev/null.

1d. More Elaborate Combinations

Maybe you want to pipe stderr to a command and leave stdout alone.
Not too hard an idea, right? You can't do this in the csh as I
mentioned in 1a. In a Bourne shell, you can do things like this:

exec 3>&1; grep yyy xxx 2>&1 1>&3 3>&- | sed s/file/foobar/ 1>&2 3>&-
grep: xxx: No such foobar or directory

Normal output would be unaffected. The closes there were in case
something really cared about all its FDs. We send stderr to sed,
and then put it back out 2.

Consider the pipeline:

A | B | C

You want to know the status of C, well, that's easy: it's in $?, or
$status in csh. But if you want it from A, you're out of luck -- if
you're in the csh, that is. In the Bourne shell, you can get it, although
doing so is a bit tricky. Here's something I had to do where I ran dd's
stderr into a grep -v pipe to get rid of the records in/out noise, but had
to return the dd's exit status, not the grep's:

device=/dev/rmt8
dd_noise='^[0-9]+\+[0-9]+ records (in|out)$'
exec 3>&1
status=`((dd if=$device ibs=64k 2>&1 1>&3 3>&- 4>&-; echo $? >&4) |
egrep -v "$dd_noise" 1>&2 3>&- 4>&-) 4>&1`
exit $status;

The csh has also been known to close all open file descriptors besides
the ones it knows about, making it unsuitable for applications that
intend to inherit open file descriptors.

2. COMMAND ORTHOGONALITY

2a. Built-ins

The csh is a horrid botch with its built-ins. You can't put them
together in many reasonable ways. Even simple little things like this:

% time | echo

which while nonsensical, shouldn't give me this message:

Reset tty pgrp from 9341 to 26678

Others are more fun:

% sleep 1 | while
while: Too few arguments.
[5] 9402
% jobs
[5] 9402 Done sleep |

Some can even hang your shell. Try typing ^Z while you're sourcing
something, or redirecting a source command. Just make sure you have
another window handy. Or try

% history | more

on some systems.

Aliases are not evaluated everywhere you would like them do be:

% alias lu 'ls -u'
% lu
HISTORY News bin fortran lib lyrics misc tex
Mail TEX dehnung hpview logs mbox netlib
% repeat 3 lu
lu: Command not found.
lu: Command not found.
lu: Command not found.

% time lu
lu: Command not found.

2b. Flow control

You can't mix flow-control and commands, like this:

who | while read line; do
echo "gotta $line"
done

You can't combine multiline constructs in a csh using semicolons.
There's no easy way to do this

alias cmd 'if (foo) then bar; else snark; endif'

You can't perform redirections with if statements that are
evaluated solely for their exit status:

if ( { grep vt100 /etc/termcap > /dev/null } ) echo ok

And even pipes don't work:

if ( { grep vt100 /etc/termcap | sed 's/$/###' } ) echo ok

But these work just fine in the Bourne shell:

if grep vt100 /etc/termcap > /dev/null ; then echo ok; fi

if grep vt100 /etc/termcap | sed 's/$/###/' ; then echo ok; fi

Consider the following reasonable construct:

if ( { command1 | command2 } ) then
...
endif

The output of command1 won't go into the input of command2. You will get
the output of both commands on standard output. No error is raised. In
the Bourne shell or its clones, you would say

if command1 | command2 ; then
...
fi

2c. Stupid parsing bugs

Certain reasonable things just don't work, like this:

% kill -1 `cat foo`
`cat foo`: Ambiguous.

But this is ok:

% /bin/kill -1 `cat foo`

If you have a stopped job:

[2] Stopped rlogin globhost

You should be able to kill it with

% kill %?glob
kill: No match

but

% fg %?glob

works.

White space can matter:

if(expr)

may fail on some versions of csh, while

if (expr)

works! Your vendor may have attempted to fix this bug, but odds are good
that their csh still won't be able to handle

if(0) then
if(1) then
echo A: got here
else
echo B: got here
endif
echo We should never execute this statement
endif

3. SIGNALS

In the csh, all you can do with signals is trap SIGINT. In the Bourne
shell, you can trap any signal, or the end-of-program exit. For example,
to blow away a tempfile on any of a variety of signals:

$ trap 'rm -f /usr/adm/tmp/i$$ ;
echo "ERROR: abnormal exit";
exit' 1 2 3 15

$ trap 'rm tmp.$$' 0 # on program exit

4. QUOTING

You can't quote things reasonably in the csh:

set foo = "Bill asked, \"How's tricks?\""

doesn't work. This makes it really hard to construct strings with
mixed quotes in them. In the Bourne shell, this works just fine.
In fact, so does this:

cd /mnt; /usr/ucb/finger -m -s `ls \`u\``

Dollar signs cannot be escaped in double quotes in the csh. Ug.

set foo = "this is a \$dollar quoted and this is $HOME not quoted"
dollar: Undefined variable.

You have to use backslashes for newlines, and it's just darn hard to
get them into strings sometimes.

set foo = "this \
and that";
echo $foo
this and that
echo "$foo"
Unmatched ".

Say what? You don't have these problems in the Bourne shell, where it's
just fine to write things like this:

echo 'This is
some text that contains
several newlines.'

As distributed, quoting history references is a challenge. Consider:

% mail adec23!alberta!pixel.Convex.COM!tchrist
alberta!pixel.Convex.COM!tchri: Event not found.

5. VARIABLE SYNTAX

There's this big difference between global (environment) and local
(shell) variables. In csh, you use a totally different syntax
to set one from the other.

In the Bourne shell, this
VAR=foo cmds args
is the same as
(export VAR; VAR=foo; cmd args)
or csh's
(setenv VAR; cmd args)

You can't use :t, :h, etc on envariables. Watch:
echo Try testing with $SHELL:t

It's really nice to be able to say

${PAGER-more}
or
FOO=${BAR:-${BAZ}}

to be able to run the user's PAGER if set, and more otherwise.
You can't do this in the csh. It takes more verbiage.

You can't get the process number of the last background command from the
csh, something you might like to do if you're starting up several jobs in
the background. In the Bourne shell, the pid of the last command put in
the background is available in $!.

The csh is also flaky about what it does when it imports an
environment variable into a local shell variable, as it does
with HOME, USER, PATH, and TERM. Consider this:

% setenv TERM '`/bin/ls -l / > /dev/tty`'
% csh -f

And watch the fun!

6. EXPRESSION EVALUATION

Consider this statement in the csh:

if ($?MANPAGER) setenv PAGER $MANPAGER

Despite your attempts to only set PAGER when you want
to, the csh aborts:

MANPAGER: Undefined variable.

That's because it parses the whole line anyway AND EVALUATES IT!
You have to write this:

if ($?MANPAGER) then
setenv PAGER $MANPAGER
endif

That's the same problem you have here:

if ($?X && $X == 'foo') echo ok
X: Undefined variable

This forces you to write a couple nested if statements. This is highly
undesirable because it renders short-circuit booleans useless in
situations like these. If the csh were the really C-like, you would
expect to be able to safely employ this kind of logic. Consider the
common C construct:

if (p && p->member)

Undefined variables are not fatal errors in the Bourne shell, so
this issue does not arise there.

While the csh does have built-in expression handling, it's not
what you might think. In fact, it's space sensitive. This is an
error

@ a = 4/2

but this is ok

@ a = 4 / 2

The ad hoc parsing csh employs fouls you up in other places
as well. Consider:

% alias foo 'echo hi' ; foo
foo: Command not found.
% foo
hi

7. ERROR HANDLING

Wouldn't it be nice to know you had an error in your script before
you ran it? That's what the -n flag is for: just check the syntax.
This is especially good to make sure seldom taken segments of code
code are correct. Alas, the csh implementation of this doesn't work.
Consider this statement:

exit (i)

Of course, they really meant

exit (1)

or just

exit 1

Either shell will complain about this. But if you hide this in an if
clause, like so:

#!/bin/csh -fn
if (1) then
exit (i)
endif

The csh tells you there's nothing wrong with this script. The equivalent
construct in the Bourne shell, on the other hand, tells you this:

#!/bin/sh -n
if (1) then
exit (i)
endif

/tmp/x: syntax error at line 3: `(' unexpected

RANDOM BUGS

Here's one:

fg %?string
^Z
kill %?string
No match.

Huh? Here's another

!%s%x%s

Coredump, or garbage.

If you have an alias with backquotes, and use that in backquotes in
another one, you get a coredump.

Try this:
% repeat 3 echo "/vmu*"
/vmu*
/vmunix
/vmunix
What???

Here's another one:

% mkdir tst
% cd tst
% touch '[foo]bar'
% foreach var ( * )
> echo "File named $var"
> end
foreach: No match.

8. SUMMARY

While some vendors have fixed some of the csh's bugs (the tcsh also does
much better here), many have added new ones. Most of its problems can
never be solved because they're not actually bugs per se, but rather the
direct consequences of braindead design decisions. It's inherently flawed.

Do yourself a favor, and if you *have* to write a shell script, do it in the
Bourne shell. It's on every UNIX system out there. However, behavior
can vary.

There are other possibilities.

The Korn shell is the preferred programming shell by many sh addicts,
but it still suffers from inherent problems in the Bourne shell's design,
such as parsing and evaluation horrors. The Korn shell or its
public-domain clones and supersets (like bash) aren't quite so ubiquitous
as sh, so it probably wouldn't be wise to write a sharchive in them that
you post to the net. When 1003.2 becomes a real standard that companies
are forced to adhere to, then we'll be in much better shape. Until
then, we'll be stuck with bug-incompatible versions of the sh lying about.

The Plan 9 shell, rc, is much cleaner in its parsing and evaluation; it is
not widely available, so you'd be significantly sacrificing portability.
No vendor is shipping it yet.

If you don't have to use a shell, but just want an interpreted language,
many other free possibilities present themselves, like Perl, REXX, TCL,
Scheme, or Python. Of these, Perl is probably the most widely available
on UNIX (and many other) systems and certainly comes with the most
extensive UNIX interface. Increasing numbers vendors ship Perl with
their standard systems. (See the comp.lang.perl FAQ for a list.)

If you have a problem that would ordinarily use sed or awk or sh, but it
exceeds their capabilities or must run a little faster, and you don't want
to write the silly thing in C, then Perl may be for you. You can get
at networking functions, binary data, and most of the C library. There
are also translators to turn your sed and awk scripts into Perl scripts,
as well as a symbolic debugger. Tchrist's personal rule of thumb is
that if it's the size that fits in a Makefile, it gets written in the
Bourne shell, but anything bigger gets written in Perl.

See the comp.lang.{perl,rexx,tcl} newsgroups for details about these
languages (including FAQs), or David Muir Sharnoff's comparison of
freely available languages and tools in comp.lang.misc and news.answers.

NOTE: Doug Hamilton has a program that he sells for
profit for little toy non-UNIX systems. He calls it 'csh' or the
'hamilton csh', but it's not a csh as it's neither bug nor feature
compatible with the real csh. Actually, he's fixed a great deal, but
in doing so, has created a totally different shell.

How to give each file a common extension using shell script

2008-05-27T11:30:00.002-04:00

Say, you want to rename each file in a directory to .old

just do this:

for i in `ls -1`
do
mv $i $i\.old
done

This will do the trick.

Perl - How to open a gzipped file

2008-05-27T11:16:00.001-04:00

open (FH, "/usr/bin/gzcat $file_name|") or die " Whatever : $! \n ";

Stored procedure and DBI/DBD module for perl

2008-05-21T14:41:00.002-04:00

Folks,
I liked this method to call stored procedure in oracle/mysql through DBI rather than calling sqlplus or mysql and then doing exec stored procedure.

$date_id =$ARGV[0];
$script_name =$ARGV[1];
$type =$ARGV[2]||0;
$status =$ARGV[3]||0;

$csr = $dbh->prepare(q{
BEGIN
stored_procedure_name(:date_id,:script_name,:type,:status);
END;
});
$csr->bind_param(":date_id", $date_id);

$obj->proc_execute($csr , "stored_procedure_name");

$dbh->disconnect;

Hurd and Linux

2008-05-21T10:30:00.001-04:00

Folks,

I got very curious about GRUB and HURD when my laptop crashed when power went down. I found out that GNU has developed it's own kernel for UNIX like OS which is different than any Linux Distros. uses. It is called 'HURD'.

Both are two different kernels.
You can find kernel image for Linux at www.kernel.org
and GNU kernel at http://www.gnu.org/software/hurd/

The Hurd and Linux:
-------------------

People sometimes ask, ``Why did the FSF develop a new free kernel instead of using Linux?'' It's a reasonable question. The answer, briefly, is that that is not the question we faced.

When we started developing the Hurd in 1990, the question facing us was, ``How can we get a free kernel for the GNU system?'' There was no free Unix-like kernel then, and we knew of no other plan to write one. The only way we could expect to have a free kernel was to write it ourselves. So we started.

We heard about Linux after its release. At that time, the question facing us was, ``Should we cancel the Hurd project and use Linux instead?''

We heard that Linux was not at all portable (this may not be true today, but that's what we heard then). And we heard that Linux was architecturally on a par with the Unix kernel; our work was leading to something much more powerful.

Given the years of work we had already put into the Hurd, we decided to finish it rather than throw them away.

If we did face the question that people ask---if Linux were already available, and we were considering whether to start writing another kernel---we would not do it. Instead we would choose another project, something to do a job that no existing free software can do.

But we did start the Hurd, back then, and now we have made it work. We hope its superior architecture will make free operating systems more powerful.

MySQL DBI

2008-05-20T15:37:00.000-04:00

my $xstr='DBI:mysql:database=db_name;host=$host;port=3306';
my $xhd = DBI->connect($xstr, 'deepak' , 'xxx_password' );

How to search for a pattern in every file

2008-05-12T16:49:00.000-04:00

find . -exec grep "Pattern_to_look_for" {} \;

awk or gawk user guide

2008-05-12T16:44:00.001-04:00

http://www.gnu.org/software/gawk/manual/gawk.html#If-Statement

Different Methods to calculate the number of lines in a file

2008-05-12T16:36:00.000-04:00

cat file_name | wc –l
wc –l < file_name
awk '{x++}END{ print x}' file_name
awk 'END{print NR}' file_name
sed –n ‘$=’ file_name

Everything about - cookie -

2008-05-12T15:47:00.000-04:00

Cookie FAQ
This FAQ is to enlighten you to the truth about Cookies. They are not as dangerous as the myths the media likes to popularize but then again, when has the media ever worried about the FAQ's? (Pun intended)

This FAQ is compiled with bits of info grabbed from all over the place but for the most part it's based on mechanical (programming) fact and my experiences with Cookies.

When I first became exposed to the Internet and Web Surfing, I hated Cookies as I was afraid of what they might do or learn about me. The facts set me free of that fear and now I embrace them when I'm surfing as I know the person who uses it has made a decision to serve me better!

What is a Cookie?
How Cookies work.
Are Cookies dangerous?
What information does a Cookie collect from you?
What information can a Cookie get from my computer?
Can a Cookie give my computer a virus?
Can a Cookie delete my hard drive?
Can I refuse to accept a Cookie?
What happens if I refuse to accept a Cookie?
Who can see my Cookies?
Can anything bad happen from Cookies?
Back To FAQ List

--------------------------------------------------------------------------------

What is a Cookie?
A cookie is a text file. That's all. Website designers will use cookies for a variety of reasons. If you go to a website that allows you to customize a page so that it looks the same everytime you visit it, the designer will store these pieces of design information in a Cookie.
If you become a member or some site that wants to make you navigation easy, they will store your membership info in a Cookie so that you are instantly recognized when you visit the site.

Controlled access can be achieved via a Cookie so that you can't view pages unless you have signed in with a UserID and Password. Usually these cookies expire after you leave the site.

There are many ways a cookie can be used, from simply seeing what pages you visit to allowing you to use an on-line shopping cart! Many people balk at the thought of someone seeing what pages of their website you visit. The consideration most people don't stop for here is that it is the Designers website, why shouldn't he be able to tell what you visit? That way he can improve content on popular pages and remove or enhance un-popular pages.
Top

How Cookies work.
A Cookie is a text file. That's it. It can be created via a Perl script, Javascript, Active Server Pages etc. A Cookie is text information that is transferred from the server to your Browser via the HTTP protocol and then stored on your hard drive. It is not an executable file, it is not some nefarious info sniffer from Techno-World, it is only a text file.
If a site uses a Cookie then everytime you visit that site, if the browser has a Cookie stored on it, it transfers that Cookie to that site. The program on the site using the Cookie then access the information and acts upon it.

It is important to understand here that a Cookie will only be transfered to the site that created it. Part of the Cookie is the domain name of the site that created it as well as the path to the program that access it. Unless the domain and path match exactly as they were set, the Cookie IS NOT TRANSFERED! There is no way for someone from one site to see the contents of the Cookie from another site. It's just mechanically not possible.
Top

Are Cookies dangerous?
NO! As I said, it is a text file and that is all. It is not an executable and can't do anything to your computer!
Consider the following:

I can write a Perl program that will broadcast your name and e-mail address to thousands of mailing lists.
I can write a Perl program that will display any personal information you give it to tens of thousands of people by simply accessing a mailing list program.
I can write Javascript that will launch a program on your computer.
I can write Javascript that will close your browser.
I can write Javascript that will launch thousands of copies of your browser program, thereby crashing your computer.
I can write a Java program that will ERASE YOUR HARDDRIVE!!!

Think of all the things I can do to you with Perl, Java and Javascript. Think of how many site you visit that interact with a Perl CGI application. Think of how many thousands of pages out there have Javascript embeded in them. Think of how many Java applets you download and run! You download and run all those pages on your browser without giving a single thought to what the underlying Javascript can do to your computer.
Cookies are text files as I've said, they can do nothing except sit on your computers hard drive until called or they expire.
Top

What information does a Cookie collect from you?
NOTHING!!! A Cookie collects no information whatsoever. The only information in a Cookie is information from the website designer or information that you have entered into a CGI/Javascript form. Information that you enter can be placed in a Cookie, the Cookie doesn't get the information on it's own. It is mechanically impossible for a Cookie to get ANY information from your computer. That's like saying the notebook on your nighttable is collecting information about you while you are asleep.
Top

What information can a Cookie get from my computer?
NOTHING!!! As I said, a Cookie is a text file, plain and simple. It is not an executable program that can be run therefore it can not gather information. The page your looking at right now could, however, aready have searched your hard drive for your banking records via the use of a Java applet.........never thought of that did you?
Just so you know, it hasn't. I don't go in for that under handed dealing. Just look at the source code for this page and you'll see there is no Java applet in it.
Top

Can a Cookie give my computer a virus?
NO!!! Cookies are not executable's. For something to pass on a virus, you must first execute a program or applet. You can not get a virus from a text file. Just like you can't get a cold from watching a winter scene on television!
With Java, I could have written code into the page that when you try to visit the next page or close the browser, your hard drive gets erased.
Top

Can a Cookie delete my hard drive?
NO!!! Cookies can not delete your hard drive. Cookies are text files only and are not executable, therefore they can not do anything to your computer! See the topic above.
Top

Can I refuse to accept a Cookie?
Yes. Older brwosers accepted Cookies automatically. MSIE3.0 and Netscape3.0 both allow you to accept or reject Cookies. V4.0 of these browsers allow you to always accept Cookies, choose to accept or reject Cookies or never accept Cookies. Here are the instructions for these V4.0 browsers:

Explorer => Toolbar: View=>Internet Options=>Advanced then scroll down to "Cookies"

Navigator => Toolbar: Options=>Network Preferences=>Protocols and follow the instructions.

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What happens if I refuse to accept a Cookie?
The site designer calls the F.B.I. who call the S.W.A.T. team.....
Just kidding! Nothing happens if you refuse to accept a Cookie. Refusing to accept a Cookie will only, at worst, make your surfing less personalized.

If you refuse a Cookie from a site which you registered as a member of, refusing a Cookie may mean that you can't access the site.
Top

Who can see my Cookies?
When a Cookie is transferred to your browser, part of it's content is the domain name of the server that placed it there. Another part of the Cookie data is the path to the program that placed the Cookie.
When you visit a site that checks for Cookies, the browser looks at the request and determines the name of the server and the path to the program. If a Cookie exists that has the same domain name and the same path then obviously that program is allowed to access that Cookie because it placed it there in the first place!

If the domain name and path do not match exactly, then the browser WILL NOT TRANSMIT THE COOKIE!!!. This means that, mechanically and logically, the Cookie will only be made available to an authorized program on the host server.

No one except an authorized person can see the Cookie therefore no one can look at or take information from another websites Cookie!
Top

Can anything bad happen from Cookies?
From Cookies themselves? No!
As we have amply covered in this FAQ, a Cookie can not do anything bad to you or your computer. How the information is used, however, is something different. If there is any personal data stored in a Cookie, the only way it got there is because YOU provided it. If you fill out a form on a website and provide sensitive information such as your name, address, email, credit card number....then that data MIGHT be stored in a Cookie. Not always but sometimes. The concern that most Cookie detractors have is if a website stores information on an individual, for example, info on a person who navigates through a sex site. This information (and the only way then have it is becuase you gave it to them in the first place) could concievably be subpoenaed by a law enforcement agency or sold to a mailing list or a religious activist group. This, however, has nothing to do with Cookies. It's about individuals and the law.

Remember, I can track you and get info on you with ASP, Java, Javascript, Python, Perl, PHP and C/C++ and you never even have to accept or reject a single Cookie!

Sun Solaris One liners

2008-05-09T12:07:00.000-04:00

Unix/Solaris: One-Liners
Source: http://www.kevlo.com/~ebs/unix_commands.txt

Listed here are a bunch of unix commands.

--> change file date stamp
touch –t 199906042020 filename

--> move partitions
ufsdump 0f - /dev/rdsk/c0t0s0s0 | (cd /home; ufsrestore xv -)

--> lay down file system with 1% minfree and inode density
newfs –m1 –i81920 /dev/rdsk/c0t0d0s0

--> check file system
fsck /dev/rdsk/c0t0d0s0

Q: starting sybase
login as sybase, run: ./install/RUN_SYBASE

Q: logging in as sybase sa
isql -U sa

--> dump a partition and pipe to gzip. Watch > 2GB limit
ufsdump 0f - /home | gzip - >/tmp/home.dump.gz

--> rewind offline a tape
mt –f /dev/rmt/0 rewoffl

--> only allow 300MB for user /tmp access
swap - /tmp tmpfs – yes SIZE=300M

--> verbose interactive restore
ufsrestore –ivf /dev/rmt/1

--> remove a printer from a class
lpadmin –p level5-line1 –r level5-line

--> truss a command
truss –-f -–o /tmp/log.txt

--> [DB] feed a script into sybase
isql –Urfe_xfer -Uuser -Ppassword -isqlscript >>blah.txt

--> make a printer class
lpadmin –p level5-line1 –c level5-line

--> remove level2-line2 printer from printer class level2-line
lpadmin -p level2-line2 -r level2-line

--> add level2-line3 to printer class
lpadmin -c level2-line -p level2-line3

--> [DB] how to change your password in isql
sp_password password, password-new

--> move a directory
tar cf - ./games | (cd /tmp; tar xvBpf - )

--> [DB] run a sybase script, and dump to file
$ISQL -i$SCRIPTFILE -U$USER -D$DATABASE -P$PASS_ENC >> $SCRIPTLOGFILE

--> move a directory to another server
tar cf - ./games | rsh brucey cd /tmp\; tar xvBpf -

--> check for SUID SGID files
ncheck -F ufs -s /dev/dsk/c3t0d0s

-- remove core files
find / -name core –exec rm –f {} \; -o –fstype nfs –prune

--> rebuild man pages
catman –w –M man-page-directory or /usr/lib/makewhatis

--> vi command to show special characters
: set list

--> adding an account
useradd -u 120 –g dls -d /apps/dls –s /bin/ksh -c "comment" -m dls

--> create a mysql database
mysqladmin -uroot -ppassword create ebs

--> starting mysql database
/etc/rc.d/init.d/mysql.server start
/usr/local/bin/safe_mysqld

--> Invoke CPAN module install
perl –MCPAN –eshell

--> dump to zip
ufsdump 0f - /filesystem | /opt/local/gzip - > /tmp/dump.gz

--> shutdown mysql databse
/usr/local/bin/mysqladmin shutdown -ppassword
/etc/rc.d/init.d/mysql.server stop

--> test the loading of a module
PERL_DL_DEBUG=255 perl -e 'use CGI;'

--> shows open files
fuser –cu /

--> Writing a Daemon:
1. edit /etc/services
add service and port.
2. edit /etc/inetd.conf
add in: edwardd stream tcp nowait root /bin/sh /bin/sh /home/sextone/bin/SERVER.mine
3. kill –HUP inetd.conf

--> how to mount a file system
mount /dev/dsk/c3t0d0s4 /apps/data/easysoft/DEVT

--> look at sar log
sar –f /var/adm/sa/sa24

--> write file checksums and size
cksum filename

--> show storage array info
ssaadm display /dev/rdsk/c1t5d2s0
--> show all disks on device d
luxadm display d

--> examine for a specific OS finerprint
nmap –sS -p 80 -O -v = examine OS

--> show print jobs
/usr/ucb/lpq –Plevel6

--> Scan for known ports. log it. do OS scan.
nmap –sS -F -o foo.log -v -O www.foo.com//24 =

--> show status of printer
/usr/ucb/lpc status

--> make a swap file:
dd if=/dev/zero of=swapfile bs=1024 count=65535
mkswap ./swapfile
chmod 600 ./swapfile
swapon ./swapfile

--> show open files for process
lsof –p PID

--> show open files for all TCP connections
lsof –iTCP

--> show open files for internet address
lsof -iTCP@10.20.2.9

--> as above
lsof -i @10.20.2.122

--> examine tcp ports
lsof -iTCP@sarah:1-50000

--> show open files for user.
lsof –u username

--> show processes that has the file in use.
lsof /apps/cms/ECMS-Server

--> show open files and retry every 5 seconds
lsof –p process-id –r 5

--> mount a floppy
mount -t vfat /dev/fd0 /mnt/floppy

--> check here for debugging processes and errno.h for errors
/usr/include
/usr/include/sys
/usr/include/sys/errno.h

--> scp a whole directory, preserve mods
sudo scp -prv devel webadmin@203.19.123.140:/home/httpd/cgi-bin

--> take processor 2 and 3 offline.
psradm -f 2 3
--> show processor stats verbose.
psrinfo –v

--> how to skip grant tables in mysql (over ride security)
/usr/local/libexec/mysqld -Sg

--> how to feed in an SQL program
mysql
--> rm all files in directories
find . -type f -exec rm {} \;

--> dump packets to a capture file
sudo snoop –o /tmp/tcp.txt cp

--> backup one liner
tar cvf - /home/ebs | gzip - > ebs.tar.gz

--> Look at selected packets in capture file
sudo snoop -i /tmp/tcp.txt

--> unzip and pipe to tar
gzip -dc
--> watch packets from two servers.
snoop sarah brucey

--> enable ip masquerading
/sbin/ipchains -P forward DENY
/sbin/ipchains -A forward -s 10.100.100.100/8 -j MASQ

-> view su log file
cat /var/adm/sulog

--> establish a default router or gateway.
echo "sagacity.com" > /etc/defaultrouter
echo "10.100.100.100 sagacity.com sagacity" >> /etc/hosts
change /etc/nsswitch.conf so that hosts has files, dns
edit resolv.conf put in
search .
nameserver 203.7.132.98

--> turn off automounter on /export/home.
vi /etc/auto_master, comment out /export/home

--> configuration file for sudoers
/opt/local/etc/sudoers

--> building ssh-1.2.27 on x86Solaris2.6 needed a few things:
/usr/openwin/bin in path
/usr/xpg4/bin in path
declare AR="/usr/xpg4/bin/ar"
declare NM_PATH="/usr/xpg4/bin/nm"

--> snoop network packets and get size and time stamp entries.
snoop -S -ta empa1

--> access perl CPAN
perl -MCPAN -e shell
install DBI

--> search for no password entries and lock all accounts.
for i in `passwd –sa | grep NP | awk ‘{print $1’`
do
echo “locking $i”
passwd –l $i
done

--> delete from a tar
tar --delete -f fs_backup_Sunday.tar home/ebs/tmp

--> Example on backing up files to tape. Must specify non rewinding, else you will over-write the files.
for file in `ls`
do
echo "sending $file to tape..."
echo `date`
tar cvpf /dev/rmt/0n $file
done

--> making/adding a partition.
1. use fdisk to make a parition.
2. mkfs -t ext2 -c /dev/hda11
3. mount -t ext2 /dev/hda11 /opt2
4. update /etc/fstab

--> rebuild the windex file
catman –w –M /usr/share/man

--> execute tar on remote host sarah and send tarball to standard output,
which becomes standard input for tar xvf – and the file gets dumped locally,
in this case on crawl. you have to cd to dir before tar or else you
will include path in tar
ssh maggie "cd $DIRNAME; tar cvf - $BASENAME" | (cd $TPATH; tar xvf - )

--> dump a remote filesystem and send it to local tape drive.
ssh -–x $fw /usr/sbin/ufsdump 0cf - $fs | dd obs=63k of=$TAPE

--> encrypt filename 1 and output to 1.crypt file
crypt < 1 > 1.crypt ; rm 1

--> decrypt filename 1.crypt and stdout to screen
crypt < 1.crypt

--> send a file to tape
tar cvpf /dev/rmt/0 filename

--> quicker way to search and replace in vi
: %s/existing/new/g

--> shows where and which shared library files an application uses.
ldd binary

--> shell script stuff:
# repeat a command 100 times
x=100
while [ $x -gt 0 ]
do
command
x=$(($x-1))
done

--> Something very important to remember about partitions
It is important to note that Cylinder 0 contains the disklabel, which
contains the partition table. A normal filesystem can be placed
starting at Cylinder 0, since it will not touch the disklabel.
If you lay down a raw device, for a database, over Cylinder 0,
then you will completely lose all your partitions. You will then
have to restore the disklabel, and backup from tape if you happen to do this.

--> move a partition
find . |cpio -pdm /apps

--> cron structure
min hour day-of-month month weekday command

--> PatchDiag Tool. Get patches from:
http://sunsolve.sun.com/private-cgi/patchpage.pl
patchdiag.xref is available at: http://sunsolve.sun.com/sunsolve/patchdiag/
/opt/local/bin/patchdiag -x /opt/local/lib/patchdiag.xref > patchdiag.`uname -n`

--> command showing system parameters
/usr/sbin/sysdef

--> Get Ambient Temperature of Server
/usr/platform/SUNW,Ultra-4/sbin/prtdiag -v

--> good ps formatting showing percent cpu first.
ps -edf -o pcpu,pid,user,arg

--> full details on ps
/usr/bin/ps –A -o user,pid,pcpu,pmem,vsz,rss,tty,s,stime,time,args

--> chown the hidden files as well.
find . -print -exec chown -R sextone:staff {} \;

--> The nsradmin command is a command-line based administrative
program for the NetWorker system. Normally nsradmin monitors
and modifies NetWorker resources over the network.
/usr/sbin/nsr/nsradmin

--> Spray a server
-c number of packets
-d delay in microseconds
-l pakcet size in bytes
/usr/sbin/spray -c 1 –d 20 -l 4096 maggie

--> Turn on bold.
bold=`tput smso`
offbold=`tput rmso`
echo "${bold}You must be the \"root\" user to run this script.${offbold}"

--> good way to send a dir to tape
tar cf /dev/rmt/0n directory

--> example of bringing up an interface
ifconfig hme0:1 inet 10.2.25.52 up

--> show all connections
netstat –f inet

--> rpcinfo makes an RPC call to an RPC server and reports
what it finds.
rpcinfo -b 390109 2 | sort -u

--> rewind a tape fast
< /dev/rmt/0

--> show loaded modules
/usr/sbin/modinfo

--> find world readable files and dirs
find / -type d –perm -2 –print
find . -type f –perm -2 -print

--> adding in a boot alias, eg:
boot sarahroot1 –s
nvalias sarahroot1 /sbus@1f,0/sunw,fas@e,8800000/sd@9,0:a

--> clever way to archive
tar cvf - `find . –print` >/tmp/dumpfile.tar
tar xvf -
--> tee to a file
echo "Start Date/Time: `date`" | tee -a $LOG_FILE

--> read a snoop file
snoop -i anz-telnet.snoop

--> write a snoop log (this will count the number of connections, which is pretty neat).
snoop –osnoop.log sarah

--> set default run level. 5 for gui.
/etc/inittab

--> show all exported filesystems
showmount -e crawl

--> shows all configurable variables for tcp interface.
sudo ndd -get /dev/tcp
- ?
eg:
sudo ndd -get /dev/tcp tcp_conn_req_max_q
128
ndd /dev/arp \?
ndd /dev/ip \?
ndd /dev/tcp \?
ndd /dev/udp \?
ndd /dev/icmp \?

--> set sticky bit on group files, only the owner can change the mode.
--> the +l is mandatory file and record locking while a program
--> is accessing that file.
chmod g+s,+l file

--> print duplex landscape 4 qudrant printing
mpage –t –l –4

--> install a patch
installpatch .

--> check to see if a patch has been installed
showrev –p |grep package name

--> unzip, untar in a /tmp directory
zcat 104708-16.tar.gz | ( cd /tmp; sudo tar xvf - )

--> check out revision level on ssa controller
/usr/sbin/ssaadm display controller

--> unzip and untar a file without having to create an intermediate tar file
sudo gzip -dc /tmp/270599/post-EOD.tar.gz |tar xvf -

--> selectively extract from a tar archive
tar xvf /tmp/iona.tar ./iona/.sh_history

--> send a bunch of files to tape
tar cf /tmp/rules.tar ruleb* objects.C *.W

--> examine section 5 of man
man -s 5 signal

--> shows signals and definitions of structures, eg sigaction
/usr/include/sys/signal.h

--> location of the limits file on solaris
/usr/include/limits.h

--> send an attachment via email from command prompt
uuencode file.tar.gz file.tar.gz | mailx –s “backup” root@crawl

--> zero a file
cat /dev/null > isam.log

--> good way to restore from cdrom a binary file
zcat < /cdrom/cdrom0/Solaris_2.6/Product/SUNWcsu/install/reloc.cpio.Z |
cpio –idm usr/lib/fs/ufs/ufsrestore

--> running su as a user then ssh
su - dls-PROD -c "/opt/local/bin/ssh drp-stagger \"cd /tmp; /bin/ls\" "

--> verify a newfs format
sudo newfs –Nv /dev/md/dsk/d96

--> making lost_found. must be 8192 bytes in size.
mkdir ./lost+found;chown root ./lost+found; chgrp root ./lost+found ;chmod 700 ./lost+found’; cd ./lost+found
nofiles=0 ; while [ "$nofiles" -le 650 ] ; do ; /usr/ucb/touch $nofiles ; nofiles=`expr $nofiles + 1` ; done

--> execute lynx
lynx -cfg /usr/lib/lynx.cfg

--> sed search example
sed '/Sep\ 25/!d; /castill/!d' /var/log/syslo

-->should only be used at the EEPROM
boot –r
--> should be used at single user mode
reboot -- -r
--> should be used in multiuser mode
touch /reconfigure

--> performing a remote dump

find MFASYS
|cpio -oc |gzip -c
|ssh brucey -l chaup dd obs=18k of=/dev/rmt/0n

- to extract -
cd /ssa/emphasys/sybase/dump
dd ibs=18k if=|gunzip -c |cpio –idc

--> boot block located here.
/usr/platform/`uname –i`/lib/fs/ufs

--> getting a server on the network
add hosts entry for IP address
clear configs: ifconfig pe0 unplumb
ifconfig pe0 10.20.2.27 netmask 255.0.0.0 up
route add default 10.20.0.1 1
verify the routing table: netstat –rn
add resolv.conf entry: domain rabobank.com.au nameserver 192.192.192.252
edit /etc/nsswitch.conf change hosts to files, dns

lesson here is to unplumb interface, and let ifconfig setup the routing.
if you specify an ip address and a netmask it will manage
the routing and the broadcasting.

--> find all, files associated with PID 22240
/usr/proc/bin/pfiles 22240
find file based on inode
find –i number
“ncheck –i number

--> good redirection example
./a.out trash

--> synchronize files from one server to another. This is useful for
synchronizing database dump files, binary files, etc. This is definitely a powerful tool.

rsync -avz -e ssh --rsync-path="/usr/local/bin/rsync" `pwd` myhost.com:/home/ebs/public_html

--> Example Awk Script

# run with awk -f/tmp/1.awk /etc/group

BEGIN { FS = ":" }
{ print $1 | "sort" }
{ nlines++ }
END { print nlines }

--> awk example.
awk '/#/ {print "Got a comment"}' /etc/hosts

--> delete every 2nd field in file
awk '{$2= ""; print}' datafile > datafile.new

--> awk average/standard deviation program

x1 += $1
x2 += $1*$1

END {
x1 = x1/NR
x2 = x2/NR
sigma = sqrt(x2 - x1*x1)
if (NR > 1) std_err = sigma/sqrt(NR - 1)
print "Number of points = " NR
print "Mean = " x1
print "Standard Deviation = " sigma
print "Standard Error = " std_err

http://www.unixguide.net/unix/programming/

2008-05-08T17:01:00.001-04:00

http://www.unixguide.net/unix/programming/

Unix Tricks

2008-05-07T13:05:00.001-04:00

1)

From within an executing script, how do I find the directory where the script lives?

A simple pwd doesn't work because it gives the Present Working Directory, and we want to know the directory where the script actually resides on disk. I can't remember the previous solution I came up with, but here's another solution that should work:

#!/bin/bashdir=$(echo $0 | sed -e "s,^$[^/]$,$(pwd)/\1,")echo I live in $dir
Here how it works (hopefully). $0 is the name of the script as it was executed, so this may be foo.sh, ./foo.sh, /tmp/foo.sh, etc.. This gets sent to sed, which then uses a basic regular expression that says "If the first character of $0 was NOT a forward slash, then prepend $0 with my present working directory ($(pwd)) followed by whatever that first character was (\1), then assign this new value to dir". If the first character in $0 is a forward slash, then we were invoked via an absolute path and so we don't want to change anything.

2.

How do I copy a directory structure from one machine to another?

$ tar cf - some_directory | ssh kramer "( cd /path/to/destination; tar xf - )"
tar cf - some_directory creates a tar file of some_directory but the dash (-) tells tar to write to STDOUT instead of writing to an actual file on disk. The STDOUT from the first tar command is piped to STDIN of the next command. The right hand side of the pipe says to log into the host kramer using ssh and run the commands cd and tar xf -. The trick is with the commands "( cd /path/to/destination; tar xf - )". The parens create a subshell, in which the current directory is changed to /path/to/destination, and tar xf - reads from STDIN and extracts the tar file. This STDIN is the same STDIN that was sent to us over the pipe from STDOUT of the first tar command. Thus the directory structure on jerry gets tar'd up, transfered to kramer, then extracted all in one fell swoop.

3)

How do I diff two files on different machines (using Bash)?

$ diff <(ssh -n george cat /etc/passwd) <(ssh -n kramer cat /etc/passwd)
This is just the Bash Process Substitution trick.

How can I run a shell script on a remote host without copying the script out?

One way would be:

jerry:~$ cat myscript.sh | ssh kramer /bin/sh
This one is pretty simple how it works, but it is often overlooked as an option for getting things done. The shell script is written to STDOUT. /bin/sh is executed on the remote server, and it reads myscript.sh on STDIN, thus executing the local copy of the script. This is way convient for some things. The only problem I see with this one is that you can't pass command line arguments to the script.

How can I run long pipe lines of commands on a remote host via SSH without escaping all the meta characters?

jerry:~$ ssh kramer <The only tricks here are the use of a bash here document, and the fact that the command line is typed directly into ssh's STDIN so there's no need to escape things like pipes and semi-colons, etc. However, notice that you do still need to escape dollar signs because they'll still be interpreted as shell variables.

How do I change every occurance of a string in multiple files?

Why, use perl pie!

perl -p -i -e 's/jerry/george/g' *.txt
See perl -h for a description of the flags.

How UNIX/LINUX boot/initialization works

2008-04-25T14:04:00.001-04:00

Folks,

Although, it is a 'man init' from the Solaris prompt but it great read to understand the process of initialization.

System Administration Commands init(1M)

NAME
init, telinit - process control initialization

SYNOPSIS
/sbin/init [0123456abcQqSs]

/etc/telinit [0123456abcQqSs]

DESCRIPTION
init is a general process spawner. Its primary role is to
create processes from information stored in the file
/etc/inittab.

Run Level Defined
At any given time, the system is in one of eight possible
run levels. A run level is a software configuration under
which only a selected group of processes exists. Processes
spawned by init for each of these run levels are defined in
/etc/inittab. init can be in one of eight run levels, 0-6
and S or s (S and s are identical). The run level changes
when a privileged user runs /sbin/init. This sends appropri-
ate signals to the original init spawned by the operating
system at boot time, saying which run level to invoke.

init and System Booting
When the system is booted, init is invoked and the following
occurs. First, it reads /etc/default/init to set environment
variables. This is typically where TZ (time zone) and
locale-related environments such as LANG or LC_CTYPE get
set. (See the FILES section at the end of this page.) init
then looks in /etc/inittab for the initdefault entry (see
inittab(4)). If the initdefault entry:

exists
init usually uses the run level specified in that
entry as the initial run level to enter.

does not exist
/etc/inittab, init asks the user to enter a run level
from the system console.

S or s
init goes to the single-user state. In this
state, the system console device (/dev/console)
is opened for reading and writing and the com-
mand /sbin/su, (see su(1M)), is invoked. Use
either init or telinit to change the run level
of the system. Note that if the shell is ter-
minated (using an end-of-file), init only re-
initializes to the single-user state if
/etc/inittab does not exist.

SunOS 5.9 Last change: 21 Feb 2002 1

System Administration Commands init(1M)

0-6 init enters the corresponding run level. Run
levels 0, 5, and 6 are reserved states for shut-
ting the system down. Run levels 2, 3, and 4 are
available as multi-user operating states.

If this is the first time since power up that init has
entered a run level other than single-user state, init first
scans /etc/inittab for boot and bootwait entries (see init-
tab(4)). These entries are performed before any other pro-
cessing of /etc/inittab takes place, providing that the run
level entered matches that of the entry. In this way any
special initialization of the operating system, such as
mounting file systems, can take place before users are
allowed onto the system. init then scans /etc/inittab and
executes all other entries that are to be processed for that
run level.

To spawn each process in /etc/inittab, init reads each entry
and for each entry that should be respawned, it forks a
child process. After it has spawned all of the processes
specified by /etc/inittab, init waits for one of its descen-
dant processes to die, a powerfail signal, or a signal from
another init or telinit process to change the system's run
level. When one of these conditions occurs, init re-examines
/etc/inittab.

inittab Additions
New entries can be added to /etc/inittab at any time; how-
ever, init still waits for one of the above three conditions
to occur before re-examining /etc/inittab. To get around
this, init Q or init q command wakes init to re-examine
/etc/inittab immediately.

When init comes up at boot time and whenever the system
changes from the single-user state to another run state,
init sets the ioctl(2) states of the console to those modes
saved in the file /etc/ioctl.syscon. init writes this file
whenever the single-user state is entered.

Run Level Changes
When a run level change request is made, init sends the
warning signal (SIGTERM) to all processes that are undefined
in the target run level. init waits five seconds before for-
cibly terminating these processes by sending a kill signal
(SIGKILL).

When init receives a signal telling it that a process it
spawned has died, it records the fact and the reason it died
in /var/adm/utmpx and /var/adm/wtmpx if it exists (see
who(1)). A history of the processes spawned is kept in
/var/adm/wtmpx.

SunOS 5.9 Last change: 21 Feb 2002 2

System Administration Commands init(1M)

If init receives a powerfail signal (SIGPWR) it scans
/etc/inittab for special entries of the type powerfail and
powerwait. These entries are invoked (if the run levels per-
mit) before any further processing takes place. In this way
init can perform various cleanup and recording functions
during the powerdown of the operating system.

Environment Variables in /etc/defaults/init
You can set default values for environment variables, for
such items as timezone and character formatting, in
/etc/default/init. See the FILES section, below, for a list
of these variables.

telinit
telinit, which is linked to /sbin/init, is used to direct
the actions of init. It takes a one-character argument and
signals init to take the appropriate action.

SECURITY
init uses pam(3PAM) for session management. The PAM confi-
guration policy, listed through /etc/pam.conf, specifies the
session management module to be used for init. Here is a
partial pam.conf file with entries for init using the UNIX
session management module.

init session required pam_unix_session.so.1

If there are no entries for the init service, then the
entries for the "other" service will be used.

OPTIONS
0 Go into firmware.

1 Put the system in system administrator mode. All local
file systems are mounted. Only a small set of essen-
tial kernel processes are left running. This mode is
for administrative tasks such as installing optional
utility packages. All files are accessible and no
users are logged in on the system.

2 Put the system in multi-user mode. All multi-user
environment terminal processes and daemons are
spawned. This state is commonly referred to as the
multi-user state.

3 Extend multi-user mode by making local resources
available over the network.

4 Is available to be defined as an alternative multi-
user environment configuration. It is not necessary
for system operation and is usually not used.

SunOS 5.9 Last change: 21 Feb 2002 3

System Administration Commands init(1M)

5 Shut the machine down so that it is safe to remove the
power. Have the machine remove power, if possible.

6 Stop the operating system and reboot to the state
defined by the initdefault entry in /etc/inittab.

a, b, c
process only those /etc/inittab entries having the a,
b, or c run level set. These are pseudo-states, which
may be defined to run certain commands, but which do
not cause the current run level to change.

Q, q Re-examine /etc/inittab.

S, s Enter single-user mode. This is the only run level
that doesn't require the existence of a properly for-
matted /etc/inittab file. If this file does not exist,
then by default, the only legal run level that init
can enter is the single-user mode. When in single-user
mode, the filesystems required for basic system opera-
tion will be mounted. When the system comes down to
single-user mode, these file systems will remain
mounted (even if provided by a remote file server),
and any other local filesystems will also be left
mounted. During the transition down to single-user
mode, all processes started by init or init.d scripts
that should only be running in multi-user mode are
killed. In addition, any process that has a utmpx
entry will be killed. This last condition insures that
all port monitors started by the SAC are killed and
all services started by these port monitors, including
ttymon login services, are killed.

FILES
/dev/console
System console device.

/etc/default/init
Contains environment variables and their default
values. For example, for the timezone variable, TZ,
you might specify TZ=US/Pacific. The variables are:

TZ Either specifies the timezone information (see
ctime(3C)) or the name of a timezone information
file /usr/share/lib/zoneinfo.

Refer to the TIMEZONE(4) man page before chang-
ing this setting.

CMASK The mask (see umask(1)) that init uses and that
every process inherits from the init process. If
not set, init uses the mask it inherits from the

SunOS 5.9 Last change: 21 Feb 2002 4

System Administration Commands init(1M)
kernel. Note that init always attempts to apply
a umask of 022 before creating a file, regard-
less of the setting of CMASK.

LC_CTYPE
Character characterization information.

LC_MESSAGES
Message translation.

LC_MONETARY
Monetary formatting information.

LC_NUMERIC
Numeric formatting information.

LC_TIME
Time formatting information.

LC_ALL
If set, all other LC_* environmental variables
take-on this value.

LANG If LC_ALL is not set, and any particular LC_* is
also not set, the value of LANG is used for that
particular environmental variable.

/etc/initpipe
A named pipe used for internal communication.

/etc/inittab
Controls process dispatching by init.

/etc/ioctl.syscon
ioctl states of the console, as saved by init when
single-user state is entered.

/var/adm/utmpx
User access and administration information.

/var/adm/wtmpx
History of user access and administration information.

ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:

SunOS 5.9 Last change: 21 Feb 2002 5

System Administration Commands init(1M)

____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|

SEE ALSO
login(1), sh(1), stty(1), who(1), shutdown(1M), su(1M),
ttymon(1M), ioctl(2), kill(2), ctime(3C), pam(3PAM), init-
tab(4), pam.conf(4), TIMEZONE(4), utmpx(4), attributes(5),
pam_authtok_check(5), pam_authtok_get(5),
pam_authtok_store(5), pam_dhkeys(5), pam_passwd_auth(5),
pam_unix(5), pam_unix_account(5), pam_unix_auth(5),
pam_unix_session(5), termio(7I)

DIAGNOSTICS
If init finds that it is respawning an entry from
/etc/inittab more than ten times in two minutes, assumes
that there is an error in the command string in the entry,
and generates an error message on the system console. It
will then refuse to respawn this entry until either five
minutes has elapsed or it receives a signal from a user-
spawned init or telinit. This prevents init from eating up
system resources when someone makes a typographical error in
the inittab file, or a program is removed that is referenced
in /etc/inittab.

NOTES
init and telinit can be run only by a privileged user.

The S or s state must not be used indiscriminately in
/etc/inittab. When modifying this file, it is best to avoid
adding this state to any line other than initdefault.

If a default state is not specified in the initdefault entry
in /etc/inittab, state 6 is entered. Consequently, the sys-
tem will loop by going to firmware and rebooting continu-
ously.

If the utmpx file cannot be created when booting the system,
the system will boot to state "s" regardless of the state
specified in the initdefault entry in /etc/inittab. This can
occur if the /var file system is not accessible.

When a system transitions down to the S or s state, the
/etc/nologin file (see nologin(4)) is created. Upon subse-
quent transition to run level 2, this file is removed by a
script in the /etc/rc2.d directory.

init uses /etc/initpipe, a named pipe, for internal communi-
cation.

SunOS 5.9 Last change: 21 Feb 2002 6

System Administration Commands init(1M)

The pam_unix(5) module might not be supported in a future
release. Similar functionality is provided by
pam_authtok_check(5), pam_authtok_get(5),
pam_authtok_store(5), pam_dhkeys(5), pam_passwd_auth(5),
pam_unix_account(5), pam_unix_auth(5), and
pam_unix_session(5).

Renaming all files in folder - Unix

2008-04-25T10:05:00.000-04:00

Say, if you want to rename all the files in a folder and add an extension, use this

for file in *.pl ; do mv $file `echo $file | sed 's/$.*\.$pl/\1ppl/'` ; done

This converts all the files in this folder from *.pl to *.ppl

Pretty cool site for perl reading

2008-04-04T16:53:00.000-04:00

http://perl.active-venture.com/

Good read about, How to handle CSV type of files from perl DBI module:

2008-04-04T14:17:00.000-04:00

http://www.mathematik.uni-ulm.de/help/perl5/doc/DBD/CSV.html

5 important functions in perl

2008-04-04T10:31:00.001-04:00

split/join
unpack/pack
seek (fseek function)

pack() and unpack function in PERL

2008-04-04T10:24:00.002-04:00

Content of test-file.txt
------------------------
20080331EJUSD00 0003372500000010750000000000000000000000
20080331 SUSD0000 87673600001148531000000000000000000000
20080331XZUSD00000 0000000000000000000000000000000000000
200 0331XZUSD0000000000000000000000000000000000000000000
20 0331XZUSD0000000000000000000000000000000000000000000

Script name: try-unpack.pl

#!/usr/bin/perl

use warnings;
use strict;

my $xf = './test-file.txt';

open FH, $xf or die " Can not open the file : $! \n";
while()
{
chomp $_;
my ($a, $b, $c, $d) =unpack("A4 A4 A4 A8", $_);
print $a . "\t" . $b . "\t" . $c . "\t" . $d . "\n";
}

Output:
bash-2.05$ ./try-unpack.pl
2008 0331 EJUS D00 0003
2008 0331 SUS D0000 87
2008 0331 XZUS D00000 0
200 0331 XZUS D0000000
20 0331 XZUS D0000000

====================================================================
Script Name: try-pack.pl

#!/usr/bin/perl

use warnings;
use strict;

my $xline;
die " Not enough user specified inputs : $! \n" unless @ARGV == 4;
$xline = pack("A5 A4 A3 A2", $ARGV[0], $ARGV[1], $ARGV[2], $ARGV[3]);
print $xline . "\n";
$xline = pack("a5 a4 a3 a2", $ARGV[0], $ARGV[1], $ARGV[2], $ARGV[3]);
print $xline . "\n";

Output:
bash-2.05$ ./try-pack.pl KUMAR PRA RA BROTHER
KUMARPRA RA BR
KUMARPRARABR

Super Good Article about Veritas Volume Manager

2008-02-21T00:16:00.001-05:00

http://www.adminschoice.com/docs/vxvm.htm

Solaris - Types of file systems

2008-02-20T23:36:00.001-05:00

Conceptually there are only 3 types of file systems:

1. Disk based file system
2. Network based file system
3. Virtual File systems.

Solaris - How to find out, How many partitions exists on a disk

2008-02-20T23:21:00.002-05:00

Use a command called

prtvtoc

df only shows the slices that contains file systems and have been mounted. If we want to see all the partitions on a disk, we can use the 'prtvtoc' command.

~Cheers

हाउ टू तुर्ण ओं फ्लाश्बैक फेअतुरे ओं Oracle

2008-02-20T15:38:00.000-05:00

alter database flashback on;

Test Your Knowledge of Regular Expressions and Shell Basics

2008-02-14T14:32:00.001-05:00

Test Your Knowledge of Regular Expressions and Shell Basics
by Emmett Dulaney

Regular expressions have set Unix-based operating systems apart from others almost since the very beginning. While other operating systems incorporate wild cards and quit there, Unix goes far beyond that. Regular expressions allow you to tweak and refine operations with tools ranging from directory searches to stream editing and everything in between. Not only do you need to know regular expressions, but you have to know some basics about the shell as well a few key commands in order to work with them. Following are 50 questions on regular expressions and shell basics at a knowledge level required for almost any intermediate-level certification exam. Good luck (answers are at the end of the article)!

1. Which of the following characters used to match any single character?

A. a dash (-)
B. an asterisk (*)
C. a question mark (?)
D. a period (.)

2. Which of the following characters is used to signify the beginning of a line?

A. %
B. $
C. ^
D. ~

3. You want to use the question mark character (?) in a regular expression search and not have it interpreted as a metacharacter. Which of the following should be used to accomplish this?

A. "\?"
B. "/?"
C. "$?"
D. "(?)"

4. How many occurrences of a character preceding an asterisk (*) must be present before it is considered a match?

A. zero
B. one
C. two
D. more than two

5. You want to find every line in a file that contains a number. Which of the following regular expressions will accomplish this?

A. -n
B. "0 1 2 3 4 5 6 7 8 9"
C. [0-9]
D. [^0-9]

6. You want to find all occurrences of "Muncie" in a file and suspect that sometimes it may appear initial-capped and other times all in lowercase. Which regular expression should you use to accomplish this?

A. [Muncie,muncie]
B. [Mm]uncie
C. -i muncie
D. {Muncie,muncie}

7. What regular expression should be used to find all lines that begin with a question mark? (Fill in the blank.)

8. Which character is used to mean that the preceding must be matched one or more times?

A. +
B. ?
C. &
D. @

9. You want to find all matches for two distinctly different values. Which character is used to signify that you want to match two values?

A. back slash (\)
B. forward slash (/)
C. pipe (|)
D. ampersand (&)

10.Which of the following should be used to find "Sam" and "Samantha" in a file?

A. Sam(antha)*
B. Sam[antaha]
C. Sam|antha
D. Sam$antha$\?

11. Which of the following can be used to find any white space, including spaces and tabs?

A. [white]
B. ""
C. [[:space:]]
D. [[tab|space]]

12. Which of the following characters is used to signify the end of a line?

A. %
B. $
C. ^
D. ~

13. What set of characters will be matched if the expression is [1-9A-D]?

A. 123456789ABCDabcd
B. 123456789ABCD
C. 19ADad
D. 19AD

14. Which of the following matches will be found to file\.html? (choose all that apply):
A. file.htmlll
B. file.html
C. file.htm
D. file

15. Which of the following regular expressions should be used to find lines that do not contain numbers?
A. -n
B. "\0 \1 \2 \3 \4 \5 \6 \7 \8 \9"
C. [0-9]
D. [^0-9]

16. On the command line, what does encompassing a string within single quotes accomplish?

A. It turns off the special significance of everything within the quotes.
B. It turns off the special significance of everything within the quotes except for a few very special characters.
C. It executes the command within.
D. It sets a variable value.

17. You want to perform a test on a string to make sure that the length of it is not zero before using it. Which test should be done to accomplish this?

A. [[ string ]]
B. [[ -z string ]]
C. [[ -n string ]]
D. [[ -a string ]]

18. You are writing a shell script that includes a number of choices within a case statement. What is used to end the case statement?

A. done
B. fi
C. end
D. esac

19. Which of the following can be checked to see how many positional parameters were used to call a script?

A. $#
B. $$
C. $!
D. $?

20. Which switch should be used with grep to print all lines in a file that do not match the search criteria given?

A. -i
B. -v
C. -c
D. -n

21. You are writing a simple shell script that will prompt the user and require them to enter a string variable. What command will you need to use within the script to input the user's string?

A. input
B. enter
C. read
D. record

22. What is the stream number associated with standard error?

A. 3
B. 2
C. 1
D. 0

23. Which of the following regular expressions would indicate that the search item preceding it must be found at least 5 times?

A. (5)
B. 5x
C. {5,}
D. [5+]

24. Which of the following should be used to test if two strings are equal?

A. string1 = string2
B. string1 –eq string2
C. string1 –a string2
D. string1 –o string2

25. Which of the following would be the result of the command echo 1{2,3,4}5 (choose all that apply)?

A. 15
B. 125
C. 135
D. 145
E. 12345
F. 12,3,45
G. 1{2,3,4}5

26. On the command line, what does encompassing a string within double quotes accomplish?

A. It turns off the special significance of everything within the quotes.
B. It turns off the special significance of everything within the quotes except for a few very special characters.
C. It executes the command within.
D. It sets a variable value.

27. Which of the following can be used to see the arguments given when the shell script was invoked?

A. $#
B. $?
C. $0
D. $*

28. You are including a while loop in a shell script. What is used to end the while loop?

A. done
B. fi
C. end
D. esac

29. What regular expression can be used to find all lines that end with a period? (Fill in the blank.)

30. Which switch should be used with grep to ignore case as you look for matches in a file?

A. -i
B. -v
C. -c
D. -n

31. Which of the following is a synonym for [^[:alnum:]] ?

A. \W
B. \w
C. \a
D. \A

32. Within the Bash shell, what is the tilde (~) translated to by default?

A. the PATH
B. the present working directory
C. the user's home directory
D. the TMP directory

33. With a simple command given at a prompt, how does Bash process it?

A. from right to left
B. from left to right
C. in alphabetic order
D. in ASCII order

34. Which of the following Bash built-in commands can be used within a shell script to parse positional variables?

A. shear
B. parse
C. trim
D. getopts

35. The typeset command exists in Bash for compatibility with Korn shell scripts. What command, however, is more favored for use with Bash?

A. slot
B. state
C. declare
D. proclaim

36. On the command line, what does encompassing a string within backticks accomplish?

A. It turns off the special significance of everything within the backticks.
B. It turns off the special significance of everything within the backticks except for a few very special characters.
C. It executes the command within.
D. It sets a variable value.

37. Which of the following can be used within a shell script to see the name with which the shell is being executed?

A. $#
B. $?
C. $0
D. $*

38. You are tweaking a shell script by adding an until loop. What needs to be used to end the until loop?

A. done
B. fi
C. end
D. esac

39. Which of the following should be used to test if the value of two integers is the same?

A. integer1 = integer2
B. integer1 –eq integer2
C. integer1 –a integer2
D. integer1 –o integer2

40. Which switch should be used with grep to count all lines in a file that match the search criteria?

A. -i
B. -v
C. -c
D. -n

41. What is the file descriptor/stream number for standard input? (Fill in the blank.)

42. Which of the following utilities processes most quickly?

A. grep
B. egrep
C. fgrep

43. Which of the following regular expressions means the search criteria preceding it must be found at least seven times, but not more than ten times?

A. {7,,10}
B. {7,10}
C. {7>10}
D. {7,!10}

44. Which of the following regular expressions can be used to find all blank lines in a file?

A.""
B. ^$
C. ^" "$
D. [ ]

45. In a shell script, you have nested one loop within another (both using the syntax for – do – done). What can be used to exit the first loop without exiting the second once a specific condition is met?

A. enod
B. end
C. break
D. rof

46. Which option can be used with test to see if a file exists and is a regular file?

A. -r
B. -e
C. -a
D. -f

47. What is the stream number associated with standard output?

A. 3
B. 2
C. 1
D. 0

48. Which of the following can be used to see the exit code of the last command or shell executed?

A. $#
B. $?
C. $0
D. $*

49. Which test on a string can be used to make sure that the length of it is zero?

A. [[ string ]]
B. [[ -z string ]]
C. [[ -n string ]]
D. [[ -a string ]]

50. If the value of ALT is set to the string "MPC", what will the command echo '$ALT' return?

A. $MPC
B. MPC
C. ALT
D. $ALT

Answers

1. A period (.) is used to match any single character. Answer: D.

2. The circumflex (^) is used to signify the beginning of a line. Answer: C.

3. You must use the backslash (\) with the metacharacter – "\?". Answer: A.

4. The asterisk (*) will match zero or more occurrences of the character(s) preceding it. Answer: A.

5. The expression [0-9] will find a match for any number between 0 and 9 (all numbers). Answer: C.

6. The expression [Mm]uncie will find both "Muncie" and "muncie" . Answer: B.

7. The regular expression to use is : ^\?

8. The plus sign (+) is used to indicate that the preceding must be matched one or more times. Answer: A.

9. A pipe (|) is used to separate multiple values being searched for. Answer: C.

10. Using the expression Sam$antha$\? will always match "Sam" and it can be followed by zero or one (?) occurrences of "antha" . Answer: D.

11. The expression [[:space:]] can be used to find any white space, including spaces and tabs. Answer: C.

12. The dollar sign ($) is used to signify the end of a line. Answer: B.

13. Anything within the character set 123456789ABCD will be matched the expression [1-9A-D]. Answer: B.

14. The question mark (?) will match zero or one occurrence of the "l", meaning that both file.htm and file.html will be found. Answer: B&C.

15. The expression [^0-9] will find a match to everything except the number set 0 to 9. Answer: D.

16. Single quotes are used to turn off the special significance of everything within the quotes. Answer: A.

17. The syntax [[ -n string ]] is used to see if the string has a length greater than zero. Answer: C.

18. The case statement ends with esac. Answer: D.

19. The value of $# can be checked to see how many positional parameters were used to call a script. Answer: A.

20. The –v switch is used to print all lines of a file that do not match the search criteria given. Answer: B.

21. The read command is used to accept a value and assign it to a variable. Answer: C.

22. Standard error is stream 2. Answer: B.

23. The expression {5,} means the preceding must be found at least five times. Answer: C.

24. To test and see if two string values are the same, the equal sign (=) is used. Answer: A.

25. The command will echo "1" and "5" with each number specified between the braces in the middle: 125, 135, and 145. Answer: B&C&D.

26. Double quotes turn off the special significance of everything within the quotes except for a few very special characters that remain (such as single quotes, the dollar sign, and back slash). Answer: B.

27. The variable $* can be used to see the arguments given when the shell script was invoked. Answer: D.

28. A while loop ends with done (while – do – done). Answer: A.

29. The regular expression to use is: \.$

30. The –i option is used to ignore case. Answer: A.

31. \W is a synonym for [^[:alnum:]]. Answer: A.

32. The tilde, by default, translates to the home directory of the user. Answer: C.

33. Simple commands are executed from left to right. Answer: B.

34. The command getopts is a Bash built-in that can be used within a shell script to parse positional variables. Answer: D.

35. The declare command is used to proclaim what type of variable it is so it can be handled accordingly. Answer: C.

36. A command can be placed within backticks and that command is then executed, with the value of execution becoming the resulting string/value. Answer: C.

37. The positional variable $0 holds the name with which the script was summoned. Answer: C.

38. An until loop ends with done (until – do – done). Answer: A.

39. A test can be done to see if the values of two integers are the same using the –eq parameter. Answer: B.

40. The –c switch is used to count lines that match the search criteria. Answer: C.

41. The file descriptor/stream number for standard input is 0.

42. The fgrep utility does not have the same regular expression set as the other two, and is thus able to execute the fastest. Answer: C.

43. The regular expressions {7,10} means the search criteria preceding it must be found at least seven times, but not more than ten times. Answer: B.

44. To find the blank lines, look for the beginning (^) and end ($) with nothing between them (^$). Answer: B.

45. The break statement can be used to exit a nested loop. Answer: C.

46. The –f option is used to see if a file exists and is a regular file. Answer: D.

47. Standard output is stream 1. Answer: C.

48. The value of $? is equal to the exit code returned by the last command executed. Answer: B.

49. The test [[ -z string ]] will verify that the length of the string is zero. Answer: B.50. Because the single quotes override the special meaning of the dollar sign,the string give ($ALT) is literally returned. Answer: D.

50. The original Ethernet standard, first published in 1980 by the consortium of DEC, Intel, and Xerox, specified a speed of 10 Mbps. Answer: C.

Emmett Dulaney is the author of the several books on Linux/Unix and certification as well as a columnist for UnixReview.com. Emmett's blog can be found at: http://edulaney.blogspot.com, and he can be reached (and welcomes your comments) at: edulaney@insightbb.com.

Test Your Knowledge of Users and Groups by Emmett Dulaney :

2008-02-14T14:22:00.000-05:00

Test Your Knowledge of Users and Groups by Emmett Dulaney :

If there is one thing that all administrators deal with on a regular basis, it is users and groups. If there is
one topic that you should know inside and out, it is users and groups.
That said, following are 50 questions
intended to test your knowledge of user and group fundamentals at an intermediate level.

Good luck (answers are at the end of the article)!

1. What is the default UID number assigned to the first user added to a system on most systems?

A. 1
B. 100
C. 1000
D. 10000

2. Which command can be used at the command line to change your active GID to a new one?

A. chgroup
B. group
C. newgrp
D. switch

3. Which field of the /etc/passwd file identifies the user’s primary group ID?

A. 1
B. 3
C. 4
D. 5
E. 6
F. 7

4. NIS entries are automatically added to your system. What character precedes entries in /etc/passwd for which
this is done?

A. +
B. !
C. ?
D. %

5. How many fields does the /etc/shadow file consist of?

A. 7
B. 9
C. 12
D. 15

6. Which command can be used to see a user’s password aging information?

A. useradd -l
B. passwd -l
C. chage -l
D. usermod -l

7. If the passwords are stored in /etc/shadow instead of /etc/passwd, what single letter is found in the second column
of /etc/passwd entries? __________ (Fill in the blank.)

8. Who owns the /etc/group file?

A. root
B. bin
C. daemon
D. nobody

9. Which tool can be used to create a user account with default values?

A. pwck
B. useradd
C. usermod
D. chfn

10. Which module can PAM use to enforce strong passwords (choose the best answer)?

A. pam_strong
B. pam_usersec
C. pam_pwcheck
D. pam_cracker

11. Instead of logging in as root regularly, you have advised all administrators to use sudo. Which files logs
all sudo commands?

A. /tmp/sudo/log
B. /var/sudolog
C. /etc/sudo/log
D. /var/log/messages

12. The root user, on every system, always has the same UID. What is its value?

A. 0
B. 1
C. 10
D. 100

13. Within the member list field of the /etc/group file, what character is used to separate members?

A. a colon (:)
B. a comma (,)
C. a period (.)
D. a pipe (|)

14. By default, what utility is used to hash the passwords that appear in /etc/shadow?

A. hash
B. encode
C. pgp
D. crypt

15. Which file can be used to limit which users can use sudo?

A. /etc/sudo
B. /etc/sudoers
C. /etc/sudo/accept
D. /etc/accept

16. In Ubuntu, which utility can be used to add a new user to the system?

A. makeuser
B. newuser
C. adduser
D. usermake

17. Which command is used to change an NIS user’s password?

A. nispasswd
B. yppasswd
C. passwd -nis
D. gpasswd

18. How many fields are there in the /etc/group file?

A. 4
B. 5
C. 6
D. 7

19. Which field of the /etc/passwd file identifies the home directory for the user?

A. 1
B. 3
C. 4
D. 5
E. 6
F. 7

20. If you want to run su and not only become the other user, but also run their login shell, which option should
you specify?

A. -
B. -l
C. -r
D. -s

21. What character is used as a delimiter between fields in the /etc/passwd file? __________ (Fill in the blank.)

22. In the /etc/shadow file, dates are specified for when the password was set/changed and the absolute last date
that it can be used. This is expressed as a number of days since when?

A. January 1, 1970
B. December 31, 1969
C. December 25, 1968
D. November 30, 1967

23. Which PAM module examines the home directory of the user for files/directories that have dangerous permissions and
issues a warning if there are any there?

A. pam_env.so
B. pam_homecheck.so
C. pam_securetty.so
D. pam_unix2.so

24. In the following /etc/shadow entry, which value indicates the number of days after a password has expired that
the account is disabled and cannot be used?

edulaney:PcaQWn6d1la5.:13000:0:1:2:3:14000:

A. 0
B. 1
C. 2
D. 3

25. Which field of the /etc/passwd file holds the UID?

A. 1
B. 3
C. 4
D. 5
E. 6
F. 7

26. What is the default GID number assigned to the first group added to a system on most systems?

A. 1
B. 100
C. 1000
D. 10000

27. Which command can be used to add a new user to an existing group?

A. groupadd -g
B. groupmod -g
C. useradd -g
D. usermod -g

28. For security reasons, you want to prevent the use of finger and the values that are returned to it from /etc/passwd. Which port should be blocked at the firewall?

A. 49
B. 59
C. 69
D. 79

29. What character should be added to an account entry to disable it? __________ (Fill in the blank.)

30. Which command can be used to add an existing user to an existing group?

A. groupadd -g
B. groupmod -g
C. useradd -g
D. usermod -g

31. If you want to run su and not only become root, but also use root’s environmental variables. Which option should you specify?

A. -
B.-c
C. -r
D. -s

32. Which of the following files holds the default password aging information for newly created accounts?

A. /etc/inittab
B. /etc/defaults/passwd
C. /etc/defaults/aging
D. /etc/login.defs

33. Which PAM module verifies that the username name given is valid (exists in passwd and shadow)?

A. pam_env.so
B. pam_homecheck.so
C. pam_securetty.so
D. pam_unix2.so

34. Which field of the /etc/passwd file identifies the default shell to use when the user logs in?

A. 1
B. 3
C. 4
D. 5
E. 6
F. 7

35. In the following /etc/shadow entry, which value indicates the maximum number of days the password can be used before it must be changed?

edulaney:PcaQWn6d1la5.:13000:0:1:2:3:14000:

A. 0
B. 1
C. 2
D. 3

36. Which command is used to convert passwords from /etc/password entries into /etc/shadow entries?

A. pwconv
B. pwunconv
C. convert
D. unshadow

37. The root user, on every system, always has the same group ID (GID) value. What is that value?

A. 0
B. 1
C.10
D. 100

38. Which tool can be used to change CGOS values?

A.pwck
B. useradd
C. usermod
D. chfn

39. Which command is used to change an LDAP password?

A. passwdldap
B. lpasswd
C. ldappaswd
D. yp

40. Which of the following system accounts has a default GID of 1?

A. bin
B. mail
C. uucp
D. named

41. Which field of the /etc/passwd file holds the login name?

A. 1
B. 3
C. 4
D. 5
E. 6
F. 7

42. Which of the following files holds default values assigned to newly created user accounts?

A. /etc/default/useradd
B. /etc/users/default
C. /etc/useradd/users
D. /etc/default

43. Which command-line utility can be used in Ubuntu to remove a group?

A. ungroup
B. group_rm
C. rmgroup
D. delgroup

44. Within which directory does su reside by default?

A. /bin
B. /etc
C. /usr
D. /var

45. Which PAM module verifies that the root user is allowed access from the current terminal?

A. pam_env.so
B. pam_homecheck.so
C. pam_securetty.so
D. pam_unix2.so

46. In the following /etc/shadow entry, which value indicates the minimum number of days the password has to be used
before it can be changed?

edulaney:PcaQWn6d1la5.:13000:0:1:2:3:14000:

A. 0
B. 1
C. 2
D. 3

47. Which tool can be used to check the integrity of the passwd and shadow files?

A. pwck
B. useradd
C. usermod
D. chfn

48. Which command is used to convert passwords from /etc/shadow entries into /etc/passwd entries?

A. arsort()
B. rev()
C. trosa()
D. zsort()

49. Which field of the /etc/passwd file is known as the GCOS field?

A. 1
B. 3
C. 4
D. 5
E. 6
F. 7

50. Which of the following system accounts has a default UID of 10?

A. bin
B. mail
C. uucp
D. named

Answers

1. The default user ID number on most systems is 1000, and the numbers then increment by one from there with each newly
added user. Answer: C.

2. The newgrp command can be used at the command line to change your active GID to a new one.
Answer: C.

3. The fourth field of /etc/passwd identifies the GID.
Answer: C.

4. The plus sign (“+”) precedes entries in /etc/passwd for which NIS inserts values. Answer: A.

5. There are nine fields in the /etc/shadow file.
Answer: B.

6. The chage –l command can be used to see a user’s password aging information (for example, chage –l edulaney).
Answer: C.

7. An “x” in the second column of /etc/passwd indicates that the password values are being stored in /etc/shadow.

8. The root user, by default, owns the /etc/group file.
Answer: A.

9. The useradd tool can be used to create a user account with default values.
Answer: B.

10. PAM can use the pam_pwcheck module to enforce strong passwords.
Answer: C.

11. The /var/log/messages file logs all sudo commands.
Answer: D.

12. The UID number for root is always 0.
Answer: A.

13. Within the member list field of the /etc/group file, a comma is used to separate members.
Answer: B.

14. The crypt utility is used to hash the passwords that appear in /etc/shadow.
Answer: D.

15. The /etc/sudoers file can be used to limit which users can use sudo.
Answer: B.

16. The adduser utility can be used to add a new user to the system.
Answer: C.

17. The yppasswd command is used to change an NIS user’s password.
Answer: B.

18. The /etc/group file consists of four fields.
Answer: A.

19. The sixth field of /etc/passwd identifies the user’s home directory.
Answer: E.

20. To run su and not only become the other user, but also run their login shell, specify the -l (login) option.
Answer: B.

21. Answer: The colon (“:”) is used as a delimiter between fields in the /etc/passwd file.

22. Values are expressed as the number of days since January 1, 1970.
Answer: A.

23. The pam_homecheck.so module performs this function.
Answer: B.

24. The seventh field of an /etc/shadow entry – holding a “3” in this case – indicates the number of days after the
password expires before the account is disabled.
Answer: D.

25. The third field of /etc/passwd holds the UID.
Answer: B.

26. The first group added to most systems begins at 100 and increments from there with each newly added group.
Answer: B.

27. The useradd –g command can be used to add a new user to an existing group.
Answer: C.

28. The finger port to block is 79.
Answer: D.

29. Answer: An asterisk (“*”) character should be added to an account entry to disable it.

30. The usermod –g command can be used to add an existing user to an existing group.
Answer: D.

31. Using just the dash (su -), you not only become root, but also use root’s environmental variables.
Answer: A.

32. The /etc/login.defs file holds the default password aging information for newly created accounts.
Answer: D.

33. The pam_unix2.so module performs this function.
Answer: D.

34. The seventh field holds the login shell path. If no value is given, the default shell is assigned.
Answer: F.

35. The fifth field of an /etc/shadow entry – holding a “1” in this case – indicates the maximum number of days the
password can be used before it must be changed.
Answer: B.

36. The pwconv command is used to convert passwords from /etc/password entries into /etc/shadow entries.
Answer: A.

37. The primary GID number for root is 0.
Answer: A.

38. The chfn tool can be used to change CGOS values.
Answer: D.

39. The ldappaswd utility is used to change an LDAP password.
Answer: C.

40. By default, the bin account has a UID and GID of 1.
Answer: A.

41. The first field holds the login name.
Answer: A.

42. The /etc/default/useradd file holds default values assigned to newly created user accounts.
Answer: A.

43. The delgroup command-line utility can be used in Ubuntu to remove a group.
Answer: D.

44. The su utility resides beneath /bin.
Answer: A.

45. The pam_securetty.so module performs this function.
Answer: C.

46. The fourth field of an /etc/shadow entry – holding a “0” in this case – indicates the minimum number of days the
password has to be used before it can be changed.
Answer: A.

47. The pwck tool can be used to check the integrity of the passwd and shadow files.
Answer: A.

48. The pwunconv command is used to convert passwords from /etc/shadow entries into /etc/passwd entries.
Answer: B.

49. The fifth field is the GCOS (General Electric Comprehensive Operating System) field. It holds free text that is
identifies the user and is often used to return values with finger.
Answer: D.

50. By default, the special account uucp has the UID of 10. Answer: C.

Emmett Dulaney is the author of the several books on Linux/Unix and certification as well as a columnist for UnixReview.
Emmett’s blog can be found at http://edulaney.blogspot.com and he can be reached
(and welcomes your comments) at edulaney@insightbb.com.

http://www.kalamazoolinux.org/tech/find.html

2008-02-14T13:18:00.000-05:00

http://www.kalamazoolinux.org/tech/find.html

(Status ऑफ़ एकाच सोलारिस प्रोसस्सर ) psrinfo -v

2008-02-07T16:40:00.000-05:00

Status of virtual processor 0 as of: 02/07/2008 16:40:50
on-line since 01/19/2008 05:39:05.
The sparcv9 processor operates at 900 MHz,
and has a sparcv9 floating point processor.
Status of virtual processor 1 as of: 02/07/2008 16:40:50
on-line since 01/19/2008 05:39:05.
The sparcv9 processor operates at 900 MHz,
and has a sparcv9 floating point processor.
Status of virtual processor 2 as of: 02/07/2008 16:40:50
on-line since 01/19/2008 05:39:05.
The sparcv9 processor operates at 900 MHz,
and has a sparcv9 floating point processor.
Status of virtual processor 3 as of: 02/07/2008 16:40:50
on-line since 01/19/2008 05:39:04.
The sparcv9 processor operates at 900 MHz,
and has a sparcv9 floating point processor.

What does “> /dev/null 2>&1″ mean?

2008-02-05T13:11:00.000-05:00

What does “> /dev/null 2>&1″ mean?

./Script.sh > /dev/null 2>&1Output redirection
The greater-thans (>) in commands like these redirect the program’s
outputsomewhere. In this case, something is being redirected into /dev/null, and
something is being redirected into &1.

Standard in, out, and error
There are three standard sources of input and output for a program. Standard input usually comes from the keyboard if it’s an interactive program, or from
another program if it’s processing the other program’s output. The program usually prints to standard output, and sometimes prints to standard error. These three
file descriptors (you can think of them as “data pipes”) are often
called STDIN, STDOUT, and STDERR.

Sometimes they’re not named, they’re numbered! The built-in numberings for them
are 0, 1, and 2, in that order. By default, if you don’t name or number one explicitly, you’re talking about STDOUT.

Given that context, you can see the command above is redirecting standard output into /dev/null, which is a place you can dump anything you don’t want (often called the bit-bucket), then redirecting standard error into standard output (you have to put an & in front of the destination when you do this).

The short explanation, therefore, is “all output from this command should be shoved into a black hole.” That’s one good way to make a program be really quiet.

/dev/null

2008-02-05T12:09:00.001-05:00

http://en.wikipedia.org/wiki/Data_sink

कोड to display, How can arguments be passed to a function in K SHELL script.

2008-02-05T10:52:00.000-05:00

#!/usr/bin/ksh

## Code to display, How can arguments be passed to a function in K SHELL script.
## First $1 is the first input to this script. See below for passing on parameters to
## the functionA.
##
## Status: Tested.

xx=$1
yy=$1/logs/script.log

functionA()
{
a=$1
b=$2

echo $a
echo $b
}

functionA "Deepak" "Ranjan"
functionA $xx $yy

http://en.wikiversity.org/wiki/User:Roadrunner

2008-02-02T01:22:00.000-05:00

Folks interested in Financial Engineering/Quants/Trading algorithm development:

I was just Google'ing around on the subject and hit upon an interesting site:
http://en.wikiversity.org/wiki/User:Roadrunner

This seems to be owned by Joseph Wang, an Astrophysicist but works in Financial Engineering industry. Check this site out. Good for starters.....

DBI.pm utilities - It is just a ctrl-c & ctrl-v

2008-01-30T13:32:00.000-05:00

BEGIN {
$DBI::VERSION = "1.59"; # ==> ALSO update the version in the pod text below!
}

=head1 NAME

DBI - Database independent interface for Perl

=head1 SYNOPSIS

use DBI;

@driver_names = DBI->available_drivers;
%drivers = DBI->installed_drivers;
@data_sources = DBI->data_sources($driver_name, \%attr);

$dbh = DBI->connect($data_source, $username, $auth, \%attr);

$rv = $dbh->do($statement);
$rv = $dbh->do($statement, \%attr);
$rv = $dbh->do($statement, \%attr, @bind_values);

$ary_ref = $dbh->selectall_arrayref($statement);
$hash_ref = $dbh->selectall_hashref($statement, $key_field);

$ary_ref = $dbh->selectcol_arrayref($statement);
$ary_ref = $dbh->selectcol_arrayref($statement, \%attr);

@row_ary = $dbh->selectrow_array($statement);
$ary_ref = $dbh->selectrow_arrayref($statement);
$hash_ref = $dbh->selectrow_hashref($statement);

$sth = $dbh->prepare($statement);
$sth = $dbh->prepare_cached($statement);

$rc = $sth->bind_param($p_num, $bind_value);
$rc = $sth->bind_param($p_num, $bind_value, $bind_type);
$rc = $sth->bind_param($p_num, $bind_value, \%attr);

$rv = $sth->execute;
$rv = $sth->execute(@bind_values);
$rv = $sth->execute_array(\%attr, ...);

$rc = $sth->bind_col($col_num, \$col_variable);
$rc = $sth->bind_columns(@list_of_refs_to_vars_to_bind);

@row_ary = $sth->fetchrow_array;
$ary_ref = $sth->fetchrow_arrayref;
$hash_ref = $sth->fetchrow_hashref;

$ary_ref = $sth->fetchall_arrayref;
$ary_ref = $sth->fetchall_arrayref( $slice, $max_rows );

$hash_ref = $sth->fetchall_hashref( $key_field );

$rv = $sth->rows;

$rc = $dbh->begin_work;
$rc = $dbh->commit;
$rc = $dbh->rollback;

$quoted_string = $dbh->quote($string);

$rc = $h->err;
$str = $h->errstr;
$rv = $h->state;

$rc = $dbh->disconnect;

Standard DBD in PERL installation - We can implement ours too.

2008-01-30T13:18:00.000-05:00

DBD::Adabas
DBD::ADO
DBD::Amazon
DBD::AnyData
DBD::ASAny
DBD::Chart
DBD::CSV
DBD::DB2
DBD::DBMaker
DBD::DBM
DBD::EmpressNet
DBD::Empress
DBD::ExampleP
DBD::Excel
DBD::File
DBD::Fulcrum
DBD::Gofer
DBD::Google
DBD::Illustra
DBD::Informix4
DBD::Informix
DBD::Ingres
DBD::InterBase
DBD::iPod
DBD::JDBC
DBD::LDAP
DBD::Log
DBD::MaxDB
DBD::Mimer
DBD::Mock
DBD::monetdb
DBD::mSQL
DBD::Multiplex
DBD::Multi
DBD::mysqlPP
DBD::mysql
DBD::NullP
DBD::ODBC
DBD::Oracle
DBD::Ovrimos
DBD::PgLite
DBD::PgPP
DBD::PgSPI
DBD::Pg
DBD::pNET
DBD::PrimeBase
DBD::Proxy
DBD::QBase
DBD::RAM
DBD::RDFStore
DBD::Recall
DBD::Redbase
DBD::Salesforce
DBD::SearchServer
DBD::Solid
DBD::Sponge
DBD::Sprite
DBD::Sqlflex
DBD::SQLite2
DBD::SQLite
DBD::Sybase
DBD::TemplateSS
DBD::Template
DBD::Teradata
DBD::TimesTen
DBD::TSM
DBD::Unify
DBD::WMI
DBD::WTSprite
DBD::XBase
DBD::Yaswi

Perl DBI Master Key Site

2008-01-30T13:17:00.001-05:00

http://dbi.tiddlyspot.com/

This has most of the thing an experianced people using DBI need to know.

K-Shell programming

2008-01-30T11:45:00.001-05:00

Very good site for ksh programming learning:

http://www.bolthole.com/solaris/ksh.html

Happy Learning.

Different compression techniques

2008-01-29T20:05:00.000-05:00

http://en.wikipedia.org/wiki/Bzip2
http://en.wikipedia.org/wiki/Gunzip ( same as gzip)
http://en.wikipedia.org/wiki/Compress

Good read - gzip -

2008-01-29T20:04:00.000-05:00

Good study article about gzip (GNU zip).

http://en.wikipedia.org/wiki/Gzip

Open Group Base Specifications (Owner of UNIX & POSIX)

2008-01-29T16:25:00.000-05:00

Folks,

If you have any question regarding UNIX or UNIX like system aka POSIX standard and stuff, you can go to :

http://www.opengroup.org/

Brain Bench Perl 5.8 Certification

2008-01-25T23:49:00.000-05:00

Folks,

I got certified in Perl 5.8 today and will be getting my certification in couple of days. It really has some good questions, worth taking a look at this exam.

-Deepak

Perl Tricks

2008-01-24T15:14:00.000-05:00

Quote and Quote-like Operators ------------------------------While we usually think of quotes as literal values, in Perl theyfunction as operators, providing various kinds of interpolating and pattern matching capabilities. Perl provides customary quote characters for these behaviors, but also provides a way for you to choose your quote character for any of them. In the following table, a {} represents any pair of delimiters you choose.

Customary Generic Meaning Interpolates
'' q{} Literal no
"" qq{} Literal yes
`` qx{} Command yes
* qw{} Word list no
// m{} Pattern match yes
* qr{} Pattern yes
* s{}{} Substitution yes
* tr{}{} Transliteration no (but see below
'<<'EOF here-doc yes

* * unless the delimiter is ''.

Perl Quiz Series - Part I

2008-01-24T10:58:00.000-05:00

Perl Questions:

Generic Questions:
1. What is 'our' used for ?
e.g our($VERSION, @ISA, @EXPORT, @EXPORT_OK, %EXPORT_TAGS)
2. What is 'exists' function used for?
3. What is 'uc' function used for ?
4. What is 'ref' function used for ?
5. What is 'defined' function used for ?
6. What is 'map' function used for ?
7. What is 'reverse' function used for ?
8. What is ' qq qw ' used for ?
9. What is 'tr' function used for ?
10. What is 'tie' function used for ?
11. What is ' push & pop ' function used for ?
12. What is ' undef ' function used for ?
13. What is ' bless ' function used for ?
14. What is ' self ' function used for ?
15. What is ' __FILE__ ' variable used for ?
16. What is ' __LINE__ ' variable used for ?
17. What is ' $_ ' used for ?
18. What is ' @_ ' used for ?
19. What is ' $$ ' used for ?
20. What is ' shift ' function used for ?
21. What is ' unless ' function used for ?
22. What is ' self ' function used for ?
23. What is ' untie ' function used for ?
24. What is 'split' function used for ?
25. What is 'splice' function used for ?
26. What is 'sort' function used for ?
27. What is 'keys' function used for ?
28. What is 'values' function used for ?
29. How to dereference a array reference $ref_a ? ( @$ref_a )
30. How to dereference a hash reference $ref_h ? ( %$ref_h )
31. How to dereference a scalar reference $ref_s ? ( $$ref_s )
32. What is difference between 'for & foreach' loop ?
33. What is 'while' function used for ?
34. What is 'last' function used for ?
35. What is 'exit' function used for ?
36. What is difference between 'die & warn' ?
37. What is 'eval' function used for ?
38. What is '$@' variable used for ?
39. What is 'Here document' ?
40. What is difference between 'exec & system' function?
41. How to set environment variable in perl ? ( $ENV{xx} )
42. What is ' $ ' (dollar pipe) used for ?
43. What is 'shebang'? ( #! ) --> first line of perl code
44. Can we use ' -w ' switch on first line OR 'use warnings' module alternatively ?
45. What is the difference between 'chomp & chop'?
46. How to invoke a unix shell command inside a perl script ? ( `ls -l` )
47. What is the difference between 'use & require' ?
48. What is '@ARGV' used for ? (Number of arguments)
49. What is ' . ' ( dot operator ) used for ?

Use google search engine from command line.

2008-01-23T16:01:00.000-05:00

#!/usr/bin/perl -w

my $browser = "/usr/bin/mozilla-firefox";
exec $browser, "http://www.google.com/advanced_search" unless @ARGV;

for ( @ARGV )
{
s/.*/%22$&%22/ if y/ /+/; $s .= $s?"+$_":"$_";
}

exec $browser, "http://www.google.com/search?num=30&hl=en&as_qdr=all&q=$s&btnG=Google+Search"

Comparison of file systems - Wikipedia, the free encyclopedia

2008-01-15T13:04:00.000-05:00

Truly awesome stuff from Wikipedia.org

Comparison of file systems - Wikipedia, the free encyclopedia

can I use $match within regex , sun as / $match ../

2008-01-11T16:26:00.000-05:00

Building a pattern at run-time by interpolating a variable into a pattern. Yes, you can interpolate a variable such as $match into a pattern; you'll generally want the qr// operator to quote the pieces you use to make $match.

http://perldoc.perl.org/perlop.html#Regexp-Quote-Like-Operators