Linux Shell Scripts

Shell Scripts - Part 09

2007-04-02T19:46:00.000+05:30

Shell Scripts - Part 09

091-contactus.cgi
To process the contact us form data, email it to the designated recipient, and return a succinct thank you message.

092-contactus.html
A html helper file for script #91, contactus.cgi

093-photoalbum.cgi
A dynamic web photo album utility.

094-guestbook.cgi
To display the current guestbook entries, append a simple form for visitors to add their own comments, and accept and process new guest entries. Works with a separate data file that actually contains the guest data.

095-guestbook.txt
Data file for script #94, guestbook.cgi

096-counter.sh
A simple text-based page counter, with appropriate locking

097-page-with-counter.html
Html helper file for script #96, counter

098-streamfile.cgi
An output an HTML file, replacing the sequence ---countervalue--- with the current counter value.

099-updatecounter.sh
A tiny script that updates the counter file to the value specified. Assumes that locking is done elsewhere.

0100-randomquote.sh

Given a one-line-per-entry datafile, this script will randomly pick one and display it. Best used as an SSI call within a Web page.

Shell Scripts - Part 08

2007-04-02T19:30:00.000+05:30

Shell Scripts - Part 08

081-exchangerate.sh
Given a currency amount, convert it into other major currencies and show the equivalent amounts in each.

082-getexchrate.sh
To scrape the current currency exchange rates from CNN's money and finance Web site.

083-getstock.sh
given a stock ticker symbol, return its current value from the Lycos web site

084-portfolio.sh
To calculate the value of each stock in your holdings, then calculate the value of your overall portfolio, based on the latest stock market position.

085-changetrack.sh
To track a given URL, and if it's changed since the last visit, email the new page to the specified address.

086-showcgienv.sh
To display the CGI runtime environment, as given to any CGI script on this system.

087-logsearch.cgi
To given a search request, log the pattern, then feed the entire sequence to the real Yahoo search system.

088-yahoo-search.html
html helper file for script #70, logsearch.

089-getdope.sh
To grab the latest column of 'The Straight Dope' and mail it to the specified recipient

090-kevin-and-kell.cgi
Build a Web page on-the-fly to display the latest strip from the cartoon strip Kevin and Kell, by Bill Holbrook (Strip referenced with permission of the cartoonist)

Shell Scripts - Part 07

2007-04-02T19:19:00.001+05:30

Shell Scripts - Part 07

071-backup.sh
To create either a full or incremental backup of a set of defined directories on the system. By default, the output file is saved in /tmp with a timestamped filename, compressed.

072-archivedir.sh
To create a compressed archive of the specified directory.

073-connecttime.sh
Reports cumulative connection time for month/year entries found in the system log file.

074-ftpget.sh
given an ftp: style URL, unwrap it, and try to obtain the file using anonymous ftp.

075-bbcnews.sh
To report the top stories of the BBC World Service.

076-getlinks.sh
given a URL, return all of its internal and external links.

077-define.sh
given a word, return its definition from dictionary.com

078-weather.sh
report weather forecast, including lat/long, for zip

079-checklibrary.sh
log in to the Boulder Public Library computer system and show the due date of everything checked out for the specified user. A demonstration of how to work with the method="post" form with lynx.

080-moviedata.sh
given a movie title, return a list of matches, if there's more than one, or a synopsis of the movie if there's just one. Uses the Internet Movie Database (imdb.com)

Shell Scripts - Part 06

2007-04-02T19:10:00.000+05:30

Shell Scripts - Part 06

061-timein.sh
To show the current time in the specified timezone or geographic zone. Without any argument, show UTC/GMT. Use the word "list" to see a list of known geographic regions Note that it's possible to match a zone directory (a region) but that only timezone files are valid specifications.

062-remember.sh
An easy command-line based memory pad. Search the results with 'remindme'

063-remindme.sh
To search a datafile for matching lines, or show the contents of the datafile if no arg is specified

064-calc.sh
A command-line calculator that acts as a front-end to bc

065-checkspelling.sh
To check the spelling of a word

066-enabled.sh
To show what services are enabled with inetd and xinetd, if they're available on the system.

067-killall.sh
To send the specified signal to all processes that match a specific process name.

068-verifycron.sh
script checks a crontab file to ensure that it's formatted properly. Expects standard cron notation where min is 0-59, hr 0-23, dom is 1-31, mon is 1-12 (or names) and dow is 0-7 (or names). Fields can have ranges (a-e), lists separated by commas (a,c,z), or an asterisk. Note that the step value notation of Vixie cron is not supported (e.g., 2-6/2).

069-docron.sh
A simple script to run the daily, weekly and monthly system cron jobs on a system where it's likely that it'll be shut down at the usual time of day when this would occur.

070-rotatelogs.sh
roll logfiles in /var/log for archival purposes. uses a config file to allow customization of how frequently each log should be rolled.

Shell Scripts - Part 05

2007-04-02T18:36:00.000+05:30

Shell Scripts - Part 05

041-hilow.sh
A simple number guessing game

042-nfmt.sh
A version of fmt, using nroff. Adds two useful flags: -w X for line width and -h to enable hyphenation for better fills.

043-newrm.sh
A replacement for the existing rm command that allows a rudimentary unremove capability through utilizing a newly created directory in the user's home directory. It can handle directories of content as well as individual files, and if the user specifies the -f flag, files are NOT archived, but removed.

044-unrm.sh
To search the deleted files archive for the specified file. If there is more than one match, show a list ordered by timestamp, and let the user specify which they want restored.

045-logrm.sh
To log all file deletion requests unless "-s" flag is used

046-formatdir.sh
To output a directory listing in a friendly and useful format.

047-locate.sh
To search the locate database for the specified pattern.

048-mklocatedb.sh
To build the locate database using find .

049-DIR.sh
To pretend we're the DIR command in DOS and display the contents of the specified file, accepting some of the standard DIR flags

050-findman.sh
Given a pattern and a man section, show all the matches for that pattern from within all relevant man pages.

Shell Scripts - Part 04

2007-04-02T18:07:00.000+05:30

Shell Scripts - Part 04

031-validint.sh
To validate integer input including negative integers.

032-validfloat.sh
To test whether a number is a valid floating point value. Note that this cannot accept scientific (1.304e5) notation.

033-valid-date.sh
To validate date including leap year rules.

034-echon.sh
To emulate the -n flag functionality with 'echo' for Unix systems that don't have it.

035-scriptbc.sh
A wrapper for 'bc' that returns the value of a formula.

036-filelock.sh
A flexible file locking mechanism.

037-colors.sh
Use these variables to easily have different color and format output. Make sure to output the reset sequence after colors (f = foreground, b = background), and use the 'off' feature for anything you turn on.

038-library-test.sh
Script to demonstrate use of the shell function library

039-library.sh
a collection of shell library utilities

040-guessword.sh
a simple word guessing game a la hangman

Shell Scripts - Part 03

2007-03-27T12:52:00.000+05:30

Shell Scripts - Part 03

021-suspenduser.sh

Suspend a user account for the indefinite future

022-deleteuser.sh

Delete a user account without a trace... Not for use with Mac OS X

023-validator.sh

Checks to ensure that all environment variables are valid. Looks at SHELL, HOME, PATH, EDITOR, MAIL, and PAGER

024-fixguest.sh

Clean up the guest account during the logout process

025-findsuid.sh

Find all SUID files or programs on the system other than those that live in /bin and /usr/bin, and output the matches in a friendly and useful format.

026-set-date.sh

Friendly front-end to the date command

027-inpath.sh

Verify that a specified program is either valid as-is, or can be found in the PATH directory list.

028-validalnum.sh

Ensures that input only consists of alphabetical and numeric characters.

029-normdate.sh

Normalizes month field in date specification to three letters, first letter capitalized. A helper function for hack #7, validdate. Exits w/ zero if no error.

030-nicenumber.sh

Given a number, show it with comma separated values expects DD and TD to be instantiated. instantiates nicenum or, if a second arg is specified, the output is echoed to stdout

Shell Scripts - Part 02

2007-03-27T12:39:00.000+05:30

Shell Scripts - Part 02

011-cgrep.sh

grep with context display and highlighted pattern matches

012-zcat.sh

This script should be either symbolically linked or hard linked to all three names - it allows users to work with compressed files transparently.

013-bestcompress.sh

Given a file, try compressing it with all the available compression tools and keep the compressed file that's smallest, reporting the result to the user. If '-a' isn't specified, it skips compressed files in the input stream.

014-fquota.sh

Disk quota analysis tool for Unix.

015-diskhogs.sh

Disk quota analysis tool for Unix, assumes all user accounts are >= UID 100. Emails message to each violating user and reports a summary to the screen

016-diskspace.sh

Summarize available disk space and present in a logical and readable fashion

017-newdf.sh

A friendlier version of df

018-mkslocate.sh

Build the central, public locate database as user nobody, and simultaneously step through each home directory to find those that contain a .slocatedb file. If found, an additional, private version of the locate database will be created for that user.

019-slocate.sh

Try to search the user's secure locate database for the specified pattern. If none exists, output a warning and create one. If secure locate db is empty, use system one instead.

020-adduser.sh

Add a new user to the system, including building their home directory, copying in default config data, etc. For a standard Unix/Linux system, not Mac OS X

Shell Scripts - Part 01

2007-03-27T12:22:00.000+05:30

Shell Scripts - Part 01

001-shpell.sh

An interactive spell checking program that lets you step through all known spelling errors in a document, indicate which ones you'd like to fix (and the correction), then applies them all to the file. The original version of the file is saved with a .shp suffix and the new version replaces the old.

002-spelldict.sh

Use the 'aspell' feature and some filtering to allow easy command-line spell checking of a given input (file)

003-convertatemp.sh

Temperature conversion script that lets the user enter a temperature in any of Fahrenheit, Celsius or Kelvin and receive the equivalent temperature in the other two units as the output.

004-loancalc.sh

Given a principal loan amount, interest rate, and duration of loan (years), calculate the per-payment amount.

005-addagenda.sh
Prompt the user to add a new event for the Agenda script

006-agenda.sh
Scan through the user's .agenda file to see if there are any matches for the current or next day

007-numberlines.sh
A simple alternative to cat -n, etc.

008-showfile.sh
Show the contents of a file, including additional useful info

009-toolong.sh
Only feed the fmt command those lines in the input stream that are longer than the specified length

010-quota.sh
A front-end to quota that works with fullword flags a la GNU

Editors available in Linux

2007-03-24T08:50:00.000+05:30

cooledit - a pretty powerful GUI text editor
emacs - powerful text editor that includes modules for reading and sending mail and postings to newsgroups, and a browser module. For editing T_EX and L^AT_EX files, the AucT_EX addon package is invaluable, and makes emacs pretty hard to beat as an editor with L^AT_EX.
jed - has pretty good emacs emulation (it can even read mail like emacs!). It does simple syntax highlighting for TeX files, including giving positioning of parentheses. It would seem to be pretty configurable and takes up much less disk space than emacs, although more than joe and muemacs. It works well in console mode, and still manages to use colors for menu bars and syntax highlighting. The program xjed which comes with some versions starts up its own X terminal when invoked.
joe - "Joe's Own Editor", a fairly powerful editor with a compact binary and an ability to emulate Wordstar, Emacs, Pico, and a few other editors.
jove - "Joe's Own Version of Emacs". I tried this out a couple of times and managed to crash it when making some minor errors in command syntax.
microemacs (JASSPA) - spinoff of muemacs. Pretty powerful and configurable, while not taking up too much disk space or memory.
muemacs - a fairly powerful emacs clone whose binary is actually smaller than that of the Joe editor.
nedit - an X Window based text editor. Of all text editors for Linux that I've seen, it has commands which are closest to Windows text editors, for cursor movement, highlighting, marking text, etc. It has very good syntax highlighting for both L^AT_EX and HTML.
pico - simple text editor. It often comes packaged with the Pine mail user agent.
vi - included with most Linux distributions. If you're not used to the syntax, it can be pretty hard to understand.
vim - improved version of vi
xedit - simple text editor included with many Linux distributions

Useful & Important Directories in Linux

2007-03-24T08:49:00.000+05:30

Different distributions have different directory structures, despite attempts at standardization such as the the Linux Filesystem Hierarchy Standard (FHS) organization.

/bin - essential UNIX commands such as ls, etc. Should contain all binaries needed to boot the system or run it in single-user mode
/boot - files used during booting and possibly the kernel itself are stored here
/dev - contains device files for various devices on system
/etc - files used by subsystems such as networking, NFS, and mail. Includes tables of disks to mount, processes to run on startup, etc.
/etc/profile.d - contains scripts that are run by /etc/profile upon login.
/etc/rc.d - contains a number of shell scripts that are run on bootup at different run levels. There is also typically an rc.inet1 script to set up networking (in Slackwar), an rc.modules script to load modular device drivers, and an rc.local script that can be edited to run commands desired by the administrator, along the lines of autoexec.bat in DOS.
/etc/rc.d/init.d - contains most of the initialization scripts themselves on an rpm-based system.
/etc/rc.d/rc*.d - where ``*'' is a number corresponding to the default run level. Contains files for services to be started and stopped at that run level. On rpm-based systems, these files are symbolic links to the initialization scripts themselves, which are in /etc/rc.d/init.d.
/etc/skel - directory containing several example or skeleton initialization shells. Often contains subdirectories and files used to populate a new user's home directory.
/etc/X11 - configuration files for the X Window system
/home - home directories of individual users
/lib - standard shared library files
/lib/modules - modular device driver files, most with .o extensions
/mnt - typical mount point for many user-mountable devices such as floppy drives, cd-rom readers, etc. Each device is mounted on a subdirectory of /mnt.
/proc - virtual file system that provides a number of system statistics
/root - home directory for root
/sbin - location of binaries used for system administration, configuration, and monitoring
/tmp - directory specifically designed for programs and users to store temporary files.
/usr - directory containing a number of subdirectory with programs, libraries, documentation, etc.
/usr/bin - contains most user commands. Should not contain binaries necessary for booting the system, which go in /bin. The /bin directory is generally located on the same disk partition as /, which is mounted in read-only mode during the boot process. Other filesystems are only mounted at a later stage during startup, so putting binaries essential for boot here is not a good idea.
/usr/bin/X11 - most often a symbolic link to /usr/X11R6/bin, which contains executable binaries related to the X Window system
/usr/doc - location of miscellaneous documentation, and the main location of program documentation files under Slackware
/usr/include - standard location of include files used in C programs such as stdio.h
/usr/info - primary location of the GNU info system files
/usr/lib - standard library files such as libc.a. Searched by the linker when programs are compiled.
/usr/lib/X11 - X Window system distribution
/usr/local/bin - yet another place to look for comon executables
/usr/man - location of manual page files
/usr/sbin - other commands used by superuser for system administration
/usr/share - contains subdirectories where many installed programs have configuration, setup and auxiliary files
/usr/share/doc - location of program documentation files under Mandrake and Red Hat
/usr/src - location of source programs used to build system. Source code for programs of all types are often unpacked in this directory.
/usr/src/linux - often a symbolic link to a subdirectory whose name corresponds to the exact version of the Linux kernel that is running. Contains the kernel sources.
/var - administrative files such as log files, used by various utilities
/var/log/packages - contains files, each of which has detailed information on an installed package in Slackware. The same file can also be found at /var/adm/packages, since the adm subdirectory is a symbolic link to log. Each package file contains a short description plus a list of all installed files.
/var/log/scripts - package installation scripts in Slackware are stored here. You can inspect these scripts to see what special features are included in individual packages.
/var/spool - temporary storage for files being printed, mail that has not yet been picked up, etc.

Useful files in Linux

2007-03-24T08:48:00.001+05:30

/boot/vmlinuz - the typical location and name of the Linux kernel. In the Slackware distribution, the kernel is located at /vmlinuz.
/dev/fd0 - first floppy disk drive
/dev/fd0H1440 - driver for the first floppy drive in high density mode. Generally, this is invoked when formatting a floppy drive for a particular density. Slackware comes with drivers that allow for formatting a 3.5" diskette with up to 1.7MB of space. Red Hat and Mandrake do not contain these device driver files by default.
/dev/fd1 - second floppy disk drive
/dev/hda - first IDE hard drive
/dev/hdc - on many machines, the IDE cdrom drive. Most often, there is a symbolic link called /dev/cdrom which is just a link to the true cdrom driver file.
/dev/null - used when you want to send output into oblivion
/etc/aliases - file containing aliases used by sendmail and other MTAs (mail transport agents). After updating this file, it is necessary to run the newaliases utility for the changes to be passed to sendmail.
/etc/bashrc - system-wide default functions and aliases for the bash shell
/etc/conf.modules - aliases and options for configurable modules
/etc/crontab - shell script to run different commands periodically (hourly, daily, weekly, monthly, etc.)
/etc/DIR_COLORS - used to store colors for different file types when using ls command. The dircolors command uses this file when there is not a .dir_colors file in the user's home directory. Used in conjunction with the eval command (see below).
/etc/exports - specifies hosts to which file systems can be exported using NFS. Man exports contains information on how to set up this file for remote users.
/etc/fstab - contains information on partitions and filesystems used by system to mount different partitions and devices on the directory tree
/etc/HOSTNAME - stores the name of the host computer
/etc/hosts - contains a list of host names and absolute IP addresses.
/etc/hosts.allow - hosts allowed (by the tcpd daemon) to access Internet services
/etc/hosts.deny - hosts forbidden (by the tcpd daemon) to access Internet services
/etc/group - similar to /etc/passwd but for groups
/etc/inetd.conf - configures the inetd daemon to tell it what TCP/IP services to provide (which daemons to load at boot time). A good start to securing a Linux box is to turn off these services unless they are necessary.
/etc/inittab - runs different programs and processes on startup. This is typically the program which is responsible for, among other things, setting the default runlevel, running the rc.sysinit script contained in /etc/rc.d, setting up virtual login terminals, bringing down the system in an orderly fashion in response to [Ctrl][Alt][Del], running the rc script in /etc/rc.d, and running xdm for a graphical login prompt (only if the default runlevel is set for a graphical login).
/etc/issue - pre-login message. This is often overwitten by the /etc/rc.d/rc.S script (in Slackware) or by the /etc/rc.d/rc.local script (in Mandrake and Red Hat, and perhaps other rpm-based distributions). The relevant lines should be commented out (or changed) in these scripts if a custom pre-login message is desired.
/etc/lilo.conf - configuration file for lilo boot loader
/etc/motd - message of the day file, printed immediately after login. This is often overwritten by /etc/rc.d/rc.S (Slackware) or /etc/rc.d/rc.local (Mandrake/Red Hat) on startup. See the remarks in connection with /etc/issue.
/etc/mtab - shows currently mounted devices and partitions and their status
/etc/passwd - contains passwords and other information concerning users who are registered to use the system. For obvious security reasons, this is readable only by root. It can be modified by root directly, but it is preferable to use a configuration utility such as passwd to make the changes. A corrupt /etc/passwd file can easily render a Linux box unusable.
/etc/printcap - shows the setup of printers
/etc/profile - sets system-wide defaults for bash shell. It is this file in Slackware that sets up the DIR_COLORS environment variable for the color ls command. Also sets up other system-wide environment variables.
/etc/resolv.conf - contains a list of domain name servers used by the local machine
/etc/securetty - contains a list of terminals on which root can login. For security reasons, this should not include dialup terminals.
/etc/termcap - ASCII database defining the capabilities and characteristics of different consoles, terminals, and printers
/etc/X11/XF86Config - X configuration file. The location in Slackware is /etc/XF86Config.
/proc/cpuinfo - cpu information
/proc/filesystems - prints filesystems currently in use
/proc/interrupts - prints interrupts currently in use
/proc/ioports - contains a list of the i/o addresses used by various devices connected to the computer
/proc/kcore - The command ls -l /proc/kcore will give the amount of RAM on the computer. It's also possible to use the free command to get the same information (and more).
/proc/version - prints Linux version and other info
/var/log/messages - used by syslog daemon to store kernel boot-time messages
/var/log/lastlog - used by system to store information about last boot
/var/log/wtmp - contains binary data indicating login times and duration for each user on system

Typical DOT files in LINUX ( Hidden Files )

2007-03-24T08:47:00.002+05:30

There is some redundancy across these programs. For example, the look and behavior of emacs can be customized by usinng the .emacs file, but also by adding the appropriate modifications to the .Xdefaults file. Default versions of these files are often installed in users' home directories when the software packages that use them are installed. If a program doesn't find its configuration file in the user's home directory, it will often fall back on a sytem-wide default configuration file installed in one of the subdirectories that the package lives in.

.bash_logout - file executed by bash shell on logout
.bash_profile - initialization of bash shell run only on login. Bash looks first for a .bash_profile file when started as a login shell or with the -login option. If it does not find .bash_profile, it looks for .bash_login. If it doesn't find that, it looks for .profile. System-wide functions and aliases go in /etc/bashrc and default environment variables go in /etc/profile.
.bashrc - initialization command run when bash shell starts up as a non-login shell
.cshrc - initialization commands that are run automatically (like autoexec.bat) when C shell is initiated
.emacs - configuration file for emacs editor
.fvwmrc - configuration file for fvwm window manager
.fvwm2rc - configuration file for fvwm2 window manager
.jedrc - configuration file for the jed text editor
.lessrc - typically contains key bindings for cursor movement with the less command
.login - initialization file when user logs in
.logout - commands run when user logs out
.wm_style - gives choice of default window manager if one is not specified in startx
.Xdefaults - sets up X resources for individual user. The behavior of many different application programs can be changed by modifying this file.
.xinitrc - initialization file when running startx. Can be used to activate applications, run a given window manager, and modify the appearance of the root window.
.xsession - configuration file for xdm

Shorthand at Command prompt

2007-03-24T08:47:00.001+05:30

/ - root directory
./ - current directory
./command_name - run a command in the current directory when the current directory is not on the path
../ - parent directory
~ - home directory
$ - typical prompt when logged in as ordinary user
# - typical prompt when logged in as root or superuser
! - repeat specified command
!! - repeat previous command
^^ - repeat previous command with substitution
& - run a program in background mode
[Tab][Tab] - prints a list of all available commands. This is just an example of autocomplete with no restriction on the first letter.
x[Tab][Tab] - prints a list of all available completions for a command, where the beginning is ``x''
[Alt][Ctrl][F1] - switch to the first virtual text console
[Alt][Ctrl][Fn] - switch to the n^th virtual text console. Typically, there are six on a Linux PC system.
[Alt][Ctrl][F7] - switch to the first GUI console, if there is one running. If the graphical console freezes, one can switch to a nongraphical console, kill the process that is giving problems, and switch back to the graphical console using this shortcut.
[ArrowUp] - scroll through the command history (in bash)
[Shift][PageUp] - scroll terminal output up. This also works at the login prompt, so you can scroll through your boot messages.
[Shift][PageDown] - scroll terminal output down
[Ctrl][Alt][+] - switch to next X server resolution (if the server is set up for more than one resolution)
[Ctrl][Alt][-] - change to previous X server resolution
[Ctrl][Alt][BkSpc] - kill the current X server. Used when normal exit is not possible.
[Ctrl][Alt][Del] - shut down the system and reboot
[Ctrl]c - kill the current process
[Ctrl]d - logout from the current terminal
[Ctrl]s - stop transfer to current terminal
[Ctrl]q - resume transfer to current terminal. This should be tried if the terminal stops responding.
[Ctrl]z - send current process to the background
reset - restore a terminal to its default settings
[Leftmousebutton] - Hold down left mouse button and drag to highlight text. Releasing the button copies the region to the text buffer under X and (if gpm is installed) in console mode.
[Middlemousebutton] - Copies text from the text buffer and inserts it at the cursor location. With a two-button mouse, click on both buttons simultaneously. It is necessary for three-button emulation to be enabled, either under gpm or in XF86Config.

Basic Linux Commands

2007-03-24T08:46:00.001+05:30

In the following command list, the distinction between upper case and lower case letters is important. Most of the commands are utilities that are run by invoking their own executable files. In some cases, they are commands which are internal to a shell such as bash (shell builtins). The shell builtins are indicated. There are now many utilities that are included with either the Gnome or the KDE desktop environments, so many that it would be difficult to include them all here. In many cases, they duplicate the functionality of one or more of the programs listed below. I would suggest consulting the online documentation for these packages.

On rpm-based systems, to find out which package owns the command foo (where foo is a standalone executable), use the command rpm -q -f foo.

a2p - translation utility from awk to Perl
a2ps - translation utility from ``any'' to Postscript
ac - print statistics concerning user connect time
access - determine whether a file can be accessed
acroread - Adobe utility for viewing pdf files
adduser - used by root to add user to system
- usage: adduser userid
afio - utility to copy or restore files to an archive file. This utility is not part of the basic internal and external programs under Red Hat Linux. It is available as an rpm on the rpmfind.net site.
agetty - enables login on terminals. See getty, mgetty, and uugetty.
ali - list mail aliases
alias - assign name to specified command list. This is actually a shell builtin. On my Red Hat system, I have global alias commands in my /etc/bashrc file and in my /.bashrc file. On my Slackware box, I have made the rm command a little bit safer with
- alias rm='rm -i'
so that you can't recursively delete your /dev directory without telling the system you're sure you want to do it.
alien - utility to convert to and from different Linux package formats. Can handle Debian (deb), Stampede (stp), Red Hat (rpm) and Slackware (tgz) packages.
apropos - display command names based on keyword search
- usage: apropos keyword
apsfilter - printer filter called by lpd to deal with printing different types of files. This is a fairly sophisticated print filter. It is not set up by default in Slackware. It used to be available on the second cd of a Slackware distribution. Since 4.0, it is available as one of the main packages in the ap set. Read the mail that the installation program sends to the root user. I believe that Red Hat uses its own printer filters.
ar - create, modify and extract from archives
arch - print machine architecture type
as - the portable GNU assembler
asapm - AfterStep laptop advanced power management utility
ash - a shell, a very simple shell program sometimes used on boot diskettes since it takes up much less space than bash, tcsh, zsh, etc.
asload - AfterStep cpu load monitor
asmail - AfterStep mail checking utility
asmodem - AfterStep utility to monitor modem status
aspell - a spell checking program along the lines of ispell
aspostit - X Window postit note utility
at - executes a shell script at specified time. Use atq to show pending jobs, and atrm to remove jobs from the queue.
- usage: at time
- or: at -f file time
atq - shows pending jobs queued by at. If run by root, shows everybody's pending jobs.
atrm - removes pending jobs queued by at. Use atq to determine the identities of various jobs.
- usage: atrm job
awk - searches for and process patterns in a file
banner - print banner to standard output. Syntax is
- banner [option] [characters]
bash - Bourne again shell. This is the default shell in the Red Hat installation.
batch - queue, examine, or delete jobs for later execution. See at.
bc - a language (compiler) similar to C, with unlimited precision arithmetic
bg PID - send process with pid ``PID'' to the background. This is the same as executing [Ctrl]z while interacting with the running process. This is a shell builtin.
bh - puts a job in the background. This is a shell builtin.
biff - mail notification utility. Notifies user of mail arrival and sender's name.
bind - displays or redefines key bindings. This is a shell builtin.
bison - parser generator similar to yacc
bru - a powerful backup utility program. Commercial. Demonstration versions are often included with Linux distributions such as Red Hat.
bsh - equivalent to ash
bunzip2 - used to uncompress files compressed with bzip2
byacc - parser generator
bzip2 - compresses with algorithm different from gzip
bzless - view bzipped files
c++ - invokes GNU C and C++ compiler
cal - displays a 12-month calendar for the given year or a one-month calendar of the given month
- usage: cal month year
cat - combine, copy standard input to standard output. Used to join or display files.
cd - change working directory. This is a shell builtin in bash, tcsh and zsh.
cdplay - command line utility for playing audio cds
cfdisk - similar to fdisk, but menu-driven
chat - used to interact with a modem via a chat script
chgrp - changes group associated with file. Can be used to change the group associated with subdirectories and files of a directory.
- usage: chgrp group files
- or: chgrp -R group files
chkconfig - Query or update system services/daemons for different runlevels. Manipulates the various symbolic links in /etc/rc.d. This utility is included with many rpm-based distributions such as RedHat and Mandrake. It is designed to work with System V initialization scripts. Graphical tools for configuring system services include ntsysv, tksysv and ksysv (the latter is a KDE utility).
chmod - set permissions (modes) of files or directories. A value of 4 is used for read permission. A value of 2 is used for write permission. A value of 1 is used for execute permission. See umask for default file permissions upon file creation. Chmod can also be used to change the suid bit on files. The syntax for the symbolic version is
- chmod [options] who operation permission file-list
The syntax for the absolute version is
- chmod [options] mode file-list
To set the uid to the owner's permissions, use
- chmod u +s file-name
To set the uid to the group's permissions, use
- chmod g +s file-name
There are lots of security issues related to allowing a program to have root's permissions when run by an ordinary user. I don't pretend to understand all of these issues.
chown - changes ownership of a file. Can be used recursively.
- usage: chown userid files
- or: chown -R userid files
chsh - change default shell
ci - creates or records changes in an RCS file
clear - clear screen command
cmp - compares two files for differences
- usage: cmp file1 file2
co - retrieves an unencoded version of an RCS file
comm - compares sorted files
configure - automatically configures software source code
color-xterm - color xterm program. Under Red Hat, this is just a link to xterm-color.
control-panel - graphical system configuration tool under Red Hat.
cp - copies on or more files. Recursive copying is one simple way of archiving part of a directory structure. Use the command as follows:
- cp -r /sourcedirectory /targetdirectory
cpio - direct copy of files to an output device. Allows creation of archive file spanning multiple diskettes. Allows one directory structure to be mirrored elsewhere on the partition or on another partition. In order to back up an entire directory structure on diskettes, cd to the directory and use the following command:
- find . -depth -print | cpio -ov > /dev/fd0
To restore from diskettes, use:
- cpio -iv < /dev/fd0
The cpio command will prompt the user to insert more diskettes as they are needed. The command for mirroring a directory structure is the following:
- find . -depth -print | cpio -pv /destinationdirectory
This copies the working directory and its contents, including subdirectories, into /destinationdirectory. In order to copy an individual file which is larger than a floppy, use:
- find . -name nameoffile -print | cpio -iv > /dev/fd0
cpkgtool - Slackware tool to install, uninstall and query packages. Front end to installpkg, removepkg, makepkg. This is the graphical version that uses ncurses.
cpp - GNU C-compatible compiler preprocessor
crontab - schedules command to run at regularly specified time
csh - run C shell
csplit - separate files into sections. See also split.
cvs - manages concurrent acces to files in a hierarchy. Stands for concurrent version system. Is built on RCS. It stores successive revisions of files efficiently and ensures that access to files by multiple developers is done in a controlled manner. Useful when many developers are working on the same project.
cut - selects characters or TAB-separated fields from lines of input and writes them to standard output
date - displays or sets date and time
- usage: date
- or: date date
dd - direct copy of file from one device to another. Can be used to make copies of boot or root diskettes for installing Linux. It can be used, for example, to make and exact copy of a floppy disk, as follows. First, place the diskette to be copied in the floppy drive. Then,
- dd if=/dev/fd0 ibs=512 > floppy.copy
- Replace the diskette with a fresh diskette.
- dd if=floppy.copy bs=512 of=/dev/fd0
The ibs and bs options specify the block sizes for input and for both input and output. A boot disk image can be directly copied to a floppy using the second of the two dd commands above.
declare - declares attributes for a variable (same as typeset). This is a shell builtin.
df - displays capacity and free capacity on different physical devices such as hard drive partitions and floppy drives that are mounted on the file system. Gives free space in blocks. With the (undocumented) option -h, the program gives free space in Mb or Gb. This is useful for those accustomed to thinking of the capacity of a high-density 3.5 inch diskette as 1440k.
diff - displays differences between two files
- usage: diff file1 file2
diff3 - compares three files and reports on differences
dip - used to set up a SLIP or PPP connection. It can be used to set up an outgoing SLIP connection or an incoming connection.
diplogin - used for setting up incoming dip connections. See the man page for dip.
dir - a variation of the GNU ls command that defaults to printing file names in columns
dircolors - set colors for GNU ls command. In Slackware, this command is run by the /etc/profile script. Then, whenever xterm is run with the -ls (login shell) option, ls displays different colors for different types of files. Typical usage is eval `dircolors -b`. In Red Hat and Mandrake, I get color directories by aliasing the ls command (see below).
display - set display for output of programms under X Windows. Can be used to run a program on a remote machine while displaying the output on a local machine. The remote machine must have permission to send output to the local machine. This is actually an environment variable. See the more detailed discussion in connection with the xhost command below.
dmesg - displays messages from /var/log relative to the most recent boot
dos - invoke the DOSEMU DOS emulator
du - displays information on disk usage. The command
- du / -bh | less
will display detailed disk usage for each subdirectory starting at root, giving files sizes in bytes.
dumpkeys - print information about the keyboard driver's translation tables to standard output
dvilj - send a dvi file to a Laserjet printer. There are specialized versions for individual models of Laserjet printer.
dvilj2p - specialized version of dvilj for the IIp series of printers. See above.
dvips - send a dvi file to a Postscript printer, to a Postscript capable Laserjet printer, or to a file (with the -o option). There is a switch to print only a subset of the pages, and another switch to print in landscape mode. Use -t landscape, which is one of the arguments to the paper type switch. If you have one page of a document that is a wide table, and you wish to print this in landscape mode, use
- dvips filename -pp pagenumber -t landscape
e2fsck - check an ext2 filesystem. The syntax is
- e2fsck /dev/devicename
where the filesystem is on /dev/devicename. The device should not be mounted, and this program must be run as root.
echo - write arguments to standard output. One use is to print out information about environment variables, as in
- echo $PATH - list paths to search
- echo $HOME or echo ~ - list name of home directory
This is a shell builtin.
editres - a dynamic resource editor for X Toolkit applications. Allows the user to change X resources for individual applications.
efax - fax program
efix - convert between fax, text, bit-map and gray-scale formats
egrep - search files for lines that match regular expressions. Runs faster than grep and fgrep.
elm - an interactive mail system
elvis - a version of the vi text editor
emacs - screen oriented text editor
env - desplay the current environment or set a variable equal to a new value
eval - scans and evaluates the command line. See dircolors command. This is a shell builtin.
ex - interactive command-based editor. The man page lists it as being the same as vim, an improved version of vi.
exec - system call which creates a subshell to execute a binary or a script. This is a shell builtin.
execve - a variation of the exec command.
exit - exit a shell. This is a shell builtin.
expand - convert tabs in files to spaces and write to standard output
expect - a program that ``talks'' to other interactive programs according to a script. Following the script, Expect knows what can be expected from a program and what the correct response should be. An interpreted language provides branching and high-level control structures to direct the dialogue. In addition, the user can take control and interact directly when desired, afterward returning control to the script.
export - place the value of a variable in the calling environment (makes it global). This is a shell builtin.
expr - utility evaluates an expression and displays the result
f2c - FORTRAN to C translator
f77 - FORTRAN 77 compiler
false - null command that returns an unsuccessful exit status
fax - simple user interface to efax and efix programs
fc - views, edits, and executes commands for the history list. This is a shell builtin.
fdformat - low level format of a floppy device
fetchmail - retrieve mail from a remote mail server and pass it to local SMTP agents on the local machine
fdisk - used to partition hard drives
- usage: fdisk device
fg PID - bring a background or stopped process with pid ``PID'' to the foreground. This is a shell builtin. If only one process is running in background mode, fg with no argument is sufficient to bring it to the foreground
fgrep - search for patterns in files
file - displays classification of a file or files according to the type of data they contain
find - find files according to a large variety of search criteria. The find command that I use the most is
- find . -name filename -print
in order to find files matching a particular name on the working directory and all subdirectories. Find can be incredibly powerful, but it is incredibly obscure.
finger - display information about a specified userid or userids
fmt - simple text formatting utility. Tries to make all nonblank lines nearly the same length.
fold - break lines of specified files so they are no wider than a specified lengths
fortune - available in the bsdgames package in Slackware and other distributions. Put a call to fortune in /etc/profile and get something inspirational or amusing every time you fire up an xterm as a login shell.
free - gives used and free memory on system along with other useful information
fromdos - takes a DOS text file from stdin and sends a UNIX file to stdout.
fsck - file system check and repair
ftp - file transfer over network
g++ - C++ compiler
g77 - GNU Fortran 77 compiler
gawk - GNU awk, mostly for processing delimited text files
gcc - invoke C, C++ compiler
getipts - parses arguments to a shell script. This is a shell builtin.
getkeycodes - print kernel's scancode-to-keycode mapping table
ghostscript - set of printing utilities. It seems to be obligatory to have this if a T_EX installation such as teT_EX is installed. How they communicate with one another is somewhat obscure.
ghostview - Aladdin ghostscript interpreter/previewer
gimp - image manipulation and paint program
glint - Red Hat graphical front end for the rpm package installer and manager.
grep - used to find a string within a file. The -i option returns matches without regard to case. The -n option means that each line of output is preceded by file name and line number. The -v option causes non-matched lines to be printed.
- usage: grep pattern files
- or: grep -i pattern files
- or: grep -n pattern files
- or: grep -v pattern files
groupadd - create a new group on the system
groups - shows which groups you are in
grub - Gnu grand unified bootloader. Can be used instead of lilo to boot multiple operating systems. I encountered a couple of snafus trying to install grub on my home machine after installing Mandrake 8.0 and choosing the lilo bootloader during the initial install. The Mandrake installation program set up /boot/vmlinuz as a symlink to the actual kernel, vmlinuz-2.4.3-20mdk. It took me a while to figure out that grub doesn't understand symbolic links. The documentation suggests installing grub on a diskette using the ``dd'' command. This refused to work, but
- grub-install '(fd0)'
did work. The single quotes are necessary. The files necessary to run grub are normally located in /boot/grub. Once the file menu.lst has been edited and appropriated entries added to boot the different operating systems on one's hard disk(s), the following sequence of commands can be used to install grub in the master boot record (MBR) sector of the hard disk:
- root (hd0,x)
- setup (hd0)
Here, the x should be replaced by the partition where the /boot/grub directory is located, which is probably the root partition of the Linux system. Note that grub has its own conventions for naming devices and numbering partitions, so that for example a partition which is called hda6 under Linux will be called (hd0,5) by grub.
grub-install - command to install grub on the hard drive (or floppy drive).
gunzip - used to uncompress files compressed with gzip
gv - PostScript and PDF previewer, based on ghostview
gvim - see vi
gzexe - compresses executables
gzip - used to compress or decompress files
halt - shut down system as root, without reboot, immediately
hash - remembers the location of commands in the search path. This is a shell builtin.
head - displays first part of a file
history - command for viewing and manipulating the shell command history list
host - look up host names using domain server
hostname - used to get or set hostname. Typically, the host name is stored in the file /etc/HOSTNAME.
hwclock - used to query and set the hardware clock
hylafax - commercial fax program
id - display userid and groupid
inetd - daemon which starts up other daemons on demand. Configured in /etc/inetd.conf.
ifconfig - display (as root) information on network interfaces that are currently active. First ethernet interface should be listed as eth0, second as eth1, etc. First modem ppp connection should be listed as ppp0, etc. The ``lo'' connection is ``loopback'' only.
ifdown - shut down the network interface
ifup [interface_name] - start up the interface
info - display system information. This is the GNU hypertext reader.
init - the mother of all processes, run at bootup, executes commands in /etc/inittab. Can be used (with root privileges) to change the system run level.
- usage: init run_level
insmod - used (by root) to install modular device drivers
installpkg - Slackware command to install one of the packages from the program sets
intr - interrupt key, usually [Ctrl-C]
ispell - checks files for spelling errors
- usage: ispell files
jed - programmer's file editor. Behaves like emacs. Has modes for T_EX, FORTRAN, C, etc.
jobs - displays list of current jobs in the background. This is a shell builtin.
joe - simple WordStar-like text editor. It can be invoked in emacs emulation mode with jemacs and in WordStar emulation mode with jstar.
jove - Joseph's Own Version of Emacs. A simple emacs clone.
kbd_mode - print current keyboard mode
kernelcfg - GUI to add/remove kernel modules (as root in X terminal).
kerneld - kernel daemon, a process that stays in memory and does all sorts of useful stuff, like automatic loading of device driver modules
kikbd - a utility program that comes with KDE that allows users to switch on the fly among different international keyboards. It can be used under different window managers than kfm.
kill - sends a signal to (especially to terminate) a job or process. This is a shell builtin in bash, tcsh and zsh.
killall - kill processes by name. Kill all processes which are instances of the speciffied program. Also used to send signals to processes or restart them.
killall5 - kill all processes except the ones on which it depends
last - generate a listing of user logins
lastlog - prints the last login times of all users
latex - compile a L^AT_EX file
ldconfig - creates the necessary links and cache (for use by the run-time linker, ld.so) to the most recent shared libraries found in the directories specified on the command line, in the file /etc/ld.so.conf, and in the trusted directories (/usr/lib and /lib). Ldconfig checks the header and file names of the libraries it encounters when determining which versions should have their links updated. Ldconfig ignores symbolic links when scanning for libraries.
ldd - list the shared libraries on which a given executable depends, and where they are located
leave - display reminder at specified time
less - Linux alternative to ``more'' command. Displays text files, one screenful at a time. When less pauses, there is a large number of available commands to tell it what to do next. One can scroll both forwards and backwards.
let - evaluates a numeric expression. This is a shell builtin.
lilo - installs boot loader on the boot sector of a hard drive, of a diskette, or in another location. My 486 has a hard drive that is too large for the machine's BIOS, so I have to boot from a floppy. To create a boot diskette, I do the following (as root):
- /sbin/fdformat /dev/fd0H1440
- /sbin/mkfs.ext2 /dev/fd0
- mount -t ext2 /dev/fd0 /mnt/floppy
- cp -dp /boot/* /mnt/floppy
- /sbin/lilo -C /etc/lilo.flop
The -C option to lilo has lilo use the lilo.flop file instead of the default lilo.conf.
linuxconf - interactive tool for configuring Linux system. Uses X if loaded. This is a Gnome tool. It comes with my Red Hat distribution, and is not included with Slackware. It would seem to be the easiest way to configure Linux under Slackware. Version 1.15 is available for Slackware. There is a pretty good introduction to the use of linuxconf in the Red Hat 5.2 installation manual, which is available online at their web site.
ln - creates a link to a file. Used to create hard links and, with the -s option, symbolic links which can link files on different disk partitions. The syntax is
- ln [options] source [dest]
locate filename - find the file name which contains the string ``filename''. The syntax is easier than the find command.
lock - temporarily lock terminal
lockfile - create semaphore file(s), used to limit access to a file
- log in to system
logname - consult /etc/utmp for user's login name
logout - execute logout as individual user and bring up login: prompt
look - look for strings in files
lpq - show print jobs that are waiting
lpr - send file to be printed
lprm - cancel a job from print queue
ls - list directory contents. To get colored directory listings under Red Hat, Mandrake, etc., use
- ls -color
To get this all the time, add
- alias ls='ls -color=auto'
to .bashrc. The following command
- alias ls='ls -Fskb -color=auto'
will give directory listings in color, with file sizes in kilobytes, and append a character to the file to indicate its type.
lsattr - list attributes of files in ext2 file system
lsmod - used (by root) to show kernel modules currently loaded
lspci - utility to display information on pci buses and hardware devices attached to them. Part of the pciutils package that comes with many Linux distributions.
lspnp - utility to display information about pnp devices. Part of the pcmcia or kernel-pcmcia package, depending on the distribution.
m4 - an implementation of the traditional UNIX macro processor. It can be used with the sendmail configuration package in Red Hat (and Slackware) to generate a sendmail.conf configuration file without having to edit the configuration file directly.
magicfilter - general purpose printer filter. See apsfilter above. apsfilter is the printer filter that comes with the Red Hat and Slackware distributions.
mail - sends or reads electronic mail
make - keeps a set of programs current. This is a utility that helps when developing a set of programs. It works by executing a script called makefile, Makefile or GNUmakefile in the working directory. It is very often used in combination with configure when compiling and installing noncompiled software packages.
makebootdisk - command in Slackware to do just what the name says
MAKEDEV - executable script to make device files on /dev
makeswap - configures swap space
man - displays information from online Unix reference manual
manpath - attempt to determine path to manual pages
mc - Midnight Commander file manager and visual shell
mesg - enables/disables reception of messages
minicom - terminal program
mkdir - create a directory
mkfs - create a file system (format) on a device or partition. Should be invoked after lowlevel formatting of the disk using fdformat. It has several versions which are all links to the basic program, such as mkfs.ext2 and mkfs.msdos.
mkswap - creates a Linux swap space on the specified hard disk parition (root privileges neede)
- usage: mkswap device
more - list file contents, stopping after each full screen
mount -t [fstype] [device] [mountpoint] - mount device using filesystem of type [fstype] with device name [device] at the location [mountpoint] in the filesystem directory tree
mount -a - mount all filesystems according to the specifications in /etc/fstab
mouseconfig - mouse configuration utility under Red Hat. Located in /usr/sbin.
mpage - print multiple pages per sheet on a Postscript printer. Can also be used to print a page in landscape mode.
Mtools - package of MS-DOS utilities. Includes the following commands.
- mcd - changes working directory on DOS disk
- mcopy - copies DOS files from one directory to another
- mdel - deletes DOS files
- mdir - lists contents of DOS directories
- mformat - adds DOS formatting information to a disk
- mtype - displays contents of a DOS file
The default device for execution of these commands is /dev/fd0 and can be referred to as ``a:''.
mv - moves (renames) files
netconf - used (as root) to set up network
newaliases - rebuilds the /etc/aliases database used by sendmail. Must be rerun every time /etc/aliases is modified for the changes to take effect.
newgrp - similar to login. Changes user's identification
nice program_name - sets the priority of the program ``program_name''.
nm - lists the symbols from object files objfile. If no object files are given as arguments, nm assumes `a.out'.
nohup - runs a command that keeps running after logout. The command is in principle immune to hangups, and must have output to a non tty. According to Linux in a Nutshell, this is necessary only in the Bourne shell, since modern shells preserve background processes by default.
ntsysv - run level editor under Red Hat. This is the equivalent of tksysv, but does not require a graphical interface.
nxterm - color xterm program. The man page for nxterm under Red Hat brings up the same page as xterm.
od - dumps contents of a file
passwd - change login password
paste - joins corresponding lines from files
patch - updates source code. Attempts to update a file from a file of change information, or pathces, created by diff.
pathchk - determine validity and portability of filenames
pdflatex - part of the pdftex program suite. Produces pdf output from a L^AT_EX file.
pdftex - produces pdf output from a TeX file. See also pdflatex. This program is part of the tetex 0.9 distribution that is included with Red Hat 5.2 and above, and with Slackware 4.0 and above. It is also available as a separate program.
perl - practical extraction and report language
pg - display data one screenful at a time
pico - simple screen oriented text editor. It is included as part of the Pine program.
ping - check if Internet computer is responding. Can also measure the time it takes the queried computer to respond.
pkgtool - Slackware tool to install, uninstall and query packages. Front end to installpkg, removepkg, makepkg. The cpkgtool is the ncurses graphical version of this program.
popclient - retrieve mail via the Post Office Protocol. Supports POP2 and POP3.
popd - pops the top directory of the directory stack and uses cd to change to that directory. This is a shell builtin.
pr - paginates files for printing
printenv - display list of environment variables
printtool - run (as root) in an X terminal to configure your printer(s)
ps - displays status of processes. Use the -a option for processes for all users. Use the -x option to include processes not attached to a terminal.
pstree - display processes in the form of a tree structure. Killing a parent process will also kill all the children and their descendants.
pushd - pushes the argument onto the top of the directory stack and uses cd to change to that directory. This is a shell builtin.
pwd - print absolute path of working directory. This is a shell builtin.
pwchk - checks the integrity of password and shadow files
pwconv - converts passwords to the shadow password format
pwunconv - unconverts passwords from the shadow password format. Generates a standard Unix password file.
python - interpreted, interactive, object-oriented programming language
rcp - copy one or more files to or from remote computer. The syntax is poorly explained in the documentation that I have, including the man pages. Usage is:
- rcp filename username@remotehost:path
The user's home directory on the remote system must contain the file .rhosts with a list of users (preceded by the full domain name or exact IP address of their machine) with access privileges.
- localhostname username
rcs - creates or changes the attributes of an RCS file. Stands for Revision Control System.
rdev - query/set image root device, swap device, RAM disk size, or video mode in kernel
read - reads line from standard input. This is a shell builtin.
readonly - declares a variable to be read only. This is a shell builtin.
reboot - in Slackware, reboots the system. Seems to be equivalent to shutdown -r now in generic Linux.
renice program_name - resets the priority of process ``program_name''.
reset - used to reset the screen characteristics. This is useful if the screen gets messed up from, for example, trying to display a binary file in an xterm.
return - exits from a function. This is a shell builtin.
rlog - prints a summary of the history of an RCS file
rlogin - log in to remote computer. The general syntax is as follows, using the UQAM Nobel machine as an example:
- rlogin -l userid nobel.si.uqam.ca
The remote computer must recognize the local user and the local machine. See the rcp command for how to set up the .rhosts file on the remote machine.
rm - remove files or directories. With the -r (recursive) option (very dangerous!), can be used to remove the contents of a specified directory including all subdirectories.
rmail - interpret and handle remote mail received via uucp
rmdir - remove empty directories
rmmod - used to remove modular device drivers
route -n - show routing table. The n option returns numerical addresses rather than names.
rpm - invokes the Red Hat package manager in command line mode. I often use this command in query mode to query packages about what files they contain and to find out which package owns a particular file. Examples are
- rpm -qil foo. Gives package information and a file list for the package foo.
- rpm -qfil foo. Gives package information and a file list for the package that owns the file foo. Foo must be in the working directory, or the full path to foo must be specified.
We need to find out about installing the rpm package on a Slackware box. It's probably better to use a package converter such as alien.
rpm2tgz - an extremely useful utility on Slackware systems that converts rpm packages to tgz format. They can then be installed using the installpkg command (or pkgtool).
rsh - execute shell command on a remote computer. See rcp and rlogin.
rstat - summarize host's status: uptime, load averages, and current time
ruptime - show host status of local machines
rusers - list who is logged on local machines
rwall - write to all users over a network
rwho - show who is logged in on a LAN. The rwho service must be enabled for this command to run. If it isn't, run ``setup'' as root. I don't understand this last remark, which comes from ``Linux Newbie Administrator Guide''.
rxvt - a terminal program similar to xterm, but which has less features and uses less memory
sed - edits a file (not interactively). Also a tool for processing text files.
set - set or display value of shell variables. This is a shell builtin. The command
- set | less
prints the current user environment, giving the values of currently defined variables.
setenv - set or display value of environment variables
setserial - used by root to configure a serial port
setterm - set terminal attributes for a virtual console
setuid - set the id of a program when it is run. Used, for example, to give root privileges to a program run by an ordinary user. This is actually done by running the chmod program as root. See the chmod command for the syntax.
setup - Slackware program to set up program sets and configure system. Setup devices and file systems, mount root file system
sh - standard UNIX shell. On Linux, just another name for bash.
shift - promotes each command-line argument. This is a shell builtin.
showmount - show information about an nfs server
shutdown - reboot or shut down system as root, after specified amount of time. With the -r option, reboot. With the -h option, halt the system.
- usage: shutdown -r minutes
sleep - creates process that sleeps for specified interval
sliplogin - attaches a SLIP interface to standard input. Used to allow dialin SLIP connections.
sort - sorts and/or merge files
split - split file into specified number of segments
ssh - secure shell. Apparently has many of the same functionalities as rlogin, telnet, ftp, rsh, etc., with better security and encryption features. We may want to learn how to set this up and use it.
startx - front end to xinit in Linux. This is a script which starts up X clients and shuts down the X server on exit from the window manager.
startx -- :1 - start the next X window session on the display 1 (the default is opened on display 0). One can switch between different graphical displays using [Ctrl][Alt][F7], [Ctrl][Alt][F8], etc.
stty - sets or displays operating options for terminal
su - log in as another user, including root
sudo - allows individual users to have root permission to perform specified tasks
swapoff - disables swap disk
swapon - enables swap disk
symlinks - provide list of and information about symbolic links
sync - writes memory buffers to physical devices
systat - query host for system information
tac - print file in reverse
tail - displays the last part of a file
talk - visual communication program that copies lines from one terminal to that of another user
tar - file compression and archiving utility. I find the syntax of this command to be frustratingly opaque. The following works for me. To use this command to unzip gzipped tarballs in verbose mode, use
- tar -xvzf filename.tgz
To create a tarball from files in a given directory and its subdirectories, use
- tar -cvzf filename.tgz sourcename
Sourcename can be the name of a single file, a wildcard such as *, or the name of a subdirectory. There seem to be two different conventions concerning gzipped tarballs. One often encounters .tar.gz. The other popular choice is .tgz. Slackware packages use the latter convention. The command can also be used to archive a file, a group of files, or a directory (with its subdirectories) on tape or onto floppies. If the material to be archived exceeds the capacity of the backup medium, the program will prompt the user to insert a new tape or diskette. Use the following command to back up to floppies:
- tar -cvf /dev/fd0 filename(s) or directoryname(s)
The backup can be restored with
- tar -xvf /dev/fd0
Tar can be used for other things. To mirror all the files and subdirectories in from-stuff to to-stuff, use the commands
- cd from-stuff
- tar cf - . | (cd ../to-stuff; tar xvf -)
No tar file is ever written to disk. The data is sent by pipe from one tar process to another. This example is taken from Running Linux, p.177. To list the table of contents of a tar archive, use
- tar tvf tarfile
To extract individual files from a tar archive, use
- tar xvf tarfile files
where files is the list of files to extract. When extracting files, tar creates missing subdirectories underneath the current directory in which the cammand is invoked.
tcl - scripting language
tcsh - extended version of the C shell
tee - copy standard input to standard output and one or more files
telinit - used to change run level. Exact run level that corresponds to single-user, multi-user, and X levels depends on distribution.
telnet - remote login over network
test - evaluates an expression or compares arguments. This is a shell builtin in bash, tcsh and zsh.
tftp - user interface to TFTP protocol
time - displays times for the current shell and its children. This is a shell builtin. Strange, because there is also a /usr/bin/time program on my Red Hat system.
tin - Netnews reader
tkdesk - graphical desktop file manager for X
tksysv - graphical runlevel editor under Red Hat. Allows root to configure the services that are started at each run level.
tload - display system load average in graph format
top - dynamically displays process status
touch - update access and modification times of a file. If the file does not exist on disk, an empty file is created.
tr - translation utility that can be used, for example, to replace specified characters in a text file
trap - traps a signal. This is a shell builtin.
true - null command that returns a successful exit status
tset - initializes terminal
tty - shows special file that represents your terminal. Displays the terminal pathname.
type - displays how each argument would be interpreted as a command. This is a shell builtin.
typeset - declares attributes for a variaable (same as declare). This is a shell builtin.
ul - translate underscores to underlining
umask - establishes the file-creation permissions mask. Usage is
- umask xyz
The system subtracts x, y and z from the owner, group and other file permissions that it would otherwise assign to new files. This is a shell builtin.
umount [device] - finish writing to the device and remove it from the active filesystem. The command umount -a will (re)mount all file systems listed in /etc/fstab.
unalias - remove name previously defined by alias. This is a shell builtin.
uname - displays information about the system. With no arguments, it displays the name of the operating system. With the -a option, it displays information about the operating system, the host name, and hardware.
uniq - displays lines of a file that are unique
unset - removes a variable or function. This is a shell builtin.
unzip - uncompress files compressed with the zip utility, compatible with DOS PKzip
updatedb - update file database used by locate command
uptime - shows the time, how long the system has been up, the number of users, and average load.
useradd - same as adduser
userdel - remove an account (as root). The user's home directory and undelivered mail must be dealt with separately.
users - prints list of users on the system
vdir - variant of the GNU version of the ls command. Defaults to printing out the long version of directory entries.
vi - standard screen oriented Unix editor
view - vi in read-only mode
vim - improved vi editor
vrfy - query remote host to verify the accuracy of an email address
w - display info about userids and active processes
wait - waits for a background process to terminate. This is a shell builtin.
wc - displays number of lines, characters and words in a file
Wharf - the AfterStep application dock module
whatis - display one-line summary of specified command
whereis - use to find utilities in standard locations
which - used to find utilities in search path. Will return the absolute directory path of the named utility program.
who - display information about currently logged in userids
whoami - display information about userid that is currently logged in
wish - front end to tk, an X window extension of tcl
workbone - console based cd player
workman - graphical cd player program
write - send messages to another local user
X - starts up the X server. Can be invoked with
- X -quiet -query remotemachineaddress
in order to get a graphical login screen on the remote machine. See the discussion in connection with xdm below.
xadm - display advanced power management BIOS information
xargs - converts standard output of one command into arguments for another. This is one of those powerful but obscure commands. Xargs reads arguments from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is /bin/echo) one or more times with any initial-arguments followed by arguments read from standard input. Blank lines on the standard input are ignored.
xbiff - graphical mail delivery notification utility
xcalc - simple calculator program
xclipboard - name says it all
Xconfigurator - Red Hat utility for configuring settings for X
xdm - used to start an X login session. This can be used to start a login session on a remote system. See the discussion on the following site:
- http://www.menet.umn.edu/~kaszeta/unix/xterminal/index.html
See the man pages for X, xdm, and Xserver. As usual, the man pages are pretty obscure. The best single source seems to be the Xserver man pages. After X is configured, X needs to be started at bootup with the command (in /etc/rc.d/init.d/xterm):
- X -quiet -query remotemachineaddress
If the address of a nameserver is not configured, then the numeric address of the remote machine rather than its name should be entered. If the machines are connected through ethernet cards and the net, then obviously basic networking has to be set up. Gnome and KDE come with their own versions of X display/login managers, called respectively gdm and kdm.
xdvi - view a dvi file compiled under L^AT_EX
xedit - a simple text editor for X
xf86config - graphical configuration tool for X
XF86Setup - graphical configuration tool for X
xfd - display an available font in X. Creates a grid in an x-term with one character per rectangle.
xfig - utility for interactive generation of figures
xfm - graphical file manager for X
xhost - tell X server that remote computer has access to your machine and that you will use the remote computer. This can be used to set up remote X sessions. To set up a remote X session on the UQAM Nobel machine, run the following command on the local machine (one doesn't have to be root to do this)
- xhost +nobel.si.uqam.ca
Then, log onto the remote machine using rlogin (see above) or telnet. Once logged in, use the following command to get the remote X server to open an X terminal on the local machine:
- setenv DISPLAY localhostname:0 ; xterm &
This is valid for csh, which is the default login shell on Nobel. For ksh, (and I think bash) replace with
- DISPLAY=localhostname:0
- export DISPLAY ; xterm
Other X-based programs such as Netscape or Gauss (graphical version) can also be run on a remote machine with display on the local machine with little trouble. The local X server is the program that has all of the information concerning the properties of the graphics card and terminal, so it must be necessary to have X running on the local machine. The following should also work. After using xhost to give permission to the remote machine to display on the local machine, use
- netscape -display localhostname:0.0
Question: can one start the X session on the local machine and then run a remote copy of a window manager?
xinit - start X Window. The command startx is a front end to xinit in Linux, including Slackware.
xload - displays a graphic of the system load
xlpq - graphical interface to print manager. This is included on one of the XFCE menus, but does not seem to be a part of the base Red Hat distribution.
xlsfonts - list fonts available under the X Window system.
xman - browsable command reference. Displays manual pages under X.
xmh - graphical front end under X to the nmh mail handling system. This program is part of the XFree86 package in Red Hat.
xmodmap - utility for modifying keymaps and pointer button mappings in X. Can be used to install a French Canadian keyboard. Download the Xmodmap.cf file from www.linux-quebec.org, and insert the command
- xmodmap /etc/X11/Xmodmap.cf &
into the .xession (with xdm) or the .xinitrc (with startx) file.
xosview - displays bar graphs of system load, load average, memory usage, and swap usage
xpaint - simple paint program for X
xpdf - GPL'd utility for previewing dvi files. Doesn't seem to work too well on texts with a lot of math.
xplaycd - X Window audio cd player utility
xsetroot - utility to configure root window of an X terminal
xsysinfo - graphical display of load and memory usage
xterm - start an X Window terminal session
xterm-color - color version of xterm
xv - utility for viewing and manipulating many types of image files. This is a shareware program.
xvidtune - utility for fine tuning of monitor settings under X
yacc - parser generator
ytalk - multi-user program similar to talk
zcat - read one or more files that have been compressed with gzip or compress and write to standard output
zcmp - read compressed files and pass them to cmp
zdiff - read compressed files and pass them to diff
zgrep - read compressed files and pass them to grep
Zharf - AfterStep button panel module
zip - zip utility compatible with DOS PKzip
zless - view zipped files
zmore - print contents of compressed files one screen at a time
znew - uncompress Z files and recompress in .gz format

Eventually, we want to be able to distinguish between commands that are an intrinsic part of the kernel, commands that are executable binaries that come with every distribution of Linux, executable binaries that are not provided with all distributiions of Linux, and executable shell scripts. We also want to point out the typical location of these commands on different Linux distributions.

How to Use Shell ?

2007-03-24T08:39:00.000+05:30

To use shell (You start to use your shell as soon as you log into your system) you have to simply type commands. Following is the list of common commands.

Linux Common Commands

NOTE that following commands are for New users or for Beginners only. The purpose is if you use this command you will be more familiar with your shell and secondly, you need some of these command in your Shell script. If you want to get more information or help for this command try following commands For e.g. To see help or options related with date command try
$ date --help
or To see help or options related with ls command (Here you will screen by screen help, since help of ls command is quite big that can't fit on single screen )

$ ls --help | more
Syntax: command-name --help
Syntax: man command-name
Syntax: info command-name

See what happened when you type following
$ man ls
$ info bash

NOTE: In MS-DOS, you get help by using /? clue or by typing help command as

C:\> dir /?
C:\> date /?
C:\> help time
C:\> help date
C:\> help

Introduction to Shell

2007-03-24T08:30:00.000+05:30

What's Kernel

Kernel is hart of Linux O/S. It manages resource of Linux O/S. Resources means facilities available in Linux. For eg. Facility to store data, print data on printer, memory, file management etc . Kernel decides who will use this resource, for how long and when. It runs your programs (or set up to execute binary files) It's Memory resident portion of Linux. It performance following task :-

I/O management
Process management
Device management
File management
Memory management

What's Linux Shell

Computer understand the language of 0's and 1's called binary language, In early days of computing, instruction are provided using binary language, which is difficult for all of us, to read and write. So in O/s there is special program called Shell. Shell accepts your instruction or commands in English and translate it into computers native binary language.

This is what Shell Does for US

You type Your command and shell convert it a

It's environment provided for user interaction. Shell is an command language interpreter that executes commands read from the standard input device (keyboard) or from a file.

Any of the Linux shell reads command from user (via Keyboard or Mouse) and tells Linux O/s what users want. If we are giving commands from keyboard it is called command line interface ( Usually in-front of $ prompt, This prompt is depend upon your shell and Environment that you set or by your System Administrator, therefore you may get different prompt ).
NOTE: To find your shell type following command
$ echo $SHELL