← ../

list of useful commands

adduser - used by root to add user to system

apropos - display command names based on keyword search

ar - create, modify and extract from archives

arch - print machine architecture type

as - the portable GNU assembler

awk - searches for and process patterns in a file

bash - Bourne again shell.

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.

bison - parser generator similar to yacc

bunzip2 - used to uncompress files compressed with bzip2

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

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.

cfdisk - similar to fdisk, but menu-driven

chgrp - changes group associated with file. Can be used to change the group associated with subdirectories and files of a directory.

chmod - set permissions (modes) of files or directories.

chown - changes ownership of a file. Can be used recursively.

chsh - change default shell

clear - clear screen command

cp - copies on or more files.

cpio - direct copy of files to an output device.

find - find files with many filters possible.

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.

cut - selects characters or TAB-separated fields from lines of input and writes them to standard output

date - displays or sets date and time

dd - direct copy of file from one device to another.

diff - displays differences between two files

diff3 - compares three files and reports on differences

dir - a variation of the GNU ls command that defaults to printing file names in columns

dmesg - displays messages from /var/log relative to the most recent boot

du - displays information on disk usage. The command dumpkeys - print information about the keyboard driver's translation tables to standard output

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.

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 can react automaticallu based the output of another program (written in tcl).

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

false - null command that returns an unsuccessful exit status

fc - views, edits, and executes commands for the history list. This is a shell builtin.

fg PID - bring a background or stopped process with pid ``PID'' to the foreground.

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.

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

free - gives used and free memory on system along with other useful information

fsck - file system check and repair

g++ - C++ compiler

gawk - GNU awk, mostly for processing delimited text files

gcc - invoke C, C++ compiler

getopts - parses arguments to a shell script. This is a shell builtin.

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 groupadd - create a new group on the system

groups - shows which groups you are in

grub-install - install the grub bootloader on a disk/partition

gunzip - used to uncompress files compressed with gzip

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

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

id - display userid and groupid

jobs - displays list of current jobs in the background. This is a shell builtin.

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.

last - generate a listing of user logins

lastlog - prints the last login times of all users

latex - compile a LATEX 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

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.

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

ls - list directory contents.

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.

lspnp - utility to display information about pnp devices. Part of the pcmcia or kernel-pcmcia package, depending on the distribution.

mail - sends or reads electronic mail (use bsd-mailx instead)

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.

man - displays information from online Unix reference manual

manpath - attempt to determine path to manual pages

mkdir - create a directory

mkfs - create a file system (format)

mkswap - creates a Linux swap space on the specified hard disk parition (root privileges needed)

more - list file contents, stopping after each full screen

mount - mount device in the filesystem directory tree

mount -a - mount all filesystems according to the specifications in /etc/fstab

mv - moves (renames) files

newaliases - rebuilds the /etc/aliases database used by local MTA. 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.

od - dumps contents of a file (output in octal by default)

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

ping - check if Internet computer is responding. Can also measure the time it takes the queried computer to respond.

pr - paginates files for printing

printenv - display list of environment variables

ps - displays status of processes.

pstree - display processes in the form of a tree structure.

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.

python - interpreted, interactive, object-oriented programming language

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 - reboots the system. equivalent to shutdown -r now

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.

rm - remove files or directories.

rmdir - remove empty directories

rmmod - used to remove modular device drivers

sed - edits a file (not interactively). Also a tool for processing text files.

set - set or display value of shell variables.

sh - standard UNIX shell.

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

sleep - creates process that sleeps for specified interval

sort - sorts and/or merge files

split - split file into specified number of segments

ssh - secure shell client to connect to remote servers running sshd

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

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

tar - file compression and archiving utility.

tcl - scripting language

tcsh - extended version of the C shell

tee - copy standard input to standard output and one or more files

test - evaluates an expression or compares arguments. This is a shell builtin in bash, tcsh and zsh.

tftp - user interface to TFTP protocol

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.

umount - 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.

uname - displays information about the system.

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

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

vim - improved vi editor

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

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

write - send messages to another local user

xinit - start X Window. The command startx is a front end to xinit in Linux, including Slackware.

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

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