linux commands

A

• apropos : Search Help manual pages (man -k)
• apt-get : Search for and install software packages (Debian/Ubuntu)
• aptitude : Search for and install software packages (Debian/Ubuntu)
• aspell : Spell Checker
• awk : Find and Replace text, database sort/validate/index

B

• basename : Strip directory and suffix from filenames
• bash : GNU Bourne-Again SHell
• bc : Arbitrary precision calculator language
• bg : Send to background
• break : Exit from a loop
• builtin : Run a shell builtin
• bzip2 : Compress or decompress named file(s)

C

• cal : Display a calendar
• case : Conditionally perform a command
• cat : Concatenate and print (display) the content of files
• cd : Change Directory
• cfdisk : Partition table manipulator for Linux
• chgrp : Change group ownership
• chmod : Change access permissions
• chown : Change file owner and group
• chroot : Run a command with a different root directory
• chkconfig : System services (runlevel)
• cksum : Print CRC checksum and byte counts
• clear : Clear terminal screen
• cmp : Compare two files
• comm : Compare two sorted files line by line
• command : Run a command – ignoring shell functions •
• continue : Resume the next iteration of a loop •
• cp : Copy one or more files to another location
• cron : Daemon to execute scheduled commands
• crontab : Schedule a command to run at a later time
• csplit : Split a file into context-determined pieces
• cut : Divide a file into several parts

D

• date : Display or change the date & time
• dc : Desk Calculator
• dd : Convert and copy a file, write disk headers, boot records
• ddrescue : Data recovery tool
• declare : Declare variables and give them attributes •
• df : Display free disk space
• diff : Display the differences between two files
• diff3 : Show differences among three files
• dig : DNS lookup
• dir : Briefly list directory contents
• dircolors : Colour setup for `ls’
• dirname : Convert a full pathname to just a path
• dirs : Display list of remembered directories
• dmesg : Print kernel & driver messages
• du : Estimate file space usage

E

• echo : Display message on screen •
• egrep : Search file(s) for lines that match an extended expression
• eject : Eject removable media
• enable : Enable and disable builtin shell commands •
• env : Environment variables
• ethtool : Ethernet card settings
• eval : Evaluate several commands/arguments
• exec : Execute a command
• exit : Exit the shell
• expect : Automate arbitrary applications accessed over a terminal
• expand : Convert tabs to spaces
• export : Set an environment variable
• expr : Evaluate expressions

F

• false : Do nothing, unsuccessfully
• fdformat : Low-level format a floppy disk
• fdisk : Partition table manipulator for Linux
• fg : Send job to foreground
• fgrep : Search file(s) for lines that match a fixed string
• file : Determine file type
• find : Search for files that meet a desired criteria
• fmt : Reformat paragraph text
• fold : Wrap text to fit a specified width.
• for : Expand words, and execute commands
• format : Format disks or tapes
• free : Display memory usage
• fsck : File system consistency check and repair
• ftp : File Transfer Protocol
• function : Define Function Macros
• fuser : Identify/kill the process that is accessing a file

G

• gawk : Find and Replace text within file(s)
• getopts : Parse positional parameters
• grep : Search file(s) for lines that match a given pattern
• groupadd : Add a user security group
• groupdel : Delete a group
• groupmod : Modify a group
• groups : Print group names a user is in
• gzip : Compress or decompress named file(s)

H

• hash : Remember the full pathname of a name argument
• head : Output the first part of file(s)
• help : Display help for a built-in command
• history : Command History
• hostname : Print or set system name

I

• iconv : Convert the character set of a file
• id : Print user and group id’s
• if : Conditionally perform a command
• ifconfig : Configure a network interface
• ifdown : Stop a network interface
• ifup : Start a network interface up
• import : Capture an X server screen and save the image to file
• install : Copy files and set attributes

J

• jobs : List active jobs
• join : Join lines on a common field

K

• kill : Stop a process from running
• killall : Kill processes by name

L

• less : Display output one screen at a time
• let : Perform arithmetic on shell variables
• ln : Create a symbolic link to a file
• local : Create variables
• locate : Find files
• logname : Print current login name
• logout : Exit a login shell
• look : Display lines beginning with a given string
• lpc : Line printer control program
• lpr : Off line print
• lprint : Print a file
• lprintd : Abort a print job
• lprintq : List the print queue
• lprm : Remove jobs from the print queue
• ls : List information about file(s)
• lsof : List open files

M

• make : Recompile a group of programs
• man : Help manual
• mkdir : Create new folder(s)
• mkfifo : Make FIFOs (named pipes)
• mkisofs : Create an hybrid ISO9660/JOLIET/HFS filesystem
• mknod : Make block or character special files
• more : Display output one screen at a time
• mount : Mount a file system
• mtools : Manipulate MS-DOS files
• mtr : Network diagnostics (traceroute/ping)
• mv : Move or rename files or directories
• mmv : Mass Move and rename (files)

N

• netstat : Networking information
• nice Set : the priority of a command or job
• nl Number : lines and write files
• nohup : Run a command immune to hangups
• notify-send : Send desktop notifications
• nslookup : Query Internet name servers interactively

O

• open : Open a file in its default application
• op : Operator access

P

• passwd : Modify a user password
• paste : Merge lines of files
• pathchk : Check file name portability
• ping : Test a network connection
• pkill : Stop processes from running
• popd : Restore the previous value of the current directory
• pr : Prepare files for printing
• printcap : Printer capability database
• printenv : Print environment variables
• printf : Format and print data •
• ps : Process status
• pushd : Save and then change the current directory
• pwd : Print Working Directory

Q

• quota : Display disk usage and limits
• quotacheck : Scan a file system for disk usage
• quotactl : Set disk quotas

R

• ram : ram disk device
• rcp : Copy files between two machines
• read : Read a line from standard input
• readarray : Read from stdin into an array variable
• readonly : Mark variables/functions as readonly
• reboot : Reboot the system
• rename : Rename files
• renice : Alter priority of running processes
• remsync : Synchronize remote files via email
• return : Exit a shell function
• rev : Reverse lines of a file
• rm : Remove files
• rmdir : Remove folder(s)
• rsync : Remote file copy (Synchronize file trees)

S

• screen : Multiplex terminal, run remote shells via ssh
• scp : Secure copy (remote file copy)
• sdiff : Merge two files interactively
• sed : Stream Editor
• select : Accept keyboard input
• seq : Print numeric sequences
• set: Manipulate shell variables and functions
• sftp : Secure File Transfer Program
• shift : Shift positional parameters
• shopt : Shell Options
• shutdown : Shutdown or restart linux
• sleep : Delay for a specified time
• slocate : Find files
• sort : Sort text files
• source : Run commands from a file `.’
• split : Split a file into fixed-size pieces
• ssh : Secure Shell client (remote login program)
• strace : Trace system calls and signals
• su : Substitute user identity
• sudo : Execute a command as another user
• sum : Print a checksum for a file
• suspend : Suspend execution of this shell
• symlink : Make a new name for a file
• sync : Synchronize data on disk with memory

T

• tail : Output the last part of file
• tar : Tape ARchiver
• tee : Redirect output to multiple files
• test : Evaluate a conditional expression
• time : Measure Program running time
• times : User and system times
• touch : Change file timestamps
• top : List processes running on the system
• traceroute : Trace Route to Host
• trap : Run a command when a signal is set(bourne)
• tr : Translate, squeeze, and/or delete characters
• true : Do nothing, successfully
• tsort : Topological sort
• tty : Print filename of terminal on stdin
• type : Describe a command

U

• ulimit : Limit user resources
• umask : Users file creation mask
• umount : Unmount a device
• unalias : Remove an alias
• uname : Print system information
• unexpand : Convert spaces to tabs
• uniq : Uniquify files
• units : Convert units from one scale to another
• unset : Remove variable or function names
• unshar : Unpack shell archive scripts
• until : Execute commands (until error)
• uptime : Show uptime
• useradd : Create new user account
• userdel : Delete a user account
• usermod : Modify user account
• users : List users currently logged in
• uuencode : Encode a binary file
• uudecode : Decode a file created by uuencode

V

• v : Verbosely list directory contents (`ls -l -b’)
• vdir : Verbosely list directory contents (`ls -l -b’)
• vi : Text Editor
• vmstat : Report virtual memory statistics

W

• wait : Wait for a process to complete
• watch : Execute/display a program periodically
• wc : Print byte, word, and line counts
• whereis : Search the user’s $path, man pages and source files for a program
• which : Search the user’s $path for a program file
• while : Execute commands
• who : Print all usernames currently logged in
• whoami : Print the current user id and name (`id -un’)
• wget : Retrieve web pages or files via HTTP, HTTPS or FTP
• write : Send a message to another user

x

• xargs : Execute utility, passing constructed argument list(s)
• xdg-open : Open a file or URL in the user’s preferred application.