a

• alias           Create an alias
• apropos    Search Help manual pages (man -k)

• apt-get       Search for and install software   packages (Debian)

• aspell        Spell Checker
• awk        Find and Replace text, database   sort/validate/index

b

• 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        Display the contents of a file
• 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
• 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)
• history  Command History
• hostname Print or set system name

i

• 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

• 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       Make links between files
• 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
• 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
• 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
• readonly    Mark variables/functions as readonly
• reboot     Reboot the system
• 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
• symlink     Make a new name for a file
• sync     Synchronize data on disk with memory

t

• tail     Output the last part of files
• 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)
• useradd    Create new 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

• watch    Execute/display a program periodically
• wc       Print byte, word, and line counts
• whereis    Report all known instances of a command
• which    Locate a program file in the user’s path.
• 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)
• yes      Print a string until interrupted
• .        Run a command script in the current shell
• ###      Comment / Remark

NOTE : for more details on each bash commandline, just type it in console root with –help command, e.g wget –help