linux command from a to z

apropos	Search Help manual pages (man -k)
apt-get	Search for and install software packages (Debian)
aptitude	Search for and install software packages (Debian)
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 files
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 and 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 files 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 files 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 files
getopts	Parse positional parameters
grep	Search files 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 files
H
hash	Remember the full pathname of a name argument
head	Output the first part of files
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 files
lsof	List open files
M
make	Recompile a group of programs
man	Help manual
mkdir	Create new folders
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 folders
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
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 lists
xdg-open	Open a file or URL in the user’s preferred application
Y
yes	Print a string until interrupted