useful command tools in linux



Frequently Used Ones:
aliasCreate an alias
cal– Display a calendar
case– Conditionally perform a command cat Display the contents of a file
catDisplay the contents of a file (concatenate)
cdChange Directory – change the current working directory to a specific Folder.
chgrp– Change group ownership
chmod– Change access permissions
chown– Change file owner and group
cmpCompare two files
comm– Compare two sorted files line by line
continue– Resume the next iteration of a loop
cp Copy one or more files to another location
crontab– Schedule a command to run at a later time
cutDivide a file into several parts
date– Display or change the date & time
dd– Dump Data – convert and copy a file (use for RAW storage)
dfDisplay free disk space
diffDisplay the differences between two files
diff3Show differences among three files.
dir– Briefly list of directory contents
du– Estimate file space usage, reports the amount of disk space used by the specified files and for each subdirectory.
echo Display message on screen
export– Set an environment variable
expr– Evaluate expressions
fdisk– Partition table manipulator for Linux
findSearch a folder hierarchy for filename(s) that meet a desired criteria
fsck– Filesystem consistency check and repair
headOutput the first part of files, prints the first part (10 lines by default)
history– Command Line history
hostname– Print or set system name
id– Print real and effective user id (uid) and group id (gid)
join– Join lines on a common field
killStop a process from running
less– Display output one screen at a time, Search through output, Edit the command line.
ln– Make links between files
locate– Find files
logout– Exit a login shell
lpr– off line print – sends a print job to the default system queue
lprm– Remove jobs from the line printer spooling queue
ls– List information about FILEs, by default the current directory.
manDisplay helpful information about commands.
mkdir– Create new folder(s), if they do not already exist
more– Display output one screen at a time
mount– Mount a file system
nice– Run a command with modified scheduling priority
passwd– Modify a user password
pasteMerge lines of files
pr– Print files, printing and pagination filter for text files
printf– Format and print data
psProcess status, information about processes running in memory
pwd– Print Working Directory
rcp– Copy files between two machines
rm– Remove files (delete/unlink)
rmdir– Remove folder(s), if they are empty
rsyncRemote file copy (Synchronize file trees)
sedStream Editor
seq– Print numeric sequences
shutdown– Shutdown or restart linux
sleep– Delay for a specified time
sort– Sort text files
split– Split a file into fixed-size pieces
su– Substitute user identity
sum– Print a checksum for a file
tac– Concatenate and write files in reverse
tailOutput the last part of files
tarTape Archiver
time– Measure Program Resource Use
top– List processes running on the system
touch– Change file timestamps
uname– Print system information
uniq Uniquify files
useradd– Create new user account
usermod– Modify user account
users– List users currently logged in
wc Print byte, word, and line counts
which– Locate a program file in the user’s path.
who– Print who is currently logged in
xargs– Execute utility, passing constructed argument list(s).

The full list
aliasCreate an alias
break– Exit from a loop
builtin– Run a shell builtin, passing it args, and return
cal– Display a calendar
case– Conditionally perform a command cat Display the contents of a file
catDisplay the contents of a file (concatenate)
cdChange Directory – change the current working directory to a specific Folder.
cfdisk– Curses based disk 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
cksum– Print CRC checksum and byte counts
cmpCompare two files
comm– Compare two sorted files line by line
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
cutDivide a file into several parts
date– Display or change the date & time
dc– Desk Calculator
dd– Dump Data – convert and copy a file (use for RAW storage)
declare– Declare variables and give them attributes
dfDisplay free disk space
diffDisplay the differences between two files
diff3Show differences among three files.
dir– Briefly list of directory contents
dircolors– Color setup for `ls’, outputs a sequence of shell commands to set up the terminal for color output from `ls’ (and `dir’, etc.).
dirname– Convert a full pathname to just a path
dirs– Display the list of currently remembered directories.
du– Estimate file space usage, reports the amount of disk space used by the specified files and for each subdirectory.
echo Display message on screen
egrep– Search file(s) for lines that match an extended expression
enable– Enable and disable builtin shell commands.
env– Display, set, or remove environment variables, Run a command in a modified environment.
eval– Evaluate several commands/arguments
exec– Execute a command
expand– Convert tabs to spaces
export– Set an environment variable
expr– Evaluate expressions
factor– Print prime factors
false– Do nothing, returning a non-zero (false) exit status
fdformat– Low level format a floppy disk
fdisk– Partition table manipulator for Linux
fgrep– Search input files for lines that match a given pattern
findSearch a folder hierarchy for filename(s) that meet a desired criteria
fmt– reformats the paragraphs in the given files.
fold– Wrap text to fit a specified width
for– Expand words, and execute commands
fsck– Filesystem consistency check and repair
function– Define Function Macros
getopts– Parse positional parameters
hash– Remember the full pathname of a name argument
hashcharacter– A comment or remark is indicated by starting the line with the # character
headOutput the first part of files, prints the first part (10 lines by default)
history– Command Line history
hostname– Print or set system name
id– Print real and effective user id (uid) and group id (gid)
if– Conditionally perform a command.
import– Capture some or all of an X server screen and save the image to file
install– copy files while setting their permission modes and, if possible, their owner and group
join– Join lines on a common field
killStop a process from running
less– Display output one screen at a time, Search through output, Edit the command line.
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
lpc– Line printer control program
lpr– off line print – sends a print job to the default system queue
lprm– Remove jobs from the line printer spooling queue
ls– List information about FILEs, by default the current directory.
m4– macro processor
manDisplay helpful information about commands.
mbadblocks– Check and repair floppy disk problems
mkdir– Create new folder(s), if they do not already exist
mkfifo– Make FIFOs (named pipes) with the specified names.
mknod– creates a FIFO, character special file, or block special file
more– Display output one screen at a time
mount– Mount a file system
mtools– allow Unix systems to manipulate MS-DOS files
mvMove or rename files or directories
nice– Run a command with modified scheduling priority
nl– Number lines and write files
nohup– Run a command immune to hangups, runs the given COMMAND with hangup
passwd– Modify a user password
pasteMerge lines of files
period– source or dot operator
popd– Remove the top entry from the directory stack
pr– Print files, printing and pagination filter for text files
printf– Format and print data
psProcess status, information about processes running in memory
pushd– Save and then change the current directory. With no arguments
pwd– Print Working Directory
quota– Display disk usage and limits
quotacheck– Scan a file system for disk usage
quotactl– Set disk quotas
ram– ram disk device
rcp– Copy files between two machines
read– Read a line from standard input
readonly– Mark variables/functions as readonly
return– Cause a shell function to exit with the return value n
rm– Remove files (delete/unlink)
rmdir– Remove folder(s), if they are empty
rsyncRemote file copy (Synchronize file trees)
Run– Run a command – ignoring shell functions
sdiff– Merge two files interactively
sedStream Editor
select– Accept keyboard input
seq– Print numeric sequences
set– Manipulate shell variables and functions
shift– Shift positional parameters
shopt– Shell Options
shutdown– Shutdown or restart linux
sleep– Delay for a specified time
sort– Sort text files
split– Split a file into fixed-size pieces
su– Substitute user identity
sum– Print a checksum for a file
symlink– Make a new name for a file
sync– Synchronize data on disk with memory
tac– Concatenate and write files in reverse
tailOutput the last part of files
tarTape Archiver
tee– Redirect output to multiple files
Test– Evaluate a conditional expression
time– Measure Program Resource Use
times – Print out the user and system times used by the shell and its children
top– List processes running on the system
touch– Change file timestamps
tr– Translate, squeeze, and/or delete characters
traceroute– Trace Route to Host
true– Do nothing, successfully
tsort– Topological sort
tty– Print filename of terminal on stdin
Type– Describe a command
ulimit– Limit user resources
umask– Users file creation mask
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
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 who is currently logged in
xargs– Execute utility, passing constructed argument list(s).
yes– prints the command line arguments, separated by spaces and followed by a new line

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