Basic Linux & Unix commands

adduser ::-- Add a new user
arch ::-- Print machine architecture
awk ::-- Find and Replace text within file(s)
bc ::-- An arbitrary precision calculator language
cal ::--Display a calendar
cat ::--Concatenate files and print on the standard output
chdir ::--Change working directory
chgrp ::--Change the group ownership of files
chkconfig ::--Tool for maintaining the /etc/rc[0-6].d directory hierarchy
chmod ::--Change the access permissions of files and directories
chown ::--Change the user and group ownership of files
chroot ::--Change root directory
cksum ::--Print CRC checksum and byte counts
clear ::--Clear terminal screen
cmp ::--Compare two files
comm ::--Compare two sorted files line by line
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
date ::--Display or change the date & time
dc ::--Desk Calculator
dd ::--Data Dump - Convert and copy a file
df ::--Display free disk space
diff ::-- Display the differences between two files
diff3 ::--Show differences among three files
dir ::--Briefly list directory contents
dircolors ::-- Colour setup for `ls'
dirname ::--Convert a full pathname to just a path
du ::--Estimate file space usage
echo ::-- Display message on screen
ed ::-- A line-oriented text editor (edlin)
egrep ::--Search file(s) for lines that match an extended expression
eject ::--Eject CD-ROM
env ::-- Display, set, or remove environment variables
expand ::-- Convert tabs to spaces
expr ::-- Evaluate expressions
factor ::-- Print prime factors
false ::-- Do nothing, unsuccessfully
fdformat ::-- Low-level format a floppy disk
fdisk ::-- Partition table manipulator for Linux
fgrep ::-- Search file(s) for lines that match a fixed string
find ::-- Search for files that meet a desired criteria
fmt ::-- Reformat paragraph text
fold ::-- Wrap text to fit a specified width
format ::-- Format disks or tapes
free ::-- Display memory usage
fsck ::-- Filesystem consistency check and repair
gawk ::-- Find and Replace text within file(s)
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)
head ::-- Output the first part of file(s)
hostname ::-- Print or set system name
id ::-- Print user and group id's
info ::-- Help info
install ::-- Copy files and set attributes
join ::-- Join lines on a common field
kill ::-- Stop a process from running
less ::-- Display output one screen at a time
ln ::-- Make links between files
locate ::-- Find files
logname ::-- Print current login name
lpc ::-- Line printer control program
lpr ::-- Off line print
lprm ::-- Remove jobs from the print queue
ls ::-- List information about file(s)
man ::-- Help manual
mkdir ::-- Create new folder(s)
mkfifo ::-- Make FIFOs (named pipes)
mknod ::-- Make block or character special files
more ::-- Display output one screen at a time
mount ::-- Mount a file system
mv ::-- Move or rename files or directories
nice ::-- Set the priority of a command or job
nl ::-- Number lines and write files
nohup ::-- Run a command immune to hangups
passwd ::-- Modify a user password
paste ::-- Merge lines of files
pathchk ::-- Check file name portability
pr ::-- Convert text files for printing
Printcap ::-- Printer capability database
printenv ::-- Print environment variables
printf ::-- Format and print data
ps ::-- Process status
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
rm ::-- Remove files
rmdir Remove folder(s)
rpm ::-- Remote Package Manager
rsync ::-- Remote file copy (Synchronize file trees)
screen ::-- Terminal window manager
sdiff ::-- Merge two files interactively
sed ::-- Stream Editor
select ::-- Accept keyboard input
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
symlink ::-- Make a new name for a file
sync ::-- Synchronize data on disk with memory
tac ::-- Concatenate and write files in reverse
tail ::-- Output the last part of files
tar ::-- Tape Archiver
tee ::-- Redirect output to multiple files
test ::-- Evaluate a conditional expression
time ::-- Measure Program Resource Use
touch ::-- Change file timestamps
top ::-- List processes running on the system
traceroute ::-- Trace Route to Host
tr ::-- Translate, squeeze, and/or delete characters
true ::-- Do nothing, successfully
tsort ::-- Topological sort
tty ::-- Print filename of terminal on stdin
umount ::-- Unmount a device
uname ::-- Print system information
unexpand ::-- Convert spaces to tabs
uniq ::-- Uniquify files
units ::-- Convert units from one scale to another
unshar ::-- Unpack shell archive scripts
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
vdir ::-- Verbosely list directory contents (`ls -l -b')
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
who ::-- Print all usernames currently logged in
whoami ::-- Print the current user name
xargs ::-- Execute utility, passing constructed argument list(s)
yes ::-- Print a string until interrupted