alias : Create an alias
awk : Find and Replace text within file(s)

break : Exit from a loop
builtin : Run a shell builtin

cal : Display a calendar
case : Conditionally perform a command
cat : Display the contents of a file
cd : Change Directory
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
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

date : Display or change the date & time
dc : Desk Calculator
dd : Data Dump - Convert and copy a file
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
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
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
enable : Enable and disable builtin shell commands
env : Display, set, or remove environment variables
eval : Evaluate several commands/arguments
exec : Execute a command
exit : Exit the shell
expand : Convert tabs to spaces
export : Set an environment variable
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.
for : Expand words, and execute commands
format : Format disks or tapes
free : Display memory usage
fsck : Filesystem consistency check and repair.
function : Define Function Macros

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)

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

id : Print user and group id's
if : Conditionally perform a command
import : Capture an X server screen and save the image to file
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
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
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)

m4 : Macro processor
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
mtools : Manipulate MS-DOS files
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
popd : Restore the previous value of the current directory
pr : Convert text 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

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
remsync : Synchronize remote files via email
return : Exit a shell function
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
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
source : Run commands from a file `.'
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
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

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 : Verbosely list directory contents (`ls -l -b')
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.
while : Execute commands
who : Print all usernames currently logged in
whoami : Print the current user id and name (`id -un')

xargs : Execute utility, passing constructed argument list(s)
yes : Print a string until interrupted

. : Period, Run commands from a file
# : Comment / Remark