• Words in monospace type are commands and should be typed as they are printed
• Words in bold type should be substituted with the appropriate filename or directory
• Unix is case-sensitive — UPPER and lower case letters have different meanings

General

man command

Display the Unix manual entry describing a given command

apropos command

Locate commands by keyword

alias name1 name2

Create command alias name

alias name

Display command alias

unalias name

Remove command alias name

passwd

Change password

quota

Display amount of disk space used

df

Show available system disk space

du

Show disk space being used up by folders

bc

Basic calculator

bc
obase=16
255

Displays FF

bc
ibase=16
obase=10

Hex to Dec

date

Display date & time

cal month year

Show calendar

whoami

Display current user

history

Display recent commands

!!

Repeat last shell command

!string

Repeat last shell command that began with string

! n

Repeat recent shell command n

Ctrl-p (previous)

Move up in history list

Ctrl-n (next)

Move down in history list

Ctrl-b (backwards)

Cursor left to edit command

Ctrl-f (forwards)

Cursor right to edit command

Ctrl-d (delete)

Delete character in command

clear

Clear terminal screen

lock

Lock terminal

reset

Reset / initialize terminal

set

Show environment

env

Show current settings

sentenv name v

Set env var to value v (csh/tcsh)

export name="v"

Set environment variable to value v (ksh/bash)

exit

Terminate current session

script

Make a typescript of everything printed on the terminal

sudo /usr/libexec/locate.updatedb

Update the locate database

File System Navigation

*

Wild card: match zero or more characters

?

Wild card: match zero or one character

.

Shorthand for the current directory

..

Shorthand for the parent of the current directory

~

Home directory

~username

Home directory of user username

cd dir

Change to directory dir

cd

Return to home directory

pwd

Display working directory

file file

Determine file type

du -ks *|sort -nr|more

Show all the directory sizes in order, largest first

ls

List the contents of the current directory

ls dir

List the contents of the directory dir

ls -l

Show permissions, owner, size, and other file info

ls -a

Show all files, including (hidden) files that begin with a dot

ls -R

Show files recursively, for all subdirectories

ls -d

List directories like other files, without displaying their contents

ls -k

List file sizes in kilobytes

ls -X

Sort files by file extension

ls -1

Display the listing in 1 column

ls -t

Show files in time order, newest to oldest

ls -l | grep "^d"

List all directories in the current directory without any of the files

ls -l | grep ^d | wc -l

Find the number of subdirectories in the current directory

ls -ls|sort -nr|more

List files by size, largest first

Data Manipulation

mkdir dir

Create new directory dir

cp file1 file2

Copy file(s)

cp file dir

Copy file(s) into a directory

cp -r dir1 dir2

Copy a directory and, recursively, its subdirectories

mv file dir

Move file to directory dir

mv dir1 dir2

If directory dir2 exists, move dir1 into dir2; otherwise, rename dir1 as dir2

mv file1 file2

Rename file1 as file2

#!/bin/sh
for i in *
do
echo $i
mv $i `basename $i`.ext
done

Rename a number of files

rm file

Remove file

rm -f file

Force, remove files without prompting

rm -r file

Remove files, directories, and recursively, any subdirectories

rmdir dir

Remove empty directory dir

vi file

Vi fullscreen editor

emacs file

Emacs fullscreen editor

pico file

Pico text editor

wc file

Count lines, words, & chars

cat file

List contents of file

more file

Display contents of a file one screen at a time

less file

Opposite of more

head -n file

Display first n lines of file

tail -n file

Display last n lines of file

cmp file1 file2

Compare two files

diff file1 file2

Show file differences

cp file1 file2

Copy file file1 into file2

sort file

Display the lines of text file alphabetically

sort -r file

Sort in reverse order

sort -n file

Sort numerically (2 before 10)

sort +n file

Sort on n+1^st field

cat file1 file2 > file3

Concatenate file1 & file2 into file3

split [-n] file

Split file into n-line pieces

grep sample file

Output lines that match sample string or pattern

grep -i

Case-insensitive search

grep -n

Show the line # along with the matched line

grep -v

Invert match: find all lines that do not match

grep -w

Match entire words, rather than substrings

touch file

Update the timestamp on a file, if the file doesn't exist, touch creates an empty file

I/O Redirection

The shell expects input from; and sends output to, a terminal. To write command output to files or read input from files, redirection is used. UNIX defines three I/O units with corresponding file descriptors:

0: stdin (standard input)

1: stdout (standard output)

2: stderr (standard error)

prog > file

Redirect (write) stdout of prog to file

prog >> file

Append stdout of prog to file

prog < file

Read stdin for prog from file

prog <file1 >file2

Read stdin for prog from file1, redirect stdout to file2

prog 2>file

Write stderr of prog to file

prog 2>&1

With file descriptor: write stderr of prog to stdout

cmd1 | cmd2

Pipeline: use cmd1’s output as input for cmd2

cmd1 && cmd2

cmd2 is executed only if the execution of cmd1 ends up successfully

cmd1 || cmd2

cmd2 is executed only if the execution of cmd1 does not end up successfully

cmd1 ; cmd2

Execute cmd2 after execution of cmd1 stopped

nohup command < file.in >> file.out&

"No hangup": execution of command will continue even if the user logs off the system (exit). Run command in the background (&), taking input from file.in and appending output to file.out.

Permissions

-rwxr-xr-x

Directories have a d in the first column; regular files have a —.

The remaining 9 characters indicate the owner, group, and world permissions of the file.

An r indicates that the file is readable; w is writable, and x is executable.

A dash in the column instead of a letter means that particular permission is turned off.

t is the "sticky bit" for directories; prevents files from being deleted by anyone other than the owner.

s is the "setuid-bit" for files; execute a program using the owner’s permissions (rather than those of the one who calls it).

Setting Permissions with Letters

chmod u+rwx,go+rx file

u is the user's (owner) permissions; g is the group permissions, and o is world (other) permissions.

The + sign turns the stated permissions on; a — sign turns them off.

Directories should always have, at least for the owner, the x permission set.

A directory doesn't have to be readable for the web server to read and execute files within that directory. Only the files themselves must be readable.

Numeric Permissions

chmod 711 file

Change permissions on a file

The first number translates to permissions by the owner (logon account).

The second is permissions for the group (a possibly empty group of logon accounts).

The third is permissions for everyone.

0

--- (no permissions)

1

--x (executable only)

2

-w- (writable only)

3

-wx (writable and executable)

4

r--- (readable only)

5

r-x (readable and executable)

6

rw- (readable and writable)

7

rwx (readable, writable, and executable)

File Compression

compress file

Reduce the size of a file

uncompress file

Restore a compressed file

tar cf - /home/file | compress > file.tar.Z

tar and compress a file

tar cf - /home/file | gzip > file.tar.Z

tar and gzip a file

ls -al | awk '$0!~/^d/ {print $9}' | xargs tar cvf archive_name.tar

Archive only regular files in a directory, ommitting subdirectories and hidden files

Make an index file of the contents of the tar file

tar cvf - /home/file 2>file.idx | compress > file.tar.Z

For sh, ksh

(tar cvf - /home/file | compress > /file.tar.Z) >&file.idx

For csh

A simple backup script

tar cvf - /home/file 2>file.idx | gzip > home/file.tar.Z

sh:

% pico ~/bin/backup.sh
#!/bin/sh
echo "Backup of Folder:"
tar cvf - /home/file 2>file.idx | gzip > home/file.tar.Z

Save the script in ~/bin

% chmod +x ~/bin/backup.sh

Make it executable

% rehash

Force the shell to rebuild its list of known executables

Networking & Communications

who

List logged in users

finger user

Display user information

chfn

Change finger information

ping host

Send ICMP ECHO_REQUEST packets to network hosts

telnet hostname

Connect to another remote system using the telnet protocol

ssh host

rsh host

Log into and execute commands on a remote machine

lpr -P printer file

Output file file to line printer

mail user

Send mail to user

biff y/n

Instant notification of mail

Process Control

sleep n

Sleep for n seconds

jobs

Display list of jobs

Ctrl-c

Interrupt process / stop execution of a command

Ctrl-d

End of typed input (End of File Key)

Ctrl-q

Start / resume terminal output

Ctrl-s

Stop terminal output

Ctrl-z

Suspend execution of a command

ps

Show process status statistics

ps aux

Show complete process listing

top

Show system usage statistics dynamically; stop with q

kill -9 n

Remove process n

stop %n

Suspend background job n

command&

Run command in background

bg %n

Resume background job n

fg %n

Resume foreground job n