Linux Commands

Commands

Linux Commands

**Console Commands**
Utility or Command	Use/Description
passwd	Changes password
nslookup	Queries Internet domain name servers
quota	Displays disk usage and limits
motd	Message of the Day
finger username	User information lookup program
man or xman command	Displays pages of online manual
xman	Displays System Manual in X
less filename or more filename	Displays the contents of a file in the terminal one page at a time
info	Displays information and documentation on shells, utilities and programs
clear	Clears the terminal window
ls directory	List contents of a directory
cat filename	Displays the contents of a file in the terminal
rm filename	Removes a file
pico filename or emacs filename	Opens and edits text files
cp sourcefile detstinationfilename	Copies a file
lpr filename	Sends file to printer
grep string filename	looks through files for strings
head filename	Displays first 10 lines of file
tail filename	Displays last 10 lines of file
mv existingfilename newfilename	Moves or renames file
lpq filename	Displays files in printing queue
lprm filename	Removes file from printing queue
sort filename	Displays and sorts file contents
diff filename1 filename2	Displays differences between files
file filename	Displays information about file contents
echo string	Copies string to terminal
date	Displays current date and time
cal	Displays calendar
gzip filename	Compresses a file
compress filename	Compresses a file
gunzip filename	Decompresses a compressed file
zcat filename	Displays contents of a compressed file
apropos command	Lists all man page titles/headers that contain the command
lynx	Text based web browser
dmesg	Displays kernel ring buffer
which command	Displays path to command
whereis command	Displays paths to locations of commands
who	Lists currently logged on users
finger username@hostname	Obtains detailed information about a user currently using the system
w	Lists currently logged on users with processing usage
mesg y/n	Sets options for letting other users write you messages
write user	Sends message to other users
talk user	Allows two way chat to other users
chmod permissions filename	Changes file access permissions
mkdir directoryname	Makes a directory
rmdir directoryname	Removes an empty directory
ln existingfile new-link	Creates link to an existing file (hard link)
stat filename	Lists information about a file
ln -s existingfile new-link	Creates link to an existing file (soft link)
df	Displays all mounted filesystems
ps	Reports process status
command &	Sends a job to the background (job: one or more commands connected by a pipe "\|" or pipes) The operating system assigns a number to the job when you press return. example: `[1] 3578`
top	Displays updating list of currently running processes
tty	Displays the name of the terminal in which the command was issued
command > filename	Redirects standard output
command < filename	Redirects standard input
*cat* file1 >> file2	Appends standard output from file1 to file2
*cat* /dev/null > filename or filename > /dev/null	Redirects "bit bucket" or null string to file (only superuser has write access to this file)
command1 \| command2	Pipe sends standard output of one command to the standard input of another command
tr string1 string2 < inputfile	Translates each character in string1 to the corresponding character in string2
command \| tee filename \| grep* string*	Sends the output of one command to standard output and a file
bg %job number	Sends job to the background by job number
fg %job number	Brings job to the foreground by job number
kill PID or %job number	Aborts a process by PID (Process Identification Number) or job number
jobs	Displays a list of current jobs
netcfg	Utility to set up PPP and network configurations
xev	Utility used to see information flow from X server to client
echo $DISPLAY	Environment variable that displays the ID string for a window
echo $PATH	Variable that displays executable path
netstat	Displays network connections
viewres	Graphical class browser for X
xbill	Game featuring Bill Gates trying to put windows on Macs and NeXT workstations
xevil	Game similar to Loderunner?
xchomp	Linux's version of PacMan
xcmap	Strange color lookup utility
xedit	Text editor for X
asclock	Clock from AfterStep
xconsole	Strange console for X
xmessage message	Sends message to a dialog box
xgal	XGalaga game
xg3	Image viewing program
xgc	Graphing calculator?
xjewel	Jewel game for Linux
xkbvleds	LEDs?
xkbwatch	LEDs?
xlogo	Displays X logo
xmixer	Opens system sound controls
xsnow	Snowflakes are fallin' on your desktop
xwininfo	Displays info about a window
startx	Starts an X Window System server
ghostview	Starts a text preview application
xv filename	Image viewer
xsetroot -color	Set background color in X
xcalc	Starts a calculator in X
xclipboard	Starts a clipboard in X
traceroute host	Prints the route packets take to the host
hostname	Displays system identity name
rlogin host	Utility to connect to a remote system
telnet host	Utility to connect to a remote system (similar to rlogin but more interactive)
rcp file remotemachine	Used to copy from a remote computer
ftp	Utility to transfer files between systems on a network
rsh command	Utility to run a command on a remote system without logging in
ping host	Utility used to test connection to a remote system
lcd directorypath	Changes local machine directory while logged on to remote machine

**Shared Directories**
Directory	Description
/	Root - The root directory is present in all Linux system file structures. It's the parent of all files in the system.
/bin	Essential common binaries - Holds files needed to boot the system and run it when it comes up in single user mode.
/boot	Static files of the boot loader.
/dev	Device files - All files that represent peripheral devices.
/etc	Machine-local system configuration - Holds administrative, config, and other system files. Holds /etc/passwd file that contains a list of all users who have permission to the system.
/home	User home directories - Contains each user's or client's home directory
/lib	Shared libraries
/mnt	Mount point for temporary partitions
/proc	Kernel and process information (virtual filesystem)
/root	Home directory for root
/sbin	Essential system binaries - Contains utilities for system administration.
/tmp	Temporary files
/usr	Second major hierarchy - Includes subdirectories that contain information used by the system.
/var	Variable data - Contains files whose contents change as system runs.

**vi Commands**
Command	Description
vi filename	Starts vi and creates a new file
:q!	Quits vi without saving work
p	Pastes data in buffer below current line
P	Pastes data in buffer above current line
yy	Copies current line
:r !command	Reads in output of the command
i	Puts vi in insert mode
:set autoindent	Sets vi to indent automatically
:set showmatch	Sets vi to show matching parenthesis
:set nu	Sets vi to display line numbers
:set showmode	Sets vi to display the mode you're in
ESCAPE	Sets vi to command mode
CONTROL-U	Erases current line (insert mode)
CONTROL-H	Erases on letter (insert mode)
CONTROL-W	Erases current word (insert mode)
h, j, k, l	Moves cursor left, up, down, right respectively
u	Undoes last action
x	Deletes a single character
dw	Deletes a single word
dd	Deletes a single line
ZZ	Writes work buffer to disk and exits vi
o	inserts line after cursor position
CONTROL-L	Redraws screen
:w filename	Save work as filename and exits

**Control Characters**
Key	Use
CONTROL-H or BACKSPACE	Erases a character on the command line
CONTROL-U	Deletes an entire command line
CONTROL-W	Erases a word on the command line
CONTROL-C	Aborts program execution
COMMAND-Tab	Switches Programs
CONTROL-L or CONTROL-R	Refreshes the screen
Control-D, logout or exit	Logs you off the system