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Linux / Unix: Quick Reference and Links

Posted by on May 20, 2010

The Utilities Down and Dirty

It should be noted that this is just a quick reference guide to some of the more common utilities.  This list is by no means all encompassing, nor inclusive.  Descriptions of the utilities are brief.  For detailed usage and information, use the man utility.

. chgrp find lpc mkfs rmdir unalias
& chmod grep lpd mkswap set unzip
adduser chown groff lpq more shutdown wall
alias chroot gzip lpr mount su who
apropos cp halt ls mv swapoff xhost +
banner dd hostname make netstat swapon xmkmf
bg env kill man passwd tail xset
bind fc less mesg ps talk zip
cat fg login mkdir pwd tar
cd file logout mkefs rm umount

. The . command tells the shell to execute all the commands in the file that are given an argument.  ie some_command
& The & placed after a command tells the shell to run that command in the background.  This allows you to keep using the shell for other commands while the background command is running, as opposed to waiting for the command to finish running in the foreground.
adduser Used by the root or other admin with
permission to create new user accounts.  It is followed by the user name.  ie

adduser johndoe

alias Used to make aliases or other names for commands.  For example, we could make the ls command similar to the DOS version with dir.

alias dir=ls

apropos A simple keyword search for the man pages.  Used in the format apropos <argument>. 
banner Prints a large banner to standard output.  If entered by itself, the user will be prompted for a single line of text.  Can also be used as follows:

banner This is a line of text.

bg Used to force a command running in the foreground to be put in the background.  While the foreground command is being run you must press the CTRL and Z key, then type bg.
bind bind is used to bind a command to a key or key sequence.  Similar to keyboard shortcuts.

bind <key or key sequence> <command>

cat lists the contents of a directory or file to standard output.
cd changes the working directory.  There are typically three different uses, as follows:

cd .. moves one directory up.

cd    moves to your home directory from any directory that you are currently in

cd directory_name            changes to that directory

chgrp Used to change the group associated with the file permissions or diectory. 

chgrp <new group> <file or directory>

chmod Change permissions associated with a file or directory.   See Unix Intermediate for detailed explanation.
chown Used to change the ownership of a file or directory.

chown <new user id> <file>

chroot Makes the root directory something other than / on the file system. 

chroot <original location> <new location>

cp Used to copy objects ( usually files ).

cp first_file second_file

dd Used to convert file formats. 

dd if=<filename> of -<location of file>

env Used to list / view the environment variables.  Used on its own without any argument.
fc Used to edit the history file
fg Used to put a background operation into the foreground.  Opposite of bg.
file Used to test arguments passed to the file.  Tests for file system, magic number, or language.
find looks for files in a directory.  Example is:

find / -name *.bin -print

grep Used to search a file or files for a particular string of text.

grep <text> <file>

groff Part of the document formatting program, calls the troff program.
gzip GNU type zip software. 

gzip <filename>

halt Used to shutdown the kernal…can only be done by root.
hostname Used to display the current host or domain name of the system.
kill Sends the term ( stop / terminate ) command to a specified process, unless a different signal is specified.

kill <option> <pid>

less Used for backward movement in a file or forward movement.  Searches files without having to read the entire file first.
login Used to login to the system
logout Used to logout of the system
lpc Used to control the operation of the line printer system. 
lpd Line printer. daemon.  Usually used at boot time it is use to search the /etc/printcap file to to find existing printers and jobs.
lpq Used to examine the spooling area of lpd for files being printed and reports on the status of print jobs.
lpr Used to print the named files.
ls Used to list the contents of a directory.
make Used to automatically determine which parts of a program need to be compiled and issued commands to compile them.
man Used to display the manual pages of a utility.

man <utility name>

mesg Used to send a message to a terminal or user for which you have permission
mkdir Used to make a directory.
mkefs Used to make an extended file system.
mkfs Used to make a Linux / Unix file system on a device. 

mkfs <filesystem>

mkswap Used to set up a swap area on a device
more Used to display one page of text at a time.  Usually used with  the pipe |

ls thisfile | more

mount Used to attach file system.  Can only be done by root.
mv Used to move an object from one location to another or to replace a file with another file
netstat Used to determine the status of a network and all the present connections
passwd Used to change your password.
ps Used to display a list of current processes. 
pwd Used to show you which directory you are in
rm Used to delete files
rmdir Used to delete directories
set Used to temporarily change a variable in the environment
shutdown Used to shutdown the system or specific areas of the system.
su Used to change user to another user.
swapoff Used to stop swaps to a file or device
swapon Used to set the access to a swap device
tail Used to display the end of a file

tail <number of lines starting at the end> <name of file>

talk Used as a chat program for another user on another terminal.
tar Used to store and extract files from an archive. 
umount Used to un-mount a file system
unalias Used to unalias a command.
unzip Used to extract files from a zip archive
wall Used to display the contents of the standard input on all terminals of all logged on users. 
who Used to display who is logged onto the system
xhost + Allows xTerms to be displayed on a system. 
xmkmf Used o create Imkaefiles for X sources.
xset Used to set option in the X Windows system
zip Used to add files to a zip archive.
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