General Unix Commands -Very Useful

Command	Action	Example
alias	Creates a temporary name for a Unix command.	alias   name command
	To remove an alias:	unalias   name
ansiprint	Prints a file to a printer connected to your computer.	ansiprint   file
assets	Displays your account resources, use, and threshold.
bg	Places a suspended job in the background.
cat	Displays a specified file.	cat   file
cd	Changes current directory to a different directory.	cd   directory
	To change back to your home directory:	cd
	Directory abbreviations: ~     Home directory ..     Parent directory .       Current working directory
chmod	Changes permission status for a file or directory.	chmod   code file chmod   code directory
	To keep a file private:	chmod   600 file
	To give everyone read permission:	chmod   664 file
compress	Reduces the size of a file and adds .Z to the file's name.	compress   file
	To restore a compressed file:	uncompress   file.Z
cp	Makes a copy of a file.	cp   file1 file2
	To copy a file into a different directory:	cp   file directory
	To inquire before overwriting an existing file:	cp -i   file1 file2
diff	Compares two files and displays the differences.
fg	Restarts a suspended job in the foreground.
finger	Displays user information at the specified computer.	finger   userid@computer
	To change your finger entry information:	chfn
ftp	Starts the file transfer program with a remote computer.	ftp   address
grep	Finds lines in a file matching a character pattern.	grep -icvn   pattern file
	-i     Ignores case -c     Lists count of lines that contain pattern -v     Lists all lines except those with pattern -n     Lists line number for each found pattern
head	Displays the first ten lines of a file.	head   file
	To display the first n number of lines:	head -n   file
help	Displays an online help note.	help   note
	To display a list of help notes:	help -l
history	Displays a list of your most recent commands.	history
	To repeat the nth command from the list:	!   n
	To repeat your most recent command:	!!
jobs	Displays active jobs and their corresponding job numbers.	jobs
	To start a job in the background:	job   &
	To return a job to the foreground by the job number:	fg   %number
	To send a running job to the background:	z bg
kill	Terminates a process by its process identification number.	kill   pid
	To use the strongest form of the kill command:	kill -9   pid
logout	Ends your computer session.
ls	Lists the files and subdirectories in your current directory.	ls -Fltra
	-l     Lists long format -t     Lists by modification time -r     Lists in reverse order -F     Lists file type with special character -a     Lists all files including dot (.) files
lynx	Starts a text-only Web browser session	lynx
	Starts a Web browser session at a specific Web address.	lynx   url
man	Displays Unix Manual entry for a command.	man   command
	To search Manual Index for a keyword or topic:	man -k   keyword
mesg	Displays your talk and write message access status.	mesg
	To set your message status to yes or no:	mesg y (or n)
mkdir	Creates a new directory within your current directory.	mkdir   directory
more	Displays a file one screen at a time.	more   file
	Use to scroll forward and q to quit.
mv	Moves a file to a different directory.	mv   file directory
	Moves a directory to a second directory.	mv   directory1 directory2
	To rename file1 as file2:	mv   file1 file2
	To rename directory1 as directory2:	mv   directory1 directory2
	To inquire before overwriting an existing file:	mv -i   file1 file2
passwd	Starts program to change account password.
pico	Starts the Pico text editor with a file.	pico   file
pine	Starts the Pine® electronic mail program.
ps	Displays processes and their corresponding process identification numbers.
pwd	Displays absolute pathname of current directory.
rm	Permanently deletes a file.	rm   file
	To verify prior to removal:	rm -i   file
rmdir	Deletes an empty directory.	rmdir   directory
	To verify prior to removal:	rmdir -i   directory
spell	Checks the spelling in a file.	spell   file
telnet	Starts a telnet session with a remote computer.	telnet   address
vi	Starts the vi text editor with a file.	vi   file
w	Displays a list of who is on system.
wc	Counts lines, words, and characters in a file.	wc   file

Special commands and characters:

Redirection :

	<	Routes input to command from file
	>	Routes output from command to file
	>>	Appends output to existing file
	|	Routes output between commands

Wildcards used in filenames :

	*	Matches any number of characters
	?	Matches one character

Control codes :

	s	Suspends the screen display
	q	Restarts suspended display
	d	Signals end of file
	c	Cancels a command
	z	Suspends a process or job: use fg to restart
	u	Clears the command line

FILE COMMANDS:

 
Touch Create a new file.
Usage: touch FileName
 

cp Copy files.
Usage: cp [options] FileName1 File Name2

cp [options]
Options: -r recursively copy directory structures.
 

mv Move or Rename files or directories.
Usage: mv [options] file1 ./tmp/file1
mv [options]
Options: -i query user for confirmation.
 

rm Remove files.
Usage: rm [options] filename
Options: -r recursively remove directory structures.
-i query user for confirmation.
 

cat View complete file content.
cat
 

more View file contents in sections determined by the size of the terminal.
Usage: more
 

less View file contents in sections determined by the size of the terminal.
Has more options and search features than more.
Usage: less [options]
 

compress Reduces the size of the file. and adds the extension .Z
Usage: compress .
 

uncompress /zcat :  Restores a compressed file.
Usage: uncompress
Usage: zcat

 

DIRECTORY COMMANDS
cd Change directory.
Usage: cd
Eg: cd my-directory
cd go to home directory
cd .. go up one directory
 

pwd Print working directory on the terminal.
 

ls List the content of a directory.
Usage: ls [options] or ls [options]
Options: -l list all files in long format.
(permissions, users, filesize,date, and time are displayed).
-a list all files including those beginning with a “.”
-F list files distinguishing
directories/ executables* symbolic links@
-R recursively list subdirectories encountered.
 

mkdir Create a new directory.
Usage: mkdir
 

rmdir Remove a directory if its empty.
Usage: rmdir
 

SYMBOLIC LINKS
ln Create symbolic links between files or between directories.
Usage: ln [options]
ln [options]
Options: -s allows linking across file systems and allows the display
of the link’s name upon ls -l.
Eg: ln -s course-file myfile
Eg: ln -s course-directory myspace

 

TERMINAL COMMANDS
clear Clears the terminal.
 

echo: Write a string to standard output.
Usage: echo “string” or
echo ‘string’
 

repeat Repeats commands.
Usage: repeat
 

HELP COMMANDS
man Displays the manual page for the selected command.
Usage: man

rtfm Displays the man page and help files ont he terminal.
Usage: rtfm
 

INFORMATION COMMANDS
history Lists the commands typed during the session.
Options: -r displays the list in reverse.
 

hostname Displays the computer’s or server’s name on the terminal.
who Displays who is on the system.
who am i Displays the invoking user.