Basic UNIX Commands

Introduction

The basic form of any UNIX command is: command_name options argument(s)

Unix is case-sensitive.
Unix distinguishes between upper and lower case letters in the names of files and programs. Thus, while ls is a valid Unix command, LS is not.
Login names and passwords are also case-sensitive.
A filename in Unix can consist of any combination of characters on the keyboard except for the space bar and all of the following : * ? ! \ \ ‘ “ > ; , ^ ( ) $ ~. These characters cannot be used in filenames because they have special meaning to the shell. For instance, the first two characters are used as “wildcards”.
Some programs, such as Pico, have their own commands that you type within the program rather than at the Unix shell prompt. The Shell prompt reappears whenever you exit those programs.

Task	Command	Notes
Lists your files	ls	Available options: -l (long format) -a (view all files, including hidden ones)
Change to a directory.	cd DirName	Use "cd .." to change to the parent directory.
See the full path for the current directory.	pwd

Task	Command	Notes
Move a file into a different directory, or rename the file.	mv file1 file2	If moving a file to a new directory, the full path to that directory is needed. Example: mv file1 $SCRATCH/NewDir Note: In the above case, if you do not wish to rename the file, you do not need to add a filename, the directory name is sufficient.
Copy a file	cp file1 file2	To copy a directory, use the -r option
Removes a file.	rm filename	Preferably use rm -i which will ask you for confirmation before deleting the file
Tells you how many lines, words, and characters there are in a file	wc filename
Lets you change the read, write, and execute permissions on your files. chmod o+r filename will make the file readable for everyone, and chmod o-r filename will make it unreadable for others.	chmod option file -->
Make a new directory	mkdir DirName

Task	Command
Display a file.	cat filename
View a file one page at a time. Press [space-bar] if you want to see another page, type [q] if you want to quit reading, or [b] to go back a page.	less filename
View the first ten lines of a file. Use the -N option where N is a positive nonzero integer to specify the number of lines to display.	head filename
View the last ten lines of a file. Use the -N option where N is a positive nonzero integer to specify the number of lines to display.	tail filename
Searching for a keyword in a file using less	less filename /keyword
Search for all lines containing a keyword in a given file. Use the -i option to ignore upper/lower case distinctions. To search for a phrase, you must enclose the phrase with single quotes.	grep keyword filename

Task	Command
List your processes. Contains information such as the process ID, which you might need to kill a particular process which would be creating difficulties on your computer	ps -u yourusername
Ends the process, whose process ID you typed in.	kill processID
Show what your disk quota is, how much you're using, and incase you have exceeded your quota.	quota -v
Shows the disk usage of the files and the directories in filename, du -sk will give a total of all files and directories on the disk.	du filename
Lists your last logins.	last yourusername
Gives you lots of information about that user, e.g. when they last read their mail and whether they're logged in.	finger username
Tells you who's logged in, and what they're doing.	w
Tells you who's logged on, and which computer they are logged on to.	who

Task	Command
Shows the current date and time	date
Shows a calendar of the current month. If you type in cal 10 1995 you will get the calendar for the month of October in the year 1995.	cal
Shows you the manual page for the command	man commandname
Refreshes or clears your screen.	clear OR Ctrl + l
Stops running program or the command	Ctrl + c
Suspends the currently running program or command	Ctrl + z
Ends your login session	exit OR logout