A handful of useful Unix commands 

The following are a collection of commonly used Unix 
commands, which students have found useful when dealing 
with a Unix system or server. This is not a complete list 
of the commands, nor is it designed to comprehensively 
cover each command. Rather, it will allow the new Unix user 
to function in a Unix environment as they learn their way 
around. (Optional usage is shown in square brackets [] .) 
The format of this page is:

Command 		Function 
Example 		Explanation 

ls 		List the files in the current directory. 
ls 		Show me the files in the directory I am currently in. 

cat 		Display the contents of a whole file. 
cat myfile 	Show me all of the lines in "myfile", if myfile is longer 
		than 1 screen I will only see the last 20 lines or so. 

more 		Display the contents of a file page by page. 
more myfile 	Show me the first page of myfile. To see the next lines 
		touch space bar or the Enter key. To quit type q. 

head 		Display the first 10 lines of a file. 
head myfile 	Let me see the first 10 lines of myfile. 
[head -20 myfile] [Show me the first 20 lines of myfile] 

tail 		Display the last 10 lines of a file. 
tail myfile 	Show me the last 10 lines of myfile. 
[tail -20 myfile] [Like head, show 20 lines.] 

grep 		Find a string in a file or files. 
grep 'stuff' afile   Display all the lines in afile that contain the string 
		     "stuff", including lines that have words like stuffy or 
		     stuffing. Grep is a very powerful command. 

file 		Ask the system to guess what a file contains. 
file myfile 	The system will guess about the contents of a file. If it 
		tells you that the file is a binary, you shouldn't try to 
		display it. 

cd 		Change to a different directory 
cd mydir 	Change to the directory "mydir" which is a subdirectory of 
		the current directory. 
[cd ..] 	[change to the next higher directory in the tree. The ".." 
		notation is an abbreviation.] 

mkdir 		Create a new directory. 
mkdir mydir 	Create a directory called mydir from the current directory.

pwd 		Show me the directory I am currently working in. 
pwd 		Shows the current directory. Useful if you want to change 
		to a different directory. 

cal 		Display a calendar of the current month, or year. 
cal 		Display the current month. 
[cal 2002] 	[Output a calendar for the year 2002.] 

date 		Display the current system date and time. 
date 		Show me what day and time it is on the Unix machine I am 
		connected to. 

who 		Show me who is logged onto the system and where they are 
		logged in from. 
who 		Shows me the people currently logged onto the system. 
		Useful if I want to talk with them. Shows the login id, not 
		their real name. 

w 		Tell me who is logged on and what they are doing. 
w 		A more comprehensive display than who. Shows the login id, 
		as well as what they are doing and how long they have been 
		idle. 

finger 		Display information about one or more users. 
finger jl26 	Displays what the system knows about a user, in this case 
		jl26. Important because it gives the user's real name. 

talk 		Establish a 2-way connection between you and another user. 
talk jl26 	Sets up a two way, online chat session with the user. Both 
		users must be using a recognized terminal type. Exit with 
		^C. 

write 		Send a message to another user. 
write jl26 	Send a message to a user. In this case jl26. User, (jl26), 
		must be logged into the system for this to work. End 
		message with ^D. 

wall 		Send a message to everyone logged onto the system 
wall 		Send a message to everyone logged into the system. This 
		should only be used in extremes. 

mesg 		Disable, or enable talking or getting write messages. 
mesg n 		You can stop getting messages, and disable talk by turning 
[mesg y] 	off (n) messages. Use y to turn them back on. 

stty 		Set up terminal functions and values 
stty erase ^H 	This sets the ^H (backspace) key as the erase key. Use stty 
		with great caution, you can cause your terminal to stop 
		communicating. stty -a shows all the options. BE CAREFUL! 

man 		Invoke the online manual 
man man 	Display the online manual page for the "man" command. This 
		is a great tool to see what commands do, and how to use 
		them. 

wc 		Count the number of lines, words, and characters in a file. 
wc myfile 	Shows the number of lines, words, and characters, (in that 
		order), in myfile. 

exit 		Leave the Unix machine. 
exit 		This will log you off.