Basic Unix Commands

Command	Description*	Example command(s)**
apropos	Locate commands by a keyword	apropos delete
cd	Change directory “cd [directory_name]” change to named directory within current directory “cd” change to your home directory “cd ..” change to directory above	cd Data
cp	Copy a file (see also “scp”) option “-p” keeps same date and time	cp -p file2.dat lowerdirectory/
find	Find a file in the current directory and those below it	find . -name “filename.ext” -print
grep	Search for text within the designated files	grep “look for this string” *
kill PID	Terminate a process, must give process identification number (PID).	kill 12068
man	Manual (help) on a particular command, shows options available	man apropos
more	Print a text file to the screen	more file2.dat
mv	Rename (move) a file	mv file2.dat file3.dat
ls	List file directory “-a” lists all files, including those that begin with “.” (i.e. “hidden” files) “-l” lists in long format “-la” lists all files in long format “-s” lists files and their sizes	ls filename ls -a filename ls -la filename
lp	Print a file	lp file3.dat
mkdir	Make (create) a subdirectory	mkdir directory2
ps	Report process status	ps
pwd	Print working (current) directory	pwd
rm	Remove (delete) a file	rm file3.dat
rmdir	Remove (delete) a directory	rm directory2
scp	Secure copy (between two computers). You will be prompted to give your password to the other machine. You can copy from or to another computer (machine2). Username (and “@”) is not necessary if it is the same as the username on the first (current) machine.	To machine2: scp -p file4.dat username@machine2:Directory_Path/ From machine2: scp -p username@machine2:Directory_Path/file4.dat./
tail	Prints out the last portion (one screen) of a file	tail file3.dat
top	See a table of continuously updated data on currently running processes	“top” enter “q” to exit
wc	Word count: counts words (-w), lines (-l), characters (-m), or bytes (-c).	wc -l filename
whatis	Tells what a command is	whatis mkdir
who	Who is on the system	who
whoami	Who you are (on the system)	“whoami” or “who am i”
which	Locates program executable files defined by an alias, need to give alias name	which mkdir

*Options are listed after the initial command with a preceeding space and hyphen (e.g. wc -w filename). One letter options may be listed separately (each with a preceeding space and hyphen, e.g. ls -l -a filename) or together after a single space and hyphen (e.g. ls -la filename). The option must be designated after the command but before the file(s) “receiving” the action.
**Where “filename” is given here, directory names, wild card (“*”), or multiple filenames may be used where appropriate. A file not in the current directory should be preceeded by the path name, which can be relative to the current directory (e.g. ../directory/filename) or full path (e.g. /home/username/directory1/directory2/filename).

Other Help

File-Access Permissions

If you execute the command “ls -l” or “ls -la”, the first column is a block of 10 characters that shows permissions for the file or directory listed. For example,

drwxr-xr-x
-rw——-
-rw-r–r–
The first character indicates if the entry is a directory (d), link (l), or normal file (-).
The next nine characters show permissions to read (r), write (w), and execute (x) the file or directory. A “-” indicates no permission for one of those three actions. Characters 2-4 show the user’s permissions, 5-7 the group’s permissions, and 8-10 the other user’s (the world’s) permissions. To change the permissions use the command “chmod”. Usually directories are drwxr-xr-x. Files are usually -rwxr-xr-x if the file is an executable file or a script and -rw-r–r– if a non-executable file (e.g. data or text). A few sample commands are listed below (the command affects the file or directory named).

Commands that give the most common file permissions:

chmod 644 name Allow user to read and write. Allow group and others to read.
chmod 755 name Allow user to read, write, and execute. Allow group and others to read and execute.
chmod +x name Give user, group, and others permission to execute as well as previous permissions.

Commands for less common file permissions:

chmod 777 name Allow user, group, and other users to read, write, and execute.
chmod 0400 name Allow only the user to read.
chmod 0600 name Allow only the user to read and write.
chmod 0700 name Allow only the user to read, write, and execute.
chmod 0007 name Allow only other users (the world) to read, write, and execute.
chmod o=r name Give other users (the world) permission to read.
chmod o+x name Also give other users (the world) permission to execute.
chmod o-x name Take execution privileges away from other users (the world).
chmod u=rwx name Give user permission to read, write, and execute.
chmod g-rwx name Take away group’s permissions to read, write, and execute.

Enter “man chmod” for more detailed information.

Stop a Running Program

Crtl-C, kills a running process in the current window (may not work within programs that have their own interface within a terminal or shell window, e.g. text editors).
Use kill as described in table above from another shell (or terminal).

Symbols

“./” Current directory–to run a program or script that is in the current directory enter “./name”.
“../” Directory above–you may use multiple “../”s to reach directories far above the current one (e.g. “../../../”). To reach a directory at the same level as your current directory–without leaving the current directory, use “../name2″.
“>” –place screen output in a text file, e.g. “wc -l filename > file2.txt” will count the number of lines in filename and write that information in file2.txt.
“<” –use information in subsequent file as input, e.g. program options < input.txt. This is useful for programs that require user input to be entered as the program runs.
“|” “Pipe” output from one program into another–the data becomes input to the second program. For example, the following command counts the number of files in the current directory: “ls * | wc -w”. In this case, a file name is not needed after “-w” because the output from “ls *” is the input.

Tar Files (For Archiving or Transferring)

tar -zcvf ../mytarfile.tar ./* takes all files in the current directory and writes a compressed (gzip) tar file in directory above
tar -cvf ../mytarfile.tar ./* takes all files in the current directory and writes a tar file in directory above
tar -zxvf mytarfile.tar unpacks (gunzip) a compressed tar file in the current directory
tar -xvf mytarfile.tar unpacks a tar file in the current directory

Text Editors

vi is a standard UNIX editor. The following are other text editors that may or may not be available on your machine: emacs, jot, nedit, pico, and xedit. These may open a new window and allow you to use a mouse, or they may operate within your current shell or terminal window.

Within a Program that Runs in a Shell or Terminal Window

“h” generally gives help
“q” generally exits

Compiled by D. Belnap, 14 May 2010, please email suggestions or corrections to David {dot} Belnap {at} utah {dot} edu.
Disclaimer: This webpage is meant to show commonly used UNIX commands. It is not meant to be a comprehensive list..