Frequently Used Unix Commands

Overview

The Unix operating system supports many commands. To review a more complete definition of any of the commands listed below, type man command at the Unix shell prompt (%), where you have replaced command with the name of a Unix command. For example, type man exit to find out more about the exit command.

Note This document assumes you are using Unix on the ITS Login Service (host name login.itd.umich.edu). These instructions apply to many other Unix machines; however, you may notice different behavior if you are not using the ITS Login Service.

Tip The variable files refers to a list of any number of files separated by white space; in the same way; names refers to a list of file or directory names separated by white space.

General

apropos command
Locates commands by keyword lookup.
exit
Terminates your current session, or shell.
man command
Displays the Unix manual page describing a given Unix command.

File System Navigation

cd
Returns to your home directory.
cd directory
Changes directory to make directory your current directory.
file files
Determines file type.
ls
Lists the contents of the current directory.
ls names
Lists the contents of the directories; names can name files and/or directories:
ls -l
. . . in a long format, showing permissions, owner, size, and other file info.
ls -a
. . . all files, including "hidden" files (file names that begin with a dot ".").
ls -R
. . . Recursively, for all subdirectories.
ls -t
. . . in time order (when modified, newest to oldest) rather than in name order.
pwd
Displays the name of the current directory, or "print working directory."

File/Directory Manipulation

compress files
Reduces the size of a file.
uncompress files
Restores compressed files to their original form.
cp file1 file2
Copies file(s).
cp files directory
Copies file(s) into a directory.
cp -r dir1 dir2
Copies a directory and, recursively, its subdirectories.
mkdir directory
Creates, or "make" a directory.
mv file1 file2
Moves a file or, if file1 and file2 are in the same directory, rename a file.
mv files directory
Moves files into a directory.
mv dir1 dir2
If directory dir2 exists, moves dir1 into dir2; otherwise, rename dir1 as dir2.
rm files
Removes (erase) file(s).
rm -r names
Removes files, directories, and recursively, any subdirectories.
rmdir directory
Removes directory (directory must be empty).

Data Manipulation

cat files
Concatenates file(s); you can use cat to display the contents of a file (this is not advisable if the file is a binary file).
grep "pattern" files
Displays all lines in the files that match a pattern.
more files
Displays contents of files one screen at a time.
sort files
Orders the lines in a file or files alphabetically (this command does not alter the file or files -- it merely displays the sorted output to the screen):
sort -r files
. . . in reverse order.
sort -n files
. . . numerically (puts 2 before 10 instead of after).

Networking/Communications

ssh hostname
Connects to a remote host using Secure Shell.

Miscellaneous

!!
Repeats last shell command.
!string
Repeats last shell command that began with string (for example, type "!m" to repeat the last command that began with "m").
cal
Displays a calendar of the current month.
cal month year
Displays a calendar of the given month and year. Note that the year must be fully qualified, for example, "2003" and not "03."
clear
Clears terminal screen.
date
Displays the current local date and time.
who
Displays a list of users currently logged in.
Tags: 
Last Updated: 
Thursday, March 20, 2014