The Command Line Interface (CLI) is the fundamental method of interacting with Linux/Unix/OS X systems. When Linux and Unix were first developed, the CLI was the only way of communicating with the system.

Today, with the many Graphical User Interfaces ( GUIs) available, fewer users are now being exposed to what can be done from the command line. In particular, users of OS X systems are commonly ignorant of what can be done through their terminal.

The intent of this page and the posts that it references are to introduce the new Linux user and the OS X user to what can be done through the CLI.

What are CLI Commands

Commands that are entered at the command line are simply programs that have been developed over the years and are now part of the Unix/Linux/OS X distribution that you are using. There are hundreds of commands, some you will use often, others you may never use. You may also find the free PDF “Unix for the Beginning Mage” valuable.

Common Commands


Command OS X Linux Description
apropos * * search command descriptions for keyword
bzip2 * * file compression/decompression with the Burrows-Wheeler block sorting text compression algorithm and Huffman coding
cat * * concatenate and print file
chsh * * change user shell
chgrp * * change group ownership
cd * * change directory
dd * * convert and copy files
find * * Search for files or directories
file * * determine file type
history * * display the commands entered at the command line
ln * * make link
look * * List all lines of sorted text file that begin with specified word
ls * * list directory contents
man * * format and display the on-line manual pages
netstat * * print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
pwd * * print working directory
rsync * * file synchronization
sed * * stream editor
sudo * * execute a command as another user
tcpdump * * capture and analyze network traffic
time * * time a commands execution
top * * watch process related details such as CPU and memory usage
whatis * * Short description of command
zcat * * View compressed file

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