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NEH Institute materials

July 2017

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Command line quick reference

Getting started

The shell is a window on your desktop where you type commands and then run them by pressing the Enter (or Return) key. Although it’s sometimes called “the Unix shell”, Windows, Mac, and Linux all come with command line interfaces that support many of the same commands:

When it’s your turn to type, the shell displays a prompt, which may look something like:

The text of the prompt is configurable, and by default it adapts to the machine and user, so yours will look different from ours, but unless you’ve specified otherwise, it will end with either a dollar sign ($) or a right angle bracket (>).



We provide brief summaries of the commands we use most often below, but for comprehensive reference, we recommend the operating-system-specific command-line references at

Directory and file names

Although applications, including the shell, will let you create filenames that are difficult to work with, for your own sanity:

Completion and recall

The shell can complete command and file names for you without requiring you to type them in full, and it can also rerun commands without retyping.

You can edit a command you’ve recalled from the history by moving back with the left-arrow key, and you can jump to the beginning or end with Ctrl-a and Ctrl-e. In MacOS you can depress the Option key and click in the recalled line to move the cursor there directly.


The asterisk means “zero or more characters” and the question mark means “exactly one character”. (These are confusingly similar to but different from their regex meanings.) E.g., ls *.txt lists all files in the current directory that end in “.txt”.

Shell commands by category

These lists are only brief reminders of the commands we use most often; they’ll help you find the command you need to perform a task, but they won’t tell you how it works. To get more information about a command, type man command-name (replacing “command-name” with the name of the command you are looking up). If your shell does not support man (Windows users), the contents of the man pages are easily found on line (e.g., at

Get oriented

Command Mnemonic What it does
cd change directory by itself takes you to your home directory,
otherwise specifies a destination
clear [none] clears the screen (or Ctrl+l)
pwd print working directory displays your current location in the filesystem
whoami [none] displays your userid

Explore your files

Command Mnemonic Example What it does
grep global regular expression print grep stuff * finds lines in files that contain “stuff”
less [none] less filename.txt pages through “filename.txt”;
use the space bar to page forward, type q to quit
ls list ls *.txt lists the files that match the pattern (or, with no argument, all files)

Manipulate your files

Command Mnemonic Example What it does
cp copy cp oldfile.txt newfile.txt copies “oldfile.txt” as “newfile.txt”
mv move mv oldfile.txt newfile.txt renames “oldfile.txt” as “newfile.txt”
mv move mv *.txt archive moves all text files into subdirectory called “archive”
rm remove rm unwanted-file.txt deletes “unwanted-file.txt”

There is no undelete, but you can retrieve the last committed version from GitHub.

Manipulate your directories

Command Mnemonic Example What it does
mkdir make directory mkdir new-directory creates a directory called “new-directory”
rmdir remove directory rmdir unwanted-directory deletes the directory called “new-directory”

Edit your files

Text editors commonly invoked from the command line include nano, vim, and emacs. nano is the easiest for new users (it displays prompts for common commands); most experienced users prefer the other two. To edit a file called “filename.txt” with vim, type vim filename.txt.

Create and unpack zip archive files

Sets of files are often distributed as a single zip archive file.

Command Example What it does
zip zip *.txt creates “” and includes all text files in it
unzip unzip disgorges all files in “”

Redirection and piping

In the table below, grep stuff * displays all lines that contain the string “stuff” in all files in the directory. wc -l displays the number of lines in a file.

Symbol What it means Example What it does
< take input from file wc -l < filename.txt displays the number of lines in “filename.txt”. Note that the output is different from wc -l filename.txt.
> write output to file grep stuff * > outfile.txt saves the results to “outfile.txt” instead of displaying it on the screen
2> write errors and warnings elsewhere grep stuff * 2> /dev/null suppress error messages and warnings, which might otherwise clutter your screen
| the output of the first command is the input to the second history | grep stuff outputs the command history not directly to the screen, but into a filter to display only commands that include the string “stuff”