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CLI-CHEATSHEET.md

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Command Line Cheatsheet

Useful commands for Bash (Bourne-again shell), the default shell for most Linux distributions and macOS.

I don't remember anything!

Use the history command to list all the commands you previously typed:

$> history
24 ls
25 cd foo
26 ssh jdoe@archidep.ch
27 cat file.txt

Note that each command is prefixed by a number. Type an exclamation mark followed by that number to retrieve the command:

$> !26
$> ssh jdoe@archidep.ch

If you're looking for a specific command, you can filter your command history by piping it into the grep command. For example, this will search for all commands containing the word "ssh" in your history:

$> history | grep ssh
19 ssh-keygen --help
20 ssh-keygen
26 ssh jdoe@archidep.ch

Getting help (man, --help)

  • man ls displays the manual of the ls command on Unix systems.
  • help ls displays the help of the ls command in Git Bash on Windows.
  • git --help displays the help of the git command. Many (but not all) commands provide a help page.

Navigating

Where am I? (pwd)

Use the pwd command, meaning print working directory:

$> pwd
/Users/jdoe/Downloads

What is there? (ls)

Use the ls command, meaning list:

Command Effect
ls List the files in the current directory (invisible files are hidden)
ls -a List all files in the current directory, including invisible ones
ls -ahl List all files in the current directory, also displaying their mode, owner, group, size and last modification date
ls foo List all files in the foo directory inside the current directory

Move around (cd)

Use the cd command, meaning change directory:

Command Effect
cd . Move into the current directory (wheeeeee)
cd foo Move into the foo directory inside the current directory
cd ./foo Same as previous
cd foo/bar Move into the bar directory inside the foo directory inside the current directory
cd ./foo/bar Same as previous
cd .. Move into the parent directory (e.g. into /foo if you are in /foo/bar)
cd ../.. Move into the parent directory of the parent directory (e.g. into / if you are in /foo/bar)
cd ~ Move into your home directory
cd Same as previous
cd / Move to the root of the file system

Special paths (., .., ~)

Path Where
. The current directory (the same as indicated by pwd)
.. The parent directory (e.g. /foo if you are in /foo/bar)
~ Your user's home directory (e.g. /Users/username in macOS)
/ The file system's root directory on Unix systems

Reading

What's in this file? (cat, head, tail, less)

Display the entire contents of a file in the CLI with the cat command (as in concatenate):

$> cat file.txt
Hello
World

Display the first or last N lines (10 by default) of a file with the head and tail commands, respectively:

$> head file.txt

$> head -n 100 file.txt

$> tail file.txt

$> tail -n 50 file.txt

Display a large file in interactive mode, allowing you to scroll with the up and down arrow keys (exit this mode by typing the letter q, as in quit):

$> less file.txt

Writing

Create a directory (mkdir)

mkdir stands for make directory.

Create one directory in the current directory:

$> mkdir foo

Create a directory and all missing intermediate directories:

$> mkdir -p foo/bar/baz/qux

Create a file (echo, touch)

Create an empty file:

$> touch file.txt

Create (or overwrite) a file containing one line:

$> echo "Hello World!" > file.txt

Do the same with the tee command if you need to create a file with administrative privileges:

$> echo "Hello World!" | sudo tee file.txt

Append one line at the end of a file (also creates the file if it does not exist):

$> echo "Hello World!" >> file.txt

Again with the tee command if you need to create a file with administrative privileges:

$> echo "Hello World!" | sudo tee -a file.txt

Edit a file (nano)

Edit a file with nano:

$> nano /path/to/file.txt

Nano will always display available commands at the bottom of the screen. Ctrl-X is the one you will use most often, which saves and exits. Note that nano will ask you to confirm the file name. Just press Enter (unless you want to save your changes to another file, to keep the original one).

If you need superuser privileges to access the file, you can use sudo:

$> sudo nano /path/to/file.txt

Copy stuff (cp)

Copy a file to another location:

$> cp oldname.txt newname.txt

$> cp foo/oldname.txt bar/baz/newname.txt

Recursively copy a directory and all its contents:

cp -R olddirectory newdirectory

Move stuff (mv)

Move a file (or directory):

$> mv file.txt /somewhere/else

$> mv directory /somewhere/else

Delete stuff (rm)

Delete (or remove) a file:

$> rm file.txt

You can also delete a directory with rm by adding the -r (recursive) option.

Be EXTREMELY careful when you type this command. One wrong move and you could permanently lose a lot of files (e.g. if you misspell the name of the directory you want to delete).

$> rm -r directory

Finding stuff

Find files (find)

Recursively list all files in the current directory:

$> find .

Recursively list all JavaScript files in the current directory:

$> find . -name "*.js"

Find lines in files (grep)

Recursively find all files in the current directory containing the word "foo":

$> grep -R foo .

Environment variables

Display an environment variable:

$> echo $FOO
$> echo $PATH

Set an environment variable (it will be gone when you close the CLI):

$> export FOO=bar
$> echo $FOO

To be able to keep this environment variable in all future CLIs, save the export FOO=bar line to your ~/.bash_profile file (create it if it doesn't exist).

$PATH

$PATH is an environment variable that contains a semicolon-delimited (:) list of directories. When you type a command such as git, Bash will look for a binary file named git in each of these directories one by one and execute the first one it finds.

If it doesn't find such an executable, it will return a command not found error.

$> echo $PATH
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

You can modify your path by adding export statements to your ~/.bash_profile file (create it if it doesn't exist):

# Add the /foo directory to the beginning of $PATH
export PATH="/foo:$PATH"

# Add the /opt/local/bin directory to the beginning of $PATH
export PATH="/opt/local/bin:$PATH"

Do I have that command? (which)

Locate an executable in the $PATH with the which command:

$> which git
/usr/local/bin/git

$> which foo
foo not found