Transcribed from Tower’s blog post
$ pwd
Display path of current working directory
$ cd <directory>
Change directory to <directory>
$ cd ..
Navigate to parent directory
$ cd -
Navigate to previous directory
$ ls
List directory contents
$ ll
List detailed directory contents
$ la
List detailed directory contents, including hidden files
$ mkdir <directory>
Create new directory named <directory>
$ cat <file>
Output the contents of <file>
$ less <file>
Output the contents of <file> using the less command (which supports pagination etc.)
$ head <file>
Output the first 10 lines of <file>
$ <cmd> > <file>
Direct the output of <cmd> into <file>
$ <cmd> >> <file>
Append the output of <cmd> to <file>
$ <cmd1> | <cmd2>
Direct the output of <cmd1> to <cmd2>
$ clear
Clear the command line window
$ rm <file>
Delete <file>
$ rm -r <directory>
Delete <directory>
$ rm -f <file>
Force-delete <file> (add -r to force-delete a directory)
$ mv <file-old> <file-new>
Rename <file-old> to <file-new>
$ mv <file> <directory>
Move <file> to <directory> (possibly overwriting an existing file)
$ cp <file> <directory>
Copy <file> to <directory> (possibly overwriting an existing file)
$ cp -r <directory1> <directory2>
Copy <directory1> and its contents to <directory2> (possibly overwriting files in an existing directory)
$ touch <file>
Update file access & modification time (and create <file> if it doesn’t exist)
$ chmod 755 <file>
Change permissions of <file> to 755
$ chmod -R 600 <directory>
Change permissions of <directory> (and its contents) to 600
$ chown <user>:<group> <file>
Change ownership of <file> to <user> and <group> (add -R to include a directory’s contents)
$ find <dir> -name "<file>"
Find all files named <file> inside <dir> (use wildcards * to search for parts of filenames, e.g. "file.*")
$ grep "<text>" <file>
Output all occurrences of <text> inside <file> (add -i for case-insensitivity)
$ grep -rl "<text>" <dir>
Search for all files containing <text> inside <dir>
$ ping <host>
Ping <host> and display status
$ whois <domain>
Output whois information for <domain>
$ curl -O <url/to/file>
Download <file> (via HTTP[S] or FTP)
$ ssh <username>@<host>
Establish an SSH connection to <host> with user <username>
$ scp <file> <user>@<host>:/remote/path
Copy <file> to a remote <host>
$ ps ax
Output currently running processes
$ top
Display live information about currently running processes
$ kill <pid>
Quit process with ID <pid>
$ ssh-keygen -t rsa -C athletics
Creates a new ssh key, using "athletics" as a label.
You will be prompted for a filename. It is recommended that you use <project name>\_rsa as opposed to the default id_rsa.
$ pbcopy < ~/.ssh/<project name>_rsa.pub
Copies the contents of the <project name>_rsa.pub file to your clipboard.
On the command line, help is always at hand: you can either type man <command> or <command> --help to receive detailed documentation about the command in question.
On Unix systems, file permissions are set using three digits: the first one representing the permissions for the owning user, the second one for its group, and the third one for anyone else.
Add up the desired access rights for each digit as following:
4— access/read (r)2— modify/write (w)1— execute (x)
For example, 755 means “rwx” for owner and “rx” for both group and anyone. 740 represents “rwx” for owner, “r” for group and no rights for other users.
If you plan to run a series of commands after another, it might be useful to combine them instead of waiting for each command to finish before typing the next one. To do so, simply separate the commands with a semicolon ; on the same line.
Additionally, it is possble to execute a command only if its predecessor produces a certain result. Code placed after the && operator will only be run if the previous command completes successfully, while the opposite || operator only continues if the previous command fails. The following command will create the folder “videos” only if the cd command fails (and the folder therefore doesn’t exist):
$ cd ~/videos || mkdir ~/videos
Various keyboard shortcuts can assist you when entering text: Hitting CTRL+A moves the caret to the beginning and CTRL+E to the end of the line.
In a similar fashion, CTRL+K deletes all characters after, CTRL+W deletes a single word before the caret, and CTRL+U all characters in front of the caret.
Pressing CTRL+L clears the screen (similarly to the clear command). If you should ever want to abort a running command, CTRL+C will cancel it.
Whenever entering paths and file names, the TAB key comes in very handy. It autocompletes what you’ve written, reducing typos quite efficiently. E.g. when you want to switch to a different directory, you can either type every component of the path by hand:
$ cd ~/projects/acmedesign/docs/
...or use the TAB key (try this yourself):
$ cd ~/pr[TAB]ojects/ac[TAB]medesign/d[TAB]ocs/
In case your typed characters are ambiguous (because “ac” could point to the “acmedesign” or the “actionscript” folder), the command line won’t be able to autocomplete. In that case, you can hit TAB twice to view all possible matches and then type a few more characters.
The command line keeps a history of the most recent commands you executed. By pressing the ↑ key, you can step through the last called commands (starting with the most recent). ↓ will move forward in history towards the most recent call.
Bonus tip: Calling the history command prints a list of all recent commands.
File and directory paths can get long and awkward. If you’re addressing a path inside of your home folder though, you can make things easier by using the ~ character. So instead of writing cd /Users/your-username/projects/, a simple cd ~/projects/ will do.
And in case you should forget your user name, whoami will remind you.
The less command can display and paginate output. This means that it only displays one page full of content and then waits for your explicit instructions. You’ll know you have less in front of you if the last line of your screen either shows the file’s name or just a colon :.
Apart from the arrow keys, hitting SPACE will scroll one page forward, b will scroll one page backward, and q will quit the less program.
The output of a command does not necessarily have to be printed to the command line. Instead, you can decide to direct it to somewhere else.
Using the > operator, for example, output can be directed to a file. The following command will save the running processes to a text file in your home folder:
$ ps ax > ~/processes.txt
It is also possible to pass output to another command using the | (pipe) operator, which makes it very easy to create complex operations. E.g., this chain of commands will list the current directory’s contents, search the list for PDF files and display the results with the less command:
$ ls | grep ".pdf" | less