I love learning new commands and tools to optimize my workflow on my Mac. Since I have started working with more terminal-oriented applications, there are several commands that I use that I'd love to share with beginners and terminal lovers alike.

Note: This article assumes that you're using some type of UNIX shell, with a preference towards Mac. Some of these commands may not work on Windows CMD/Powershell.

Basic Commands

Commands in a shell can be used in a ton of different ways - but I'd say that the important ones to learn fall under three main categories:

1. Navigating and Working with Files & Directories
2. Manipulating Output for Input
3. Finding Things

Navigating and Working with Files & Directories

On a computer, files and directories (otherwise known as folders) are responsible for managing information. Here are some commands to make your life easier when working with files:

• cd - navigate to different directories
• pwd - see the name of the current directory
• ls - lists all files in the current directory
• mkdir - make a new directory
• touch - make a new file
• cp - copy a file
• mv - move a file or directory
• rm - removes a file or directory
• zip - compresses files into a zip archive
• unzip extracts files from a zip archive
• chmod - Allows you to make a file executable and change permissions granted to it by your machine.
  • In order to make a file executable, you can type chmod +x [name of file]
• tar - Allows you to work with tarballs in a Linux command line. It has a long list of uses, including package management for systems.
  • tar -cvf allows you to create a .tar archive
  • tar -xvf allows you to "untar" a .tar archive
  • tar -tvf list the contents of a .tar archive

Honorary Mention: sudo

sudo is a very widely used command in bash interfaces that allows you to run a command with administrative or root privileges.

For example, if you edit any files in the root directory (also known with the path /) of your machine without sudo privileges, you will be denied permissions to edit the file.

For your safety, there are a couple of things your computer will not allow you to do as a sudo'd command, i.e. running bash scripts.

Manipulating Output for Input

Often times when scripting the goal you are trying to achieve is to run filters through text, check output logs from a server, or run batch commands on multiple files.

Here are some commands that can be beneficial for manipulating file output:

• cat - show a file's contents
• head - displays the first few lines of a file
• tail - displays the last few lines of a file
  • Using the -f flag with tail will allow you to see updates to the file as they are coming in. This is extremely helpful for tracking log output from servers.
• | - The pipe character take a command's output and uses it for the input of another command
• * - matches zero or more characters in a filename
  • There is actually a whole way of matching multiple files and names via globs!
• ? - matches any single character in a filename
• > - stores a command's output to a file, and creates a new file if one doesn't already exist
  • WARNING: This will override and replace all contents that were in the original file.
• >> - concatenates a command's output to a file, creates a new file if none is found

Finding things

• echo - show text or the compiled text of other commands. Great for testing commands out.
• grep - allows you to find results line by line using some sort of pattern or regular expression.
• ack - similar to grep, but has a better code search because it knows to search in places you'd expect it to search. (ignores version control directories, etc.)

Other helpful commands I've found

• pbcopy - Copy selected text into your clipboard buffer

• pbpaste - Paste the selected text in the terminal from your clipboard manually

• history - Prints the command history for your session

  • This is really useful with grep and the pipe symbol, which will allow you to search through your history: history | grep [part of command]

• curl - Allows you to make HTTP calls RESTful endpoint

• kill - Kills a running process given a process id (pid)

• killall - Kills all running processes of a certain type

• lsof -i tcp:[port number here] - list all running processes on a specific port

  • This one is particularly useful for when you get an error like:

  Error: listen EADDRINUSE :::3005
      at Object.exports._errnoException (util.js:1023:11)
      at exports._exceptionWithHostPort (util.js:1046:20)
      at Server._listen2 (net.js:1261:14)
      at listen (net.js:1297:10)
      at Server.listen (net.js:1375:9)
      at Object.<anonymous> (/path/to/node/server/server.js:15:34)
      at Module._compile (module.js:571:32)
      at loader (/path/to/node/modules/node_modules/babel-register/lib/node.js:144:5)
      at Object.require.extensions.(anonymous function) [as .js] (/var/www/html/gcsbpo/rocc/node_modules/babel-register/lib/node.js:154:7)
      at Module.load (module.js:488:32)
  

  It provides an easy way to find out the pid to kill the running process.

Shortcuts/Tips & Tricks

• !! - repeats the last command executed
• !$ expands the final argument of the previous command. Useful for chaining commands on the same file
  • These are thanks to Thomas
  • ! [number]: Repeat command from your history (you can see the available command-history using fc -l (or fc -l 1 to see all the contents of your history)
  • !! [extra stuff]: Re-execute last command, tacking on [extra stuff] at the end of the command.
  • [extra stuff] !!: Re-execute last command, tacking on [extra stuff] at the beginning of the command. Very handy for executing something as a regular user that needs to be ran with sudo
  • !!:s/[SEARCH]/[REPLACE]: Re-execute last command, replacing first substring [SEARCH] with [REPLACE]
  • !!:s/[SEARCH]/[REPLACE]: Re-execute last command, replacing all substring [SEARCH]es with [REPLACE]es
• clear - clears all output from the terminal, old output - can still be accessed by scrolling up
• CMD + k - clears all output from the session, only previously called commands are retained
• CTRL + c - Aborts the current running process and closes it.
• CTRL + z - Pauses (SIGSTP) any the current running process
  • NOTE: CTRL + C aborts the process, but CTRL + z leaves it idling in memory.
• CTRL + a - Takes you to the beginning of the bash input
• CTRL + e - Takes you to the end of the bash input
• CTRL + u - Clears all input before the cursor
• CTRL + r - Opens a prompt that will search the previous commands from your session
• jq is a great tool for printing out JSON!

Conclusion

Learning how to navigate the terminal is definitely daunting at first, but after spending some time scripting you'll find that these commands can save you tons of time on a day to day tasks that you do.

Personally, I'm starting to reach the point where I navigate faster via Terminal than when I use Finder.

If you have any commands, shortcuts, or tips I should add to this post, please leave me a comment! Would love to add more.