As our team move to Mac OS X development environments and Git version control I wanted to prepare a post covering some Command Line essentials. As a developer working with these technologies you don’t have to use the command line but you’ll probably want to - at least some of the time. This post is intended to be something of a beginners reference.

In preparing this post I’ve used a few sources including:

Here’s a summary of the essentials that will probably be most useful.

Basics of the Command Line

The command line is simply an different way of interacting with the operating system or running programs. You type commands at a prompt instead of using a GUI. This can be off-putting initially, but a little bit of learning can save you a lot of time. For example, I can empty the contents of my Downloads directory in Mac OS X by either:

  • Clicking on Finder in the dock, clicking on ‘Downloads’ in the favourites, selecting all the documents shown and selecting ‘Move to trash’ from the context menu, or;
  • Typing cd ~/Downloads; rm * in Terminal (the command line application provided on Mac OS X)

Admittedly, the second option seems a bit cryptic but it quickly becomes second nature as you start to use the command line. Let’s unpick this example. We have two independent commands separated by a semi-colon. The first command ‘cd’ navigates to or ‘changes directory’ to to Downloads in our home directory. The second command, ‘rm’ removes everything (denoted by ’*’) in the current directory.

Essential commands

Here are a few essential commands which I suggest beginners have a play around with.

Moving around

  • pwd (print working directory) shows your current location in the file system.
  • Use cd (change directory) to move around the file system (cd ~ takes you back to the home directory, cd - lets you toggle to your last directory).
  • ls will list what’s in the current directory

Using history {#history}

You can view all of your previous commands by typing history. When you do this, you’ll see a number next to each command. By typing that number preceded by ’!’ you’ll be able to run that command instantly. The history can get pretty long, so it is really helpful to search for a specific command. I often find myself doing this for long Git commands (such as git log --oneline --decorate --graph). To do this I’d type history | grep log which is essentially ‘piping’ the output of history through another command (grep to an amazingly powerful search utility) which searches for a specific pattern, in this case ‘log’.

History shortcuts

  • !str lets you find the last command that began with str.** **For example, !v will find and run the last command that began with the letter v
  • !?str lets you find the last command the contains str
  • !$ gives you access to your last argument. For example, if the last command you typed was cd ~/Downloads and you followed that with !$ you would be presented with ~/Downloads

Update to even better history with ‘reverse-i-search’ {#update}

I’ve just today been introduced to a really handy command line feature called reverse-i-search. What this does is allow you to search your history and traverse the results. Simply type Ctrl + R within a terminal window to bring up the search, enter your keyword and then repeat Ctrl + R to traverse the matches.

Creating, moving and deleting files

  • touch, as well as creating files, will update the access time for an existing file.
  • cp lets you copy the contents of one file to another.
  • mv can be used to move files around

Searching with find

The find command recursively searches directories, looking at every file until it finds a match. For example, I can find all the files anywhere in my home directory with names that contain the string ‘index’ with:

find ~ -name "*index*"

Fun utilities

There are many useful utilities available on the command line, here are a couple of the more ‘fun’ ones (use the man command to find out more about them)

  • the expr command provides a simple calculator
  • units provides a simple way to convert units of temperature, length, area etc.

Mac only commands

Everything mentioned so far should work across *nix command line applications, each of which have their own special features. Here are a few of the many that are specific to Macs.

Open

The open command is a pretty flexible way of opening things. Here are a few examples:

  • open -a PhpStorm will open PhpStorm. You can do this for any application within your Applications directory
  • open http://www.google.com will open the web page in your default web browser
  • open -a "Google Chrome" http://localhost:8000 passing the -a argument lets you specify the application (browser) to use
  • You can also pipe the output from Unix commands to open. For example, ls -a | open -f will show the contents of the current directory in your default text editor

Screen capture

The screencapture command allows you to create and save a screen capture to a filename of your choice. For example screencapture > sc.png

Text to speech

the say command lets you use Mac OS X text to speech capability. For example:

  • type say "I am talking" and text to speech will say “I am talking”
  • say -f ramblings.txt -o audio_file.aiff will create an audio file (in aiff format) of the text within the ramblings.txt file

General tips

  • Every command has a manual page accessed by typing man followed by the command name (i.e. man pwd)
  • Because the Terminal can show both the commands you’ve typed and their output, the screen can get a bit cluttered. At any point you can use the clear command to hide the scrollback (your previous commands and their output) or cmd + k to clear the scroll back.
  • All commands follow a specific structure: command optionally followed by options optionally followed by arguments. i.e. ls -a Pictures
  • You can separate commands with a semi-colon

Bringing it all together

Here’s a little something which, using the techniques shown above (and one other called xargs, which is probably a bit too much to go into at this point) can save you time every time you sit down to start working. By typing

echo 'PhpStorm.app MAMP\ PRO.app' | xargs -t -n1 open -a

You’ll instantly open SourceTree, PhpStorm and Mamp Pro. Yes, that’s a lot to type but you can very easily save an alias for that command as, say, devgo which would allow you to open all your development software.

I really hope this post will be useful to others and would be very happy to clarify or help with any of the commands/techniques mentioned.