Opening Mac OS X Applications from the Command Line
The Terminal command to launch OS X gui apps is appropriately called ‘open’ and here is how it works at it’s most simple:
open -a ApplicationName
That will open the defined app named “ApplicationName”.
But open is much more powerful than that. If you just type ‘open’ at the command prompt, you’ll return the basic help file with details on how to properly use the command with a variety of flags and syntax. While the open command exists in all versions of Mac OS X, the abilities vary somewhat depending on what version of OS X the Mac is running. Nonetheless, in modern releases this is what you’ll see:
Usage: open [-e] [-t] [-f] [-W] [-R] [-n] [-g] [-h] [-b ] [-a ] [filenames] [--args arguments]
Help: Open opens files from a shell.
By default, opens each file using the default application for that file.
If the file is in the form of a URL, the file will be opened as a URL.
-a Opens with the specified application.
-b Opens with the specified application bundle identifier.
-e Opens with TextEdit.
-t Opens with default text editor.
-f Reads input from standard input and opens with TextEdit.
-F --fresh Launches the app fresh, that is, without restoring windows. Saved persistent state is lost, excluding Untitled documents.
-R, --reveal Selects in the Finder instead of opening.
-W, --wait-apps Blocks until the used applications are closed (even if they were already running).
--args All remaining arguments are passed in argv to the application's main() function instead of opened.
-n, --new Open a new instance of the application even if one is already running.
-j, --hide Launches the app hidden.
-g, --background Does not bring the application to the foreground.
-h, --header Searches header file locations for headers matching the given filenames, and opens them.
In other words, example simple command syntax could look like the following, opening “ApplicationName” with the file located at the path ‘/file/to/open':
open -a ApplicationName /file/to/open
You’ll note you don’t need the full path to the application name, but you would need the full path to a file name.
The usage is likely self explanatory to those who have experience in the command line environment, but for those who are new to the Terminal, don’t be too confused, it is easy to use and we’ll explain. For example, if you want to edit /etc/motd with TextWrangler to change your Message of the Day, but you hate the command line editors nano and vi, here is what you’d
$ open -a TextWrangler /etc/motd
Now you can edit these files in the familiar GUI. open is smart enough to know that when you apply the -a flag, you are launching an application so you don’t need to type in its full path. Obviously, it’ll still need the full path to the file you’re editing though.
There are many other usages for the open command rather than just editing text files, so use your imagination and get creative. open could be particularly useful to system administrators who utilize it in a shell script, perhaps to launch a specific GUI application at a scheduled time.
Also worth noting is that if you are launching an application with spaces in its name, you’ll want to add a backslash after each word, opening Adobe Photoshop CS would look like this:
$ open -a Adobe\ Photoshop\ CS
Launching GUI Apps as root from the Command Line
You can even open files with sudo by using the open command if you need to edit a file as root, for example:
sudo open -a TextEdit /tmp/magicfile
This will launch the target file into the desired application as root user, giving full root privileges to edit and modify the file, which is quite helpful for editing many system files. Of course, don’t modify any system file if you don’t know what you’re doing.
Creating Shell Aliases for Frequently Launched GUI Apps
So it’s kind of a pain in the butt to type a full command repeatedly, or to type out all that out over and over again, right? Well let’s make it easier by assigning an alias to an application that gets frequently launched. We’ll take the aforementioned Adobe Photoshop app as an example since the file name is lengthy, so here’s how we’ll do this with the Mac OS X default Bash shell:
First launch the profile or .bash_profile into a text editor:
$ nano .profile
$ open -e .profile
Ignoring whatever else may be in this file (it could be empty also), add the following to a new line:
alias photoshop="open -a Adobe\ Photoshop\ CS"
This creates an alias, so that the “open -a Adobe\ Photoshop CS” command is now shortened to simply ‘photoshop’. Save .profile, and you’re on your way! You can use the alias command in conjunction with open for virtually anything, just be sure to pick an alias to a command that doesn’t already exist.
The open command is really handy as you can see, if you have any other great uses for it in OS X, be sure to let us know in the comments.