You need to be aware that different from other scripting or programming languages, shell scripting heavily relies on the command-line applications provided to you by the OS. This means, since OS X is a BSD, that much of the things that work on Linux, will work slightly different on your computer, rendering a lot of tutorials useless. In general, you can expect your command line tools to have fewer features and flexibility than the Linux counterparts, although there are exceptions.
if you're unfamiliar with the shell and don't feel an overwhelming need to learn it, you might be better off using your favorite web scripting language (PHP, Ruby, Python) from the command line. The advantage there is the probably more consistent API across the entire library of functions.
bash itself, learn
- Conditions (including use of
] for defensive programming when handling files)
- Variable assignment
- Input and output redirection and piping
- Calling programs and shell functions (including how to capture their output and read their return values), both regular calls and with command substitution.
- Options. I love
set -u and refuse to work with scripts that cannot handle this.
- Variable types, arrays, globbing
The problem here is that
bash is very tied into the system with things like job control, and, for creation of complex scripts, has a rather steep learning curve.
In my experience *no section of the
bash man page is unnecessary. Do it long enough and everything in there is applicable somehow (and if it's just to answer questions on SU).
Some (in my experience) commonly used programs in shell scripts:
- File handling and navigation:
- Program execution:
- Data transformation:
Specific to OS X are probably the following:
growlnotify (if you have Growl)
And of course, depending on the exact nature of what you want to do, there are others...
date (BSD variant — very different from GNU),
netcat require you to install third party packages e.g. using Homebrew, MacPorts, or Fink.
If your scripts heavily use these command line programs, or can be written in such a way,
bash scripts are a good way to automate this.
Since you're on OS X, also look into AppleScript (via AppleScript Editor) and Automator. Both of these can be combined with shell scripts to achieve quite nicely integrated script solutions. If you're looking into controlling other OS X applications (e.g. your web browser), these are indispensable. While you can open URLs in different browsers using
open on the command line, retrieving data e.g. from loaded tabs requires Automator or AppleScript.
Also, other scripting languages such as
python are also pre-installed on your Mac and can be used to easily create simple helper utilities. These are more of a replacement of
bash and regular UNIX utilities. It depends on the nature of what you want to do.
If you want to move a handful of files around your disk, zip them up and transfer them via SSH,
bash is probably the best choice. As soon as you have real programming logic (anything involving a lot of objects or numbers), you should probably look into other scripting languages.