Vincent Gable

The best way to call a shell-command from Coca is by using an NSTask. Here are the three resources on using an NSTask that I found the most helpful:
CocoDev’s write up
A few quick exaples
NSTask Class Refrence

And here is some sample code to do it for you. You are free to use this code however you please, but attribution is always appreciated. The two principle functions are:

+ (NSString*) executeShellCommandSynchronously:(NSString*)command executes the command “command” with sh, wait until it finishes, and return whatever it printed to stdout and stderr as an NSString.
CAUTION: may deadlock under some circumstances if the output gets so big it fills the pipe. See http://dev.notoptimal.net/search/label/NSTask for an overview of the problem, and a solution. I have not experienced the problem myself, so I can’t comment.

executeShellCommandAsynchronously: will have sh execute command in the background, without blocking anything.

For quick hacks, the POSIX int system(const char* command) function, might be a good one-line solution. It synchronously evaluates command with sh.

Enjoy!