Is it possible to re-use Unix tools?

Question

Hi I have done some programming in C on Linux, lately I had some ideas for Mac apps and now I had some questions...
I suppose I'll had to learn Obj-C and Cocoa as that's the standard tool for programming on Mac? Now, what about Unix tools it came with, can I reuse it to some degree? I believe some GUI Tools that OS X came with reuses stuff from Darwin... like how Disk Utility uses diskutil...
So I am wondering, if I want to start programming, what should I learn first? As I said I am comfortable with C and coming from Linux background, I know a fair a bit about Unix, shell script, cron jobs, etc... but I like to know what's the way to make GUI Apps on OS X that possibly reuses functionality from Darwin Unix tools? Like, does Cocoa provides this functionality or?
And I do have set aside some money to invest in a Cocoa book or something.
Thanks.
Message was edited by: Sunnnz
Message was edited by: Sunnnz

Answer 1

Sunnnz,
One option is to use standard C calls to execute other command line tools, such as system(), fork()/exec(), popen()/pclose().
But if your intent is to build full fledged GUI applications then you probably will need to learn some of the other APIs and frameworks. Cocoa gives you NSTask that wraps much of the complexity of executing other tools into an Objective-C class.
AppleScript (using Script Editor) provides a "do shell script" command that can be used to execute shell scripts or command line tools from within your AppleScripts. However, plain vanilla AppleScript doesn't give you very much versatility for creating a GUI interface for your application.
But, you can also use AppleScript Studio (within Xcode). AS Studio merges AppleScript with Cocoa interface components and allows you to easily create fairly complex GUI applications that wrap calls to command line tools (using "do shell script").
One drawback of using "do shell script" within AppleScript or AS Studio is that you can't create an interactive session with the tool you launch. In other words, "do shell script" expects the tool it runs to run to completion before the "do shell script" call returns control to your AppleScript. In many cases this is not a problem since you can pass the tool or shell script all the command line options it needs and then get the result of the execution back into an AppleScript variable. But if your app truly needs to interact with the other process while it's running then you'll have to use something like Cocoa's NSTask or the lower level C functions mentioned above.
Steve