ShellTask

Simple wrapper of NSTask that supports async execution and easy error and output handling.

Introduction

So I was writing a command line app in Swift and needed to execute a bunch of command line tasks from within. Turns out that getting the complete output from large commands was a little bit tricky and a lot of the stuff I found on the internet was either really outdated or just useless to me. Hence ShellTask. A simple class that wraps NSTask allowing you to easily create, launch and process the output of a command asynchronously.

Installation

Well at the moment, you just need to drag ShellTask.swift into your project and it should just work.
I haven't added Swift Package Manager, Cocoapod or Carthage support yet because I don't know how well this works in all scenarios so please let me know and we can look at other installation alternatives later.
Also only tested it on OS X using Xcode 7.2.1, I don't know if NSTask works on Linux using open source stuff.

Examples

Check out the ShellTaskExample project in the repo, its got most stuff covered.

Creating a basic task:

let task = ShellTask(launchPath: "/usr/bin/curl")
task.arguments = [ "https://api.github.com/" ]

This task is the equivalent to calling curl https://api.github.com/ from terminal.

Launching a task:

// launch the task
task.launch { result in
    
    // switch on our result,
    switch result {
    case .Success:
        print("task completed executed successfully.")
        
    case let .Failure(code):
        print("task terminated with code:", code)
    }
}

This will launch the task asynchronously and report back a ShellTask.Result enum value indicating the success of the task.

• .Success means that the NSTask returned a terminationStatus of EXIT_SUCCESS (0).
• .Failure(Int32) means that the terminationStatus was not EXIT_SUCCESS and the actual status is the supplied argument.

I/O Channel Options

By default, there are no ShellTask.IOOption values set on either outputOptions or errorOptions. This means that the ouput is not processed in any way. There are however some options available:

• .Print(prexix: String?) By setting this option, the task will print the output received on the file handle directly via the print() function in Swift. There is also an optional prefix parameter that will be added to each line of the output if supplied.
• Handle(callback: (availableData: NSData) -> Void) By setting this option, the task will callback to the supplied closure (callback) whenever there is data available. This is called directly from theNSFileHandleDataAvailableNotification notification allowing you to manually process the data yourself if you want.

You can use these options in conjunction with each other if you would like.

Printing with a Prefix:

task.outputOptions = [
    ShellTask.IOOption.Print(prefix: "[xcodebuild]")
]

Handling the output manually:

// somewhere to store the output as we recieve it.
let buffer = NSMutableData()

// add the handle option to our output. append the data we receive to our buffer.
task.outputOptions = [
    ShellTask.IOOption.Handle { availableData in
        buffer.appendData(availableData)
    }
]

// launch the task
task.launch { result in
    
    // at the time of this callback being executed, the output has finished so `buffer` is now complete with all the output data.
    print(buffer)
}

License

Do what you want with it.

Conclusion

Let me know if it doesn't work and I'll see if I can help. Enjoy