pipe.swift

import Foundation
                                                                                                                                  
public enum ExecutionError: Error {                                                                                               
    case SomethingHappened                                                                                                        
}                                                                                                                                 
                                                                                                                                  
func execute(command: String, args: [String]? = nil, input: String? = nil) throws -> String {
     
    let task = Process()
    var inpipe: Pipe?
    
    task.launchPath = command

    if args != nil {
        task.arguments = args
    }
     
    if input != nil {
        inpipe = Pipe()
        task.standardInput = inpipe
    }
     
    let outpipe = Pipe()
    task.standardOutput = outpipe

    task.launch()

    if let inpipe = inpipe,
       let input = input {
           let bytes: [UInt8] = Array(input.utf8)
           let fh = inpipe.fileHandleForWriting
           fh.write(Data(bytes: bytes))
           fh.closeFile()
    }
     
    let output = outpipe.fileHandleForReading.readDataToEndOfFile().base64EncodedString()
    return output
}

// NOTE: this does not return what you'd expect. The returned string is Base64-encoded data
// (because that's what I needed for a particular use case).

// So if you want to do something "normal", e.g.
//
//       let result = execute(command: "/bin/ls", args: ["-a", "-l"])                                                              
//
// You'll then need to decode result as follows:
// 
//       let listing = String(data: Data(base64Encoded: res!)!, encoding: .utf8)!
//
// Needs some improvements. In particular, launch throws an error if the launchPath does                                           
// not point to a valid executable. Do we want to catch it and try and do something                                               
// like search a path?