Example of creating a subprocess in Swift.

sub_process.swift

import Foundation

let process = Process()
process.executableURL = URL(fileURLWithPath:"/bin/bash")
process.arguments = ["-c", "ls"]

try? process.run()
let standardInputFH = process.standardInput as! FileHandle
let standardOutputFH = process.standardOutput as! FileHandle
let standardErrorFH = process.standardError as! FileHandle
print("PID: \(process.processIdentifier)")
print("stdin FD: \(standardInputFH.fileDescriptor)")
print("stdout FD: \(standardOutputFH.fileDescriptor)")
print("stderr FD: \(standardErrorFH.fileDescriptor)")