Example of piping together commands in swift.

PipeExample.swift

#!/usr/bin/swift
import Foundation
 
let catProcess = Process()
catProcess.executableURL = URL(fileURLWithPath: "/bin/cat")
catProcess.arguments = ["PipeExample.swift"]

let pipe1 = Pipe()

let grepProcess = Process()
grepProcess.executableURL = URL(fileURLWithPath: "/usr/bin/grep")
grepProcess.arguments = ["-n", "pipe2"]

catProcess.standardOutput = pipe1
grepProcess.standardInput = pipe1

let pipe2 = Pipe()
grepProcess.standardOutput = pipe2

pipe2.fileHandleForReading.readabilityHandler = { fileHandle in
    let data = fileHandle.availableData
    if data.isEmpty { // EOF
        pipe2.fileHandleForReading.readabilityHandler = nil
        return
    }
    print(String(data: data, encoding: .utf8)!)
}

try catProcess.run()
try grepProcess.run()
grepProcess.waitUntilExit()