SwiftでCommand Line Toolを叩く時はProcessを使いますが，grepしたい時どうすればいいのかわかりづらかったので備忘録

func extractDefaultInternet() {
    // $ netstat -rnf inet | grep default
    let pipe1 = Pipe()
    let pipe2 = Pipe()

    let netstat = Process()
    netstat.launchPath = "/usr/bin/env"
    netstat.arguments = ["netstat", "-rnf", "inet"]
    netstat.standardOutput = pipe1

    let grep = Process()
    grep.launchPath = "/usr/bin/grep"
    grep.arguments = ["default"]
    grep.standardInput = pipe1
    grep.standardOutput = pipe2

    netstat.terminationHandler = { (_) in
        grep.launch()
    }
    netstat.launch()

    let data = pipe2.fileHandleForReading.readDataToEndOfFile()
    guard let output = String(data: data, encoding: .utf8) else { return }
    Swift.print(output)
}

こんな感じでPipeを2個用意して，grepの方のstandardInputに一つ目のコマンドの出力結果のPipeを入れて，一つ目の実行結果の後にgrepを実行するようにterminationHandlerを登録してあげればOKです．

さらにgrepしたい時も同様の手順でOKです．

func en0() {
    // $ netstat -rnf inet | grep default | grep en0
    let pipe1 = Pipe()
    let pipe2 = Pipe()
    let pipe3 = Pipe()

    let netstat = Process()
    netstat.launchPath = "/usr/bin/env"
    netstat.arguments = ["netstat", "-rnf", "inet"]
    netstat.standardOutput = pipe1

    let grep = Process()
    grep.launchPath = "/usr/bin/grep"
    grep.arguments = ["default"]
    grep.standardInput = pipe1
    grep.standardOutput = pipe2

    let grep2 = Process()
    grep2.launchPath = "/usr/bin/grep"
    grep2.arguments = ["en0"]
    grep2.standardInput = pipe2
    grep2.standardOutput = pipe3

    grep.terminationHandler = { (_) in
        grep2.launch()
    }
    netstat.terminationHandler = { (_) in
        grep.launch()
    }
    netstat.launch()

    let data = pipe3.fileHandleForReading.readDataToEndOfFile()
    guard let output = String(data: data, encoding: .utf8) else { return }
    Swift.print(output)
}

追記

いろいろやっていたらもっと強い方法を見つけてしまいました．

func runShell(_ args: String) {
    let process = Process()
    process.launchPath = "/bin/sh"
    process.arguments = ["-c", args]

    let pipe = Pipe()
    process.standardOutput = pipe
    process.launch()

    let data = pipe.fileHandleForReading.readDataToEndOfFile()
    guard let output = String(data: data, encoding: .utf8) else { return }
    Swift.print(output)
}

runShell("ifconfig | grep broadcast")

シェルを文字列を引数にして叩けばなんでもありやないか...

Swift：Processでgrepする

追記