scala-note8-process.md

Scala笔记8-进程控制

sys.process包包含了一个从字符串到ProcessBuilder对象的隐式转换。！操作符执行的就是这个ProcessBuilder对象。

object Run extends App {
  import sys.process._
  val result = "ls -al .." ! // result is 0 if command is done succeed

  // pipe the output of one program into the input of another, using the #| operator
  "ls -al .." #| "grep z" !

  // pipe the output of one program into the input of another, using the #| operator
  import java.io.File
  "ls -al .." #> new File("output.txt") !

  // To append to a file, use #>> instead:
  "ls -al .." #>> new File("output.txt") !

  // To redirect input from a file, use #<:
  "grep sec" #< new File("output.txt") !

  // You can also redirect input from a URL:
  import java.net.URL
  "grep Scala" #< new URL("http://horstmann.com/index.html") !
}

如果需要在不同的目录下运行进程，或者使用不同的环境变量，用Process对象的apply方法来构造ProcessBuilder，给出命令和起始目录，以及一串(key, value)对来设置环境变量:

import java.io.File

object Run extends App {
  import sys.process._
  val cmd = "ls -al"
  val dirName = "/tmp"
  val p = Process(cmd, new File(dirName), ("LANG", "en_US"))

  "echo 42" #| p !
}

重定向标准输出和错误输出流:

import sys.process._

object Run extends App {
  val logger = ProcessLogger(
    (o: String) => println("out " + o),
    (e: String) => println("err " + e))
  "ls -al" ! logger

  val out = new StringBuilder
  val err = new StringBuilder
  val strlogger = ProcessLogger(
    (o: String) => out.append(o),
    (e: String) => err.append(e))
  "ls -al" ! strlogger
}