shell - 终端 cd 命令不适用于 Scala 脚本

Question

我需要从 Scala 脚本运行 shell 命令，为此我使用以下代码段:

import scala.sys.process.{Process, ProcessIO}

val command = "ls /tmp"
val process = Process(command)

val processIO = new ProcessIO(_ => (),
    stdout => scala.io.Source.fromInputStream(stdout).getLines.foreach(println),
    _ => ())
process.run(processIO)

代码工作正常。我想知道为什么我得到

java.io.IOException: Cannot run program "cd": error=2, No such file or directory

一旦我将命令更改为 cd /tmp && ls IMO 相当于 ls /tmp ?

Answer 1

来自 Wikipedia on cd command :

[...] on Unix systems cd calls the chdir() POSIX C function. This means that when the command is executed, no new process is created to migrate to the other directory as is the case with other commands such as ls. Instead, the shell itself executes this command.

那里甚至有关于 Java 的引用:

[...] neither the Java programming language nor the Java Virtual Machine supports chdir() directly; a change request remained open for over a decade while the team responsible for Java considered the alternatives, though by 2008 the request was denied after only limited support was introduced [...]

自己试试:

$ which ls
/bin/ls
$ which cd
$

简单来说，cd不是您可以运行的程序(进程)(如 /bin/ls )——它更像是一个命令行指令。

你想达到什么目的？ Changing the current working directory in Java?或者更改您刚刚创建的进程的工作目录？