cd可执行文件的位置 [英] Location of cd executable

问题描述

我了解到，使用exec()调用发出的命令的可执行文件应该存储在PATH变量的一部分中.

I read that the executables for the commands issued using exec() calls are supposed to be stored in directories that are part of the PATH variable.

因此，我在/bin中找到了ls, chmod, grep, cat的可执行文件.

Accordingly, I found the executables for ls, chmod, grep, cat in /bin.

但是，我找不到cd的可执行文件.

However, I could not find the executable for cd.

它在哪里?

推荐答案

一个进程只能影响其自己的工作目录.当可执行文件由外壳执行时，它作为子进程执行，因此cd可执行文件(如果存在)将在不影响父进程(外壳)的情况下更改该子进程的工作目录，因此cd命令必须实现为内置的shell，实际上是在shell自己的进程中执行的.

A process can only affect its own working directory. When an executable is executed by the shell it executes as a child process, so a cd executable (if one existed) would change that child process's working directory without affecting the parent process (the shell), hence the cd command must be implemented as a shell built-in that actually executes in the shell's own process.

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