问题:

Where can I find the source code for Unix environment's cd command?

I want to know how the command is implemented.

回答1:

Here is a complete explanation how cd works: http://web.archive.org/web/20090515201659/http://www.cs.ucr.edu/~brett/cs153_w02/syscall.html

The cd Unix command just calls chdir and examines the error codes.

回答2:

To see the source for the bash cd command, for example:

Download the bash source from http://ftp.gnu.org/gnu/bash/
Extract the source
Examine bash-./builtins/cd.def, where "." represents the version you downloaded (e.g. 4.2). This is the file from which cd.c is created, according to the comment at the top of the file.

回答3:

cd is usually built-in in the shell, you should just look at the code of any shell, e.g. bash, or ash.

The cd command should be ultimately based on the chdir() function, but if you're interested in all the command line expansions, then the source is the shell.

http://en.wikipedia.org/wiki/Comparison_of_computer_shells