How to implement your own cd command in your own shell [duplicate]

Answer 1

cd is not a program, it's a built-in command. The built-in command are directly built into the shell.

To implement cd, you basically need to

1. Use chdir() to change the current directory
2. Update some environment variables (like Klas Lindback said: OLDPWD and PWD)

Answer 2

In my project I have used chdir() to implement my cd command and it works. Every process has its own PWD(Present Working Directory). A shell is also a process and its default PWD is the PWD of its parent (bash shell where I have executed ./my_sh).

Answer 3

You may wish to have a look at the chdir function in unistd.h. This changes the working directory of the current process.