Why can't I change directories using "cd" in a script?

Question

I'm trying to write a small script to change the current directory to my project directory:

#!/bin/bash cd /home/tree/projects/java 

I saved this file as proj, added execute permission with chmod, and copied it to /usr/bin. When I call it by: proj, it does nothing. What am I doing wrong?

Answer 1

Shell scripts are run inside a subshell, and each subshell has its own concept of what the current directory is. The cd succeeds, but as soon as the subshell exits, you're back in the interactive shell and nothing ever changed there.

One way to get around this is to use an alias instead:

alias proj="cd /home/tree/projects/java" 

Answer 2

You're doing nothing wrong! You've changed the directory, but only within the subshell that runs the script.

You can run the script in your current process with the "dot" command:

. proj 

But I'd prefer Greg's suggestion to use an alias in this simple case.