Use built-in Change Directory(cd) command

[carloseduardosx]

The problem

When we use command to execute any built-in command, first it'll look inside the PATH variable for any command that the argument passed may match, if it finds any command that match, then it'll execute that command, if it doesn't find any command in the PATH, then it'll look for built-in commands of your command shell and then execute it.

OSX has a cd command located at /usr/bin/cd and in general it's inside the PATH variable. But if you use ZSH or any other shell, you should be using their built-in commands.

For example, for who use ZSH, the built-in commands may be located at /usr/local/Cellar/zsh/<zsh_version>/share/zsh/functions. And in this case the built-in cd command it's inside this folder, more precisely at /usr/local/Cellar/zsh/5.4.2_1/share/zsh/functions/_cd.

As you can see on zsh repository, the cd command has the -q option.

The solution

So, the solution is to use the builtin command, which looks directly inside the built-in commands, skipping the PATH part.

Fixes #144

[carolynvs]

Sweet! Someone who knows what's going on with shells! 🎉 ❤️ Thanks for the explanation of command vs builtin.

Can you help me understand what is executed if we didn't use either builtin or command, and just called cd directly? Do you know if all the shells support builtin?

I would absolutely love to get this fixed ASAP. I just want to make sure that if we make this change that it will work for all shells (not just zsh).

[carloseduardosx]

The main reason to use command or builtin is because they look directly inside built-in commands, skipping functions and alias. In case of the user have an alias or function with name cd, when we execute the cd command, the shell will call one of them, in this case our script probably won't work.

[carloseduardosx]

About the builtin command, I can't have 100% sure that all command shells have this command as built-in, but the two most used command shell have it, which is: bash and zsh

[carloseduardosx]

@carolynvs For better security, I added a check for the builtin command before executing it. Now, in case of the shell doesn't have the builtin command, we use the cd command alone, this should solve the problem.

[rgbkrk]

👀

[rgbkrk]

Yeah this looks like some good tradeoffs.

[carolynvs]

Is there a reason why pwd (and rm later down in the file) aren't also getting the same treatment as cd?

If we need it in both plances, perhaps we can have a variable $CMD_PREFIX or something like that which is set to either builtin or ""?

[carloseduardosx]

The reason why the pwd and rm programs aren't being invoked by the builtin is because the OSX doesn't have a specific built-in command for them, like it have for cd.

[carolynvs]

Thank you for the fix and all the explanations! 🎉