How to (terminal) cd in folder from ruby script

Question

I\'d like to know if it\'s possible to change the current terminal directory from where I\'m executing my ruby script.

For example, if I\'m executing the script from

Answer 1

This isn't possible, to my knowledge, since they're different processes. If you need to affect the Ruby script's parent process (Bash), Bash will need to source something. So you could have your Ruby script output some bash commands, then have a Bash wrapper that source's Ruby's output.

Try this as an example, in Bash:

`ruby -e 'puts "cd /tmp"'` | source /dev/stdin

But this will only work in Bash 4.0.

EDIT:

Actually, you can do this with eval instead of source in Bash 3:

eval $(ruby -e'puts "cd /tmp"')

Answer 2

Maybe slightly easier,

You can use exec in combination with Maerics post about creating a new bash shell inside of ruby to achieve this.

exec ruby -e "Dir.chdir( 'mydir' ); exec 'bash'"

exec will replace the parent process(shell) with the child process (ruby), thus the shell no longer exists (no need to exit).

At the end of the ruby routine bash is fired up (again with exec this time in ruby) in the new directory and replaces the ruby process.

Answer 3

Midnight Commander does this, by using a shell alias and a wrapper-script.

The wrapper is for cd'ing to a directory determined by the contents of a file written by mc(1) at exit, and the alias is used to source the wrapper, which makes it execute in the login shell, instead of the subshell that would have been forked, had the script been launched normally.

All in all, this lets it change the current working directory on exit.

To do this, you'd need to duplicate the alias/wrapper functionality. See http://midnight-commander.org/browser/contrib for how they did it.

Answer 4

I doubt there is a straightforward way to do this.

When you launch a program from your login shell, underneath the hood it's doing a fork/exec which means a new (child) process is created (which has its own environment, such as current working directory) and it's standard input/output/error streams are associated with the (parent) shell process. So when your script calls Dir.chdir it changes the current working directory for the script (child) process, not the parent.

Perhaps your script could launch a new shell before it exits, so it looks like your terminal has changed directory. Although, you'd have to exit from that extra shell before exiting your terminal session...