Question

I have a particular command, that reacts differently depending on the content of the current working directory.
I now wish to pipe this program back to itself, back have the call happen in different directories.

In “pseudo-bash”, I want

command arg1 | cd /other dir | command arg2

I personally use bash, but if it helps to use a different shell, I’m open to suggestions. 🙂

I realize there is a very easy workaround with a temporary file or named pipe, but I want to know if there’s a way to do this in one command.

Answer 1

command arg1 | ( cd /other_dir ; command arg2 )

(…) executes a command in a subshell. cd is a shell builtin command, not a ‘real process’. ( cd X ; command ) will start a new sub-shell, cd into X, then run command. command is running as a process, but in a different directory.

Going forward it’s better to have commands that can take a directory as an argument (and if not defined, default to the current working directory). Then you could have the simple solution of command arg1 | command --dir=/other_dir arg2