How to run an external program in a target directory

[nstgc]

I want to run an external program in several different directories in parallel. In Clojure, to run an external program in a given directory, I would run (sh "pwd" :dir "some/path") and get back some/path. How would this be done in Janet?

[ianthehenry]

This isn't really an answer, but I don't know of a nice way to do this right now.

Neither os/spawn nor https://github.com/andrewchambers/janet-posix-spawn support posix_spawn_file_actions_addchdir_np or which is kinda what you want. You can os/cd before you spawn each subprocess if you don't care about mangling your current working directory (or are willing to restore it).

I think it would probably be reasonable to add posix_spawn_file_actions_addchdir_np to os/spawn? But I don't know what platforms it's actually supported on / what that ifdef would look like.

https://github.com/andrewchambers/janet-sh is a nice subprocess DSL but it doesn't have a way to spawn subprocesses without synchronously awaiting them (you can do this with the janet-posix-spawn library it's based on; I don't think you can asynchronously await the native os/spawn but I could be wrong and it seems like you should be able to). It might be reasonable to add a $& for direct control over the spawned process... but it would be better if janet-sh just used the event loop so you could use ev/spawn to run multiple subprocesses concurrently for free.

[nstgc]

Ah, okay. I figured parrelel cds would be one of those side effects that can really mess up a script.

I do suppose that in this case I could just run a separate instance in each directory, then another script to tie it all together afterwards.

Thanks. it's hard keeping up with all the new stuff in Janet sometimes.