Shell – Running command on multiple files within multiple directories

You can use this loop in bash:

for i in */; do zip -r "${i%/}.zip" "$i"; done

i is the name of the loop variable. */ means every subdirectory of the current directory, and will include a trailing slash in those names. Make sure you cd to the right place before executing this. "$i" simply names that directory, including trailing slash. The quotation marks ensure that whitespace in the directory name won't cause trouble. ${i%/} is like $i but with the trailing slash removed, so you can use that to construct the name of the zip file.

If you want to see how this works, include an echo before the zip and you will see the commands printed instead of executed.

Parallel execution

To run them in parallel you can use &:

for i in */; do zip -0 -r "${i%/}.zip" "$i" & done; wait

We use wait to tell the shell to wait for all background tasks to finish before exiting.

Beware that if you have too many folders in your current directory, then you may overwhelm your computer as this code does not limit the number of parallel tasks.

If you already expect them to be directories and are just checking whether they all exist, you could use the exit code from the ls utility to determine whether one or more "errors occurred":

ls "$PWD/dir1" "$PWD/dir2" "$PWD/dir3" >/dev/null 2>&1 && echo All there

I redirect the output and stderr to /dev/null in order to make it disappear, since we only care about the exit code from ls, not its output. Anything that's written to /dev/null disappears — it is not written to your terminal.