Applying bash function to each file in subfolder recursively

Question

I am trying to write a script that will apply a bash function for each file in a directory recursively. For example if the directory tests had all my files and sub-directories in it, the script

find tests -type f -print0 | xargs -0 echo

Works perfectly. Now I want to be able to apply a bash function rather than just echo, so I came up with something like this:

function fun() {
    echo $1
}

export -f fun

find tests -type f -print0 | xargs -0 bash -c 'fun "$@"'

However this only outputs a single file in tests, where before it output all the files. I would expect these two to run the same no?

Answer 1

Use a shell script.

To quote from this excellent answer:

Do other programs besides your shell need to be able to use it? If so, it has to be a script.

As already noted in other answers, it may be possible to work around this by exporting the function, but it's certainly a lot simpler to just use a script.

#!/bin/bash
# I'm a script named "fun"!  :)
printf '%s\n' "$@"

Then you just put the fun script somewhere in your PATH (perhaps in ~/bin), make sure it's executable, and you can run:

find tests -type f -exec fun {} +

Answer 2

If you use GNU Parallel it looks like this:

function fun() {
    echo "$@"
}
export -f fun

find tests -type f -print0 | parallel -0 -Xj1 fun

Answer 3

There two ways to solve this issue: you could either tell xargs to run command with only one argument at a time using -n1 or loop for all arguments inside your function fun:

function fun() { echo $1 }
export -f fun
find tests -type f -print0 | xargs -n1 -0 bash -c 'fun "$@"' --

or

function fun() { while [ -n "$1" ]; do echo $1; shift; done }
export -f fun
find tests -type f -print0 | xargs -0 bash -c 'fun "$@"' --