Bash: join pipes without deadlock

I want to list a bunch of filenames via find, pipe them through a utility (let's call this util) which outputs a new name for each input name, and then rename each file from the old name to the new. The most basic solution would be this: find . -print0 | while IFS= read -d '' -r old_name; do new_name="$(echo "$file" | util)" mv "$old_name" "$new_name" done The problem with this approach is that util is too slow to fire up for each filename separately. So the solution is to launch util only once and pipe all the filenames through this single process: find . -print0 >old_names util new_names exec {old_fd}new_names & exec {old_fd}util does input/output buffering... So my question is: what's the proper way of doing this in bash?