Bash

Usage

find . -type f -name '*.rs' -exec rename 's/\.rs$/.txt/' {} +: Find all .rs files in the current directory and subdirectories and rename them to .txt files

brew install rename has to be installed on macOS.

find . -name ".DS_Store" -exec rm -f {} +: remove all .DS_Store files from the current directory and all nested directories
find . -type d -name "target" -exec rm -rf {} +: remove all target directories from the current directory and all nested directories