In a bash script, how do I sanitize user input?

Question

I\'m looking for the best way to take a simple input:

echo -n \"Enter a string here: \"
read -e STRING

and clean it up by removing non-alph

Answer 1

For Bash >= 4.0:

CLEAN="${STRING//_/}" && \
CLEAN="${CLEAN// /_}" && \
CLEAN="${CLEAN//[^a-zA-Z0-9]/}" && \
CLEAN="${CLEAN,,}"

This is especially useful for creating container names programmatically using docker/podman. However, in this case you'll also want to remove the underscores:

# Sanitize $STRING for a container name
CLEAN="${STRING//[^a-zA-Z0-9]/}" && \
CLEAN="${CLEAN,,}"