What is the purpose of the : (colon) GNU Bash builtin?

Question

What is the purpose of a command that does nothing, being little more than a comment leader, but is actually a shell builtin in and of itself?

It\'s slower than inse

Answer 1

Another way, not yet mentioned here is the initialisation of parameters in infinite while-loops. Below is not the cleanest example, but it serves it's purpose.

#!/usr/bin/env bash
[ "$1" ] && foo=0 && bar="baz"
while : "${foo=2}" "${bar:=qux}"; do
    echo "$foo"
    (( foo == 3 )) && echo "$bar" && break
    (( foo=foo+1 ))
done