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

I use it to easily enable/disable variable commands:

#!/bin/bash
if [[ "$VERBOSE" == "" || "$VERBOSE" == "0" ]]; then
    vecho=":"     # no "verbose echo"
else
    vecho=echo    # enable "verbose echo"
fi

$vecho "Verbose echo is ON"

Thus

$ ./vecho
$ VERBOSE=1 ./vecho
Verbose echo is ON

This makes for a clean script. This cannot be done with '#'.

Also,

: >afile

is one of the simplest ways to guarantee that 'afile' exists but is 0 length.