How do I validate that a version number is valid using a regexp in bash?

Question

I am trying to validate that the version number is matching a version pattern but it seems that the check fails for some weird reason.

#!/bin/bash
VERSION="1.2.3"
if [[ $VERSION =~ ^(\d+\.)?(\d+\.)?(\*|\d+)$ ]]; then
 echo "INFO:<-->Version $VERSION"
else
 echo "ERROR:<->Unable to validate package version: '$VERSION'"
 exit 1
fi

Answer 1

You should use [0-9] or [[:digit:]] in Bash instead of \d (as Bash does not support this shorthand character class), and I suggest shortening the pattern with the help of a limiting quantifier and putting the pattern into a variable:

#!/bin/bash
VERSION="1.2.3"
rx='^([0-9]+\.){0,2}(\*|[0-9]+)$'
if [[ $VERSION =~ $rx ]]; then
 echo "INFO:<-->Version $VERSION"
else
 echo "ERROR:<->Unable to validate package version: '$VERSION'"
 exit 1
fi

See the IDEONE demo

The ([0-9]+\.){0,2} parts matches 1 or more digits followed with a literal dot 0, 1, or 2 times.