#!/usr/bin/env bash # - Read first charactor of a file: # - # - head -c1 deb_major_version="" is_number() { return $(test ! -z "${1##*[!0-9]*}" > /dev/null 2>&1); # - also possible # - #[[ ! -z "${1##*[!0-9]*}" ]] && return 0 || return 1 #return $([[ ! -z "${1##*[!0-9]*}" ]]) } if [[ -f "/etc/debian_version" ]]; then deb_major_version=$(head -c1 /etc/debian_version) if is_number $deb_major_version ; then echo -e "\n\tDebian Major Version: $deb_major_version\n" else echo -e "\n\tNo numeric Version given. Debian Version: $(head -1 /etc/debian_version)\n" fi else echo -e "\nFile '/etc/debian_version' not found" fi exit 0