Compare string versions in bash

README.md

version_cmp()

Simple function to (properly) compare version strings in bash

The problem

You can not do alphabetic comparison:

1.23.4 < 1.3.4 => FALSE

Usage

version_cmp  1.2.3    4.5.6
version_cmp  1.5.6.7  1.5.6

if [[ $(version_cmp $rsync_version 2.5.7) -lt 0 ]]; then
    ERROR "Invalid version of rsync. 2.5.7 or more required"
fi

(Just to keep Google happy: By Toni Homedes i Saun)

bash-version-cmp.sh

#-----------------------------------------------------------------------------
#
#   Compare two version strings
#
#   @param [in]     a           Version string to compare
#   @param [in]     b           Version string to compare
#
#   Usage:
#       version_cmp  1.2.3    4.5.6
#       version_cmp  1.5.6.7  1.5.6
#
#   @return -1, 0 or 1
#
#-----------------------------------------------------------------------------
version_cmp() {
    local a="$1" b="$2"
    local -i fa fb

    while true; do

	fa="${a%%.*}"
	fb="${b%%.*}"

	((fa != fb)) && break

	a="${a#$fa}"; a="${a#.}"
	b="${b#$fb}"; b="${b#.}"

	if [[ -z $a && -z $b ]]; then
	    echo 0
	    return
	fi
    done
    ((fa > fb)) && echo 1 || echo -1
}