dpkg-vercomp.sh

#!/bin/bash
# http://stackoverflow.com/questions/4023830/bash-how-compare-two-strings-in-version-format

# A script to compare version/release of packages

vercomp () {
	a=$(printf "%s\n" "$1" | sed -e 's/\+/\./g')
	b=$(printf "%s\n" "$2" | sed -e 's/\+/\./g')

	# echo "Version A=$a Version B=$b" # debug

    if [[ $a == $b ]]
    then
        return 0
    fi
    local IFS=.
    local i ver1=($a) ver2=($b)
    # fill empty fields in ver1 with zeros
    for ((i=${#ver1[@]}; i<${#ver2[@]}; i++))
    do
        ver1[i]=0
    done
    for ((i=0; i<${#ver1[@]}; i++))
    do
        if [[ -z ${ver2[i]} ]]
        then
            # fill empty fields in ver2 with zeros
            ver2[i]=0
        fi
        if ((10#${ver1[i]} > 10#${ver2[i]}))
        then
            return 1
        fi
        if ((10#${ver1[i]} < 10#${ver2[i]}))
        then
            return 2
        fi
    done
    return 0
}

# usage:
#    vercomp $1 $2
#    case $? in
#        0) op='=';;
#        1) op='>';;
#        2) op='<';;
#    esac