Bash function to parse major, minor and patch versions from a semantic versioning string

semver.sh

#!/bin/bash
#
# Function that parses semantic versioning striings of
# the form:
#   MAJOR.MINOR.PATCH([+-].*)?
#

# Parse the major, minor and patch versions
# out.
# You use it like this:
#    semver="3.4.5+xyz"
#    a=($(parse_semver "$semver"))
#    major=${a[0]}
#    minor=${a[1]}
#    patch=${a[2]}
#    printf "%-32s %4d %4d %4d\n" "$semver" $major $minor $patch
function parse_semver() {
    local token="$1"
    local major=0
    local minor=0
    local patch=0

    if egrep '^[0-9]+\.[0-9]+\.[0-9]+' <<<"$token" >/dev/null 2>&1 ; then
        # It has the correct syntax.
        local n=${token//[!0-9]/ }
        local a=(${n//\./ })
        major=${a[0]}
        minor=${a[1]}
        patch=${a[2]}
    fi
    
    echo "$major $minor $patch"
}

function parse_semver_test() {
    local versions=(
        '1.2.3'
        '1.2.4+foobar'
        '1.2.5-alpha01'
        'not-a-semver'  # not valid
        '2.3.4abc'      # not strictly semver but it works'
        'a1.2.3'        # not valie
    )
    for version in ${versions[@]} ; do
        a=($(parse_semver "$version"))
        major=${a[0]}
        minor=${a[1]}
        patch=${a[2]}
        printf "%-32s %4d %4d %4d\n" "$version" $major $minor $patch
    done
}

parse_semver_test