registerHook.sh

#! /bin/bash
#  (MIT, GPL3+) Alberto Salvia Novella (es20490446e)


main () {
    checkPermissions
    insertHook "colors" "base"
}


checkPermissions () {
    user=$(id -u)

    if [ "${user}" -ne 0 ]; then
        (>&2 echo "Not enough permissions")
        echo "Type 'sudo' or 'su;' before this command"
        exit 1
    fi
}


execute () {
    function="${1}"
    command="${2}"
    error=$(eval "${command}" 2>&1 >"/dev/null")

    if [ ${?} -ne 0 ]; then
        echo "${function}: $error"
        exit 1
    fi
}


insert () {
    string="${1}"
    toInsert="${2}"
    separator="${3}"

    if [ "${string}" != "" ]; then
        string=$(echo "${string}""${separator}")
    fi

    echo "${string}""${toInsert}"
}


insertAfter () {
    string="${1}"
    toInsert="${2}"
    after="${3}"
    separator="${4}"

    IFS="${separator}" read -r -a string <<< "$string"

    for element in "${string[@]}"; do
        if [ "${lastElement}" = "${after}" ] && [ "${element}" != "${toInsert}" ]; then
            inserted=$(insert "${inserted}" "${toInsert}" "${separator}")
        fi

        inserted=$(insert "${inserted}" "${element}" "${separator}")
        lastElement="${element}"
    done

    echo "${inserted}"
}


insertHook () {
    toInsert=${1}
    after=${2}

    file="/etc/mkinitcpio.conf"
    hooks=$(variableInFile "HOOKS" "${file}")
    inserted=$(insertAfter "${hooks}" "${toInsert}" "${after}" " ")
    modifyVariableInFile "HOOKS" "${inserted}" "${file}"
    updateInitImage
}


modifyVariableInFile () {
    variable="${1}"
    content="${2}"
    file="${3}"

    if [ ! -f "${file}" ]; then
        echo "modifyVariableInFile: file doesn't exist: ${file}"
        exit 1
    fi

    sed -i "s/^${variable}\=.*/${variable}=\"${content}\"/" "${file}"
}


updateInitImage () {
    execute "updateInitImage" "mkinitcpio"
}


variableInFile () {
    variable="${1}"
    file="${2}"

    source "${file}"
    eval value=\$\{${variable}\}
    echo "${value}"
}


main