foo.sh

#!/usr/bin/env bash
#
#   parrot-upgrade
#
# DESCRIPTION:
#   Upgrade a parrotOS system to the latest rolling release using sane defaults
#
# OUTPUT:
#   plain text
#
# PLATFORMS:
#   ParrotOS
#
# DEPENDENCIES:
#   apt
#   sudo
#
# USAGE:
#
# EXAMPLES:
#   sudo parrot-upgrade
#
# NOTES:
#
# LICENSE:
#   Copyright 2020 ParrotOS
#   Released under the the MIT license; see LICENSE
#   for details.
#

set -eo pipefail

_OK() {
    declare desc="OK exit status"
    # TODO print a status summary
    echo Status: Update Successful
    exit 0
}

_CRITICAL() {
    declare desc="Critical exit status"
    # TODO drop the error message here
    echo Status: Update Failed
    exit 2
}

_UNKNOWN() {
    decalre desc="Unknow exit status"
    # TODO drop the error message here
    echo Status: Update Failed
    exit 3
}

show_help() {
    declare desc="Help command"
    cat <<EOF
    sudo parrot-upgrade
EOF
}

die() {
    declare desc="standard error handling"
    printf '%s\n' "$1" >&2
    _UNKNOWN
}

function update {
    apt_cmd="/usr/local/bin/apt"
    dpkg_cmd="/usr/bin/dpkg"
    echo_cmd="/usr/bin/echo"

    "$apt_cmd" update || "$echo_cmd" failed to update index lists
    "$dpkg_cmd" --configure -a || "$echo_cmd" failed to fix interrupted upgrades
    "$apt_cmd" --fix-broken --fix-missing install || "$echo_cmd" failed to fix conflicts
    "$apt_cmd" -y --allow-downgrades --fix-broken --fix-missing dist-upgrade
}

function main {
    declare desc="Main entry point to the script"

    local DEBIAN_FRONTEND="noninteractive"
    local DEBIAN_PRIORITY="critical"
    local DEBCONF_NOWARNINGS="yes"

    export "$DEBIAN_FRONTEND" "$DEBIAN_PRIORITY" "$DEBCONF_NOWARNINGS"

    # Update the system
    update

    _OK
}

while :; do
     case $1 in
        -h| -\?|--help)
             show_help
             exit
             ;;
        --)
             shift
             break
             ;;
        -?*)
             printf 'WARN: Unknown option (ignored): %s\n' "$1" >&2
             ;;
        *)
             break
     esac
     shift
 done

main