install-cron.sh

#!/bin/bash
#
# Install cron jobs from the script header.
#
# E.g. "# CRON-HOURLY    :/usr/local/bin/example.sh"
# Cron syntax: "# CRON.D         :09,39 *	* * *	root	/usr/local/bin/example.sh"
# See: man 5 crontab
#
# VERSION       :0.2
# DATE          :2014-12-26
# AUTHOR        :Viktor Szépe <viktor@szepe.net>
# LICENSE       :The MIT License (MIT)
# URL           :https://github.com/szepeviktor/debian-server-tools
# BASH-VERSION  :4.2+


Die() {
    local RET="$1"
    shift
    echo -e $@ >&2
    exit "$RET"
}

Valid_cron_interval() {
    local QUESTION="$1"

    for VALID in cron.daily cron.hourly cron.monthly cron.weekly; do
        if [ "$QUESTION" == "$VALID" ]; then
            return 0
        fi
    done

    return 1
}

SCRIPT="$1"

if [ "$(id --user)" -ne 0 ]; then
    Die 1 "Only root is allowed to install cron jobs."
fi

if ! [ -f "$SCRIPT" ]; then
    Die 2 "Please specify an existing script."
fi

#TODO rewrite: loop through valid crons and `head -n 30 "$SCRIPT"|grep -i "^# ${CRON}")"|cut -d':' -f2 >> "$CRON_FILE"`
CRON_JOBS="$(head -n 30 "$SCRIPT" | grep -i "^# CRON")"

[ -z "$CRON_JOBS" ] && Die 3 "No cron job in script."

declare -i JOB_ID="0"
declare -i JOB_ID_D="0"

while read -r JOB; do
    CRON_INTERVAL="$(echo "$JOB" | cut -d' ' -f 2 | tr '[:upper:]' '[:lower:]')"
    CRON_INTERVAL="${CRON_INTERVAL/-/.}"

    if Valid_cron_interval "$CRON_INTERVAL"; then
        CRON_FILE="/etc/${CRON_INTERVAL}/$(basename "${SCRIPT%.*}")$(( ++JOB_ID ))"
        echo "#!/bin/bash" > "$CRON_FILE"
        echo "$JOB" | cut -d ":" -f 2 >> "$CRON_FILE"
        chmod 755 "$CRON_FILE"
        echo "[cron] ${SCRIPT} -> ${CRON_FILE}"
    elif [ "$CRON_INTERVAL" == cron.d ]; then
        CRON_FILE="/etc/cron.d/$(basename "${SCRIPT%.*}")"
        if [ $(( ++JOB_ID_D )) -eq 1 ]; then
            # initialize cron.d file
            echo -n > "$CRON_FILE"
        fi
        echo "${JOB}" | cut -d':' -f 2 >> "$CRON_FILE"
        echo "[cron] ${SCRIPT} -> ${CRON_FILE}"
    else
        Die "Invalid cron interval in script header: (${CRON_INTERVAL})"
    fi
done <<< "$CRON_JOBS"