install-cron.sh

#!/bin/bash
#
# Install cron jobs from the script header.
#
# VERSION       :0.2.4
# DATE          :2016-02-13
# AUTHOR        :Viktor Szépe <viktor@szepe.net>
# LICENSE       :The MIT License (MIT)
# URL           :https://github.com/szepeviktor/debian-server-tools
# BASH-VERSION  :4.2+

# Usage
#
# Add a line to your script's header: "# CRON-HOURLY  :/usr/local/bin/example.sh"
# Cron.d syntax: "# CRON.D  :09,39 *	* * *	root	/usr/local/bin/example.sh"
# See: crontab(5)

Error()
{
    local RET="$1"

    shift
    echo -e "$*" 1>&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 [[ $EUID -ne 0 ]]; then
    Error 1 "Only root is allowed to install cron jobs."
fi

if [ ! -f "$SCRIPT" ]; then
    Error 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')"

if [ -z "$CRON_JOBS" ]; then
    Error 3 "No cron job in script."
fi

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%.*}")$(( ++JOB_ID ))"
        # Create simple shell script
        {
            echo "#!/bin/bash"
            echo "$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%.*}")"
        # Initialize cron.d file
        if [ $(( ++JOB_ID_D )) -eq 1 ]; then
            rm -f "$CRON_FILE"
            touch "$CRON_FILE"
        fi
        # Append job to cron.d file
        echo "${JOB}" | cut -d ":" -f 2- >> "$CRON_FILE"

        echo "[cron] ${SCRIPT} -> ${CRON_FILE}"
    else
        Error 10 "Invalid cron interval in script header: (${CRON_INTERVAL})"
    fi
done <<< "$CRON_JOBS"