Back up your crontab

backup_crontab.sh

#!/bin/bash
set -uo pipefail
IFS=$'\n\t'

if [[ $# -eq 0 ]]; then
    echo "usage: $0 <target_directory>"
    exit 1
fi
TARGET_DIR=$1

HOST=$(hostname --short)
DATE=$(date +%F)

FNAME="${HOST}_${DATE}.cron"
GLOB="${HOST}_*.cron"
LAST_FILE=$(find $TARGET_DIR -maxdepth 1 -name $GLOB | tail -n 1)

function output {
    crontab -l > ${TARGET_DIR}/${FNAME}
}

if [[ -z "$LAST_FILE" ]]; then
    # echo "No file found, writing file"
    output
else
    DIFF=$(crontab -l | diff -q - "$LAST_FILE")
    if [[ -z "$DIFF" ]]; then
        # echo "Last file is the same, touching file"
        touch "$LAST_FILE"
    else
        # echo "Last file differs, writing new file"
        output
    fi
fi