Based on John Kelly’s original script:
| #!/bin/sh | |
| # | |
| # Provides missing crontab editing | |
| # Note: Synology crond requires arguments separated by a TAB character | |
| # and the crontab user field only supports root. These requirements are | |
| # enforced by this script. | |
| # | |
| # John Kelly, 2013-05-03 | |
| # Richard Cook, 2014-02-21 | |
| # | |
| SCRIPTPATH=$(readlink -f $0) | |
| SCRIPTNAME=$(basename "$SCRIPTPATH") | |
| # Default path to crontab file | |
| CRONTABPATH=/etc/crontab | |
| # Failed edits are kept in this file | |
| CHKCRON=/etc/crontab.chk | |
| # Previous version | |
| TMPNAME=/etc/crontab.old | |
| # Max versions to keep. One or greater | |
| MAXVER=10 | |
| # Set to your editor of choice | |
| EDITOR=nano | |
| usage() { | |
| echo -e "Usage: $SCRIPTNAME [-l | -v | -f | -e | -h]\n" | |
| } | |
| # Check for selected editor. Default to vi | |
| EDITOR=$(/usr/bin/which $EDITOR 2>&1) | |
| [[ ! -x "$EDITOR" ]] && EDITOR=/bin/vi | |
| show_help() { | |
| echo -e 'Provides basic access to the crontab file' | |
| echo -e 'with simple format checks\n' | |
| usage | |
| echo ' -l : Lists the current contents of the root crontab file' | |
| echo ' -v : Verifies the current contents of the root crontab file' | |
| echo ' -f : Refreshes the cron daemon' | |
| echo ' -e : Edits the crontab file and refreshes the cron daemon if' | |
| echo ' the file is actually changed; otherwise does nothing' | |
| echo -e ' -h : Shows this help text\n' | |
| } | |
| verify_crontab() { | |
| # Synocron is very picky. Check the file format | |
| ( # Start of output redirection block | |
| IFS=" | |
| " | |
| cat $1 | \ | |
| while read LINE; do | |
| # Find out if empty or the first character is a # | |
| echo "$LINE" | awk '{print $1}' | egrep "^#|^$" > /dev/null 2>&1 | |
| if [[ $? = 0 ]]; then | |
| # Copy over comment/blank lines exactly | |
| echo "$LINE" | |
| else | |
| unset IFS | |
| # test convert using tabs to compare results | |
| echo "$LINE" | while read MIN HO MD MO WD WH COM; do | |
| echo -e "$MIN\t$HO\t$MD\t$MO\t$WD\troot\t$COM" | |
| done | |
| IFS=" | |
| " | |
| fi | |
| done | |
| ) > $2 # end of output redirection block | |
| # Compare files and return the result | |
| diff $1 $2 > /dev/null 2>&1 | |
| return $? | |
| } | |
| restart_cron() { | |
| echo 'Refreshing cron daemon.' | |
| SYNOSERVICE=/usr/syno/sbin/synoservice | |
| if [ -f $SYNOSERVICE ]; then | |
| $SYNOSERVICE --restart crond | |
| return | |
| fi | |
| CRONDRC=/usr/syno/etc/rc.d/S04crond.sh | |
| if [ -f $CRONDRC ]; then | |
| $CRONDRC stop | |
| $CRONDRC start | |
| return | |
| fi | |
| echo 'Don'"'"'t know how to restart cron service.' | |
| exit 1 | |
| } | |
| archive_crontabs() { # Keep up to MAXVER versions | |
| ARCVER=$MAXVER | |
| while [[ $ARCVER -gt 1 ]]; do | |
| PRVVER=$(expr $ARCVER - 1) | |
| if [ -f $TMPNAME.$PRVVER ]; then | |
| mv -f $TMPNAME.$PRVVER $TMPNAME.$ARCVER | |
| fi | |
| ARCVER=$PRVVER | |
| done | |
| cp $TMPNAME $TMPNAME.1 | |
| } | |
| edit_crontab() { | |
| archive_crontabs | |
| cp $1 $TMPNAME | |
| $EDITOR $1 | |
| diff $1 $TMPNAME > /dev/null 2>&1 | |
| if [[ $? = 0 ]]; then | |
| echo "No changes made. Doing nothing." | |
| else | |
| if verify_crontab $1 $2; then | |
| echo 'Crontab altered.' | |
| echo "Previous version saved in $TMPNAME" | |
| rm -f $2 | |
| restart_cron | |
| else | |
| echo 'Crontab file is NOT in the correct Synology format.' | |
| echo 'Please use TABs between fields and specify root in sixth field.' | |
| echo "Your version is saved in $2. Restoring original version." | |
| diff $1 $2 | cat -A | |
| cat $1 > $2 | |
| cat $TMPNAME > $1 | |
| fi | |
| fi | |
| exit 0 | |
| } | |
| check_command() { | |
| if [[ "$COMMAND" != '' ]]; then | |
| echo -e 'You must specify exactly one command.\n' | |
| usage | |
| exit 1 | |
| fi | |
| } | |
| COMMAND= | |
| while getopts p:lvfeh FLAG; do | |
| case $FLAG in | |
| p) CRONTABPATH=$(readlink -f $OPTARG);; | |
| l) check_command; COMMAND=l;; | |
| v) check_command; COMMAND=v;; | |
| f) check_command; COMMAND=f;; | |
| e) check_command; COMMAND=e;; | |
| h) check_command; COMMAND=h;; | |
| esac | |
| done | |
| if [[ "$COMMAND" = '' ]]; then | |
| usage | |
| exit 1 | |
| fi | |
| case $COMMAND in | |
| l) | |
| echo "crontab at $CRONTABPATH" | |
| cat $CRONTABPATH;; | |
| v) | |
| TEMPPATH=$(mktemp) | |
| if verify_crontab $CRONTABPATH $TEMPPATH; then | |
| echo "crontab at $CRONTABPATH is valid" | |
| else | |
| echo "crontab at $CRONTABPATH is not valid:" | |
| diff $CRONTABPATH $TEMPPATH | cat -A | |
| fi | |
| rm $TEMPPATH;; | |
| f) restart_cron;; | |
| e) edit_crontab $CRONTABPATH $CHKCRON;; | |
| h) show_help;; | |
| esac |
| The MIT License (MIT) | |
| Copyright (c) 2014 Richard Cook | |
| Permission is hereby granted, free of charge, to any person obtaining a copy of | |
| this software and associated documentation files (the "Software"), to deal in | |
| the Software without restriction, including without limitation the rights to | |
| use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of | |
| the Software, and to permit persons to whom the Software is furnished to do so, | |
| subject to the following conditions: | |
| The above copyright notice and this permission notice shall be included in all | |
| copies or substantial portions of the Software. | |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS | |
| FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR | |
| COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER | |
| IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | |
| CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
My version adds a -v command for verifying crontabs without installing them.
Content © 2025 Richard Cook. All rights reserved.