crontab

#!/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=${EDITOR}

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/synoservicectl
  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