add/remove crontab entry

bash_add_delete_crontab_entry.sh

#!/bin/bash

# it can add/delete multiple times the same crontab entry
# without having to worry for duplicate entries (in case of adding) 
# or any leftovers (in case of deleting)


# THIS KEY HAS TO BE UNIQUE IN THE ENTRY TO BE ADDED/DELETED
CMD_KEY="moo"

CRONTAB="/etc/crontab"
COUNT=`grep -c ${CMD_KEY} ${CRONTAB}`;

case "$1" in
  add)
        if [ ${COUNT} -ne 0 ]; then
                echo "entry has already been added"
                exit 0
        else
                # EDIT THIS WITH YOUR ENTRY
                echo "0-59/5 * * * *  root  nohup /root/moo.sh &> /dev/null" >> ${CRONTAB}
                exit $?
        fi
        ;;
  del)
        if [ ${COUNT} -ne 0 ]; then
                sed -i '/'${CMD_KEY}'/d' ${CRONTAB}
                exit $?
        else
                echo "entry has already been deleted"
                exit $?
        fi
        ;;
  *)
        echo "unrecognized option"
        exit 2
        ;;
esac

exit 0