Script to check if an entry present on crontab, if not create new one

Question

I want to make an entry in crontab that will optimize mysql database, so I am writing a script that will check if it is already present, else it will be created.

The problem I'm facing is when I check for entry it is returning many unwanted entries, to be specific all directories, files as output, present in the directory where I am executing the script.

My overall script looks like:

check=`crontab -l | grep -i "ABC"`
 if [ -z "$check" ];
 then
     #echo " Adding opt to crontab "
     crontab -l > ./tmpfile

            echo "0 * * * * /bin/bash /usr/bin/mysqlcheck --all-databases -o --user=<user> --password=<pwd> 2>&1  >> ./tmpfile

     crontab ./tmpfile
     rm tmpfile
     echo "ABC has been successfully added to crontab"
     exit 1
 else
    echo "ABC already exists in crontab "
    exit 1
 fi