UNIX for Dummies Questions & Answers

Hi Guys,
I am trying to find a way within a bash script to check a file that exists in the same directory to ensure every line starts with 44 and is 12 digits long. If it doesn't then print some sort of text advising of the error and stop the script from going any further. If all lines start with 44 and are 12 digits long then continue with the script. Im fairly new to this so any help would really be appreacited.

Thanks

Proposal:

Code:

if grep -nv '^44[0-9]\{10\}$' filename
then
 echo 'Please check the above line(s).'
 exit
fi
echo ...