Shell Programming Case Study #4

#!/bin/sh
# case study #4
# how to ask for user input until valid input is given.
# exit if too many wrong answers

LIMIT=7
CNT=0

while :
do
   CNT=`expr $CNT + 1`
   if [ $CNT -gt $LIMIT ]
   then
      break
   fi
   echo "\nEnter your full name: \c"
   read NAME

   if [ -z "$NAME" ]
   then
      echo "Error: missing input" >&2
      continue
   fi

   CHECK=`echo "$NAME" | grep '.\{31\}'`
   if [ -n "$CHECK" ]
   then
      echo "Error: name exceeds 30 characters" >&2
      continue
   fi

   CHECK=`echo "$NAME" | grep '[^ ] [^ ]'`
   if [ -z "$CHECK" ]
   then
      echo "Error: you must supply both first and last name" >&2
      continue
   fi
    
   break
done

if [ $CNT -gt $LIMIT ]
then
   echo "Error: too many invalid inputs. Program aborted." >&2
   exit 15
fi

echo "Nice to meet you $NAME"