Shell Programming and Scripting

A=1

while [ $A -le $z ]
do

1.check the file output,if the file output is N then keep on checking till the count every 2minutes.)sleep is used here with the count expr for A.
2.if not then check the output is Y, if yes then execute main script and come out.

sleep 120
A=`expr $A + 1`
done

if [ expr ]
then
  statements
fi

while [ $A -le $z ]
do
  if [ $(cat file) == "Y" ] # We're cat-ing the file only because we know it contains one character only. Otherwise this is  a bad trick
  then
    <execute_main_script>
  fi
  sleep 120
  A=`expr $A + 1`
done

while [ $A -le $z ]
do
  read line < file # efficiently read the first line
  if [ "$line" = "Y" ]
  then
    /path/to/main_script
    break # break the loop
  fi
  sleep 120
  A=`expr $A + 1`
done