I don't understand.

If the first line of the file txtif.out is not x followed by a <newline> character, your script will exit without printing anything. Otherwise, you have an infinite loop printing three lines each time through the loop.

If you want to break out of the loop, you either need to change the value of var1 to something other than x inside the loop, or execute a break statement in the loop (which you code cannot do since the value of var1 never changes in your loop).

If something inside your loop is changing the contents of txtif.out (which nothing currently does) or in some external process is changing the contents of txtif.out and you want to the loop to stop when that happens, you would need something more like:

Code:

read var1 < txtif.out
while  [ "$var1" = x ]
do
  echo file1
  echo file2
  echo y txtif.out 
  read var1 < txtif.out
done

exit  0

If you think that the command:

Code:

  echo y txtif.out

would change the contents of txtif.out to the string y; it does not. And, if you think that changing the contents of txtif.out will affect your infinite loop; it will not. That would be done by:

Code:

  echo y > txtif.out

but, if you just want to execute a loop once, why have a loop. An if statement would be more appropriate:

Code:

read var1 < txtif.out
if  [ "$var1" = x ]
then
  echo file1
  echo file2
  echo y txtif.out  # or maybe you wanted echo y > txtif.out instead.
fi

exit  0