poll for something and exit when good

poller.sh

#!/bin/bash

POLL_INTERVAL=1
TIMEOUT_COUNT=5
COUNTER=1
FILE="stop.txt"

printf "waiting for stop.txt to appear"

while true; do
  if [ $COUNTER -gt $TIMEOUT_COUNT ]
  then
    echo "too slow"
    exit 1
  fi

  if [ -f $FILE ]
  then
    echo "!"
    echo "ready"
    exit 0
  else
    printf "."
    sleep $POLL_INTERVAL
    COUNTER=$[$COUNTER +1]
  fi
done