[bash] Adding Counter in shell script

I have below code in my shell script which will keep on sleeping if it doesn't finds any file. And it sleeps for half an hour but currently I don't have any counter like only execute the below code 20 times and then exit the program if the files are still are not there (means don't do anything after 20 checks and exit the full script).

What's the best way to do this problem? So that I am also aware by looking at the emails that it has tried 20 times.

Hope I am clear enough.

while true; do
  if /home/hadoop/latest/bin/hadoop fs -ls /apps/hdtech/bds/quality-rt/dt=$DATE_YEST_FORMAT2 then
       echo "Files Present" | mailx -s "File Present"  -r [email protected] [email protected]
       break
  else
       echo "Sleeping for half an hour" | mailx -s "Time to Sleep Now"  -r [email protected] [email protected]
       sleep 1800
  fi
done

You may do this with a for loop instead of a while:

max_loop=20
for ((count = 0; count < max_loop; count++)); do
  if /home/hadoop/latest/bin/hadoop fs -ls /apps/hdtech/bds/quality-rt/dt=$DATE_YEST_FORMAT2 then
       echo "Files Present" | mailx -s "File Present"  -r [email protected] [email protected]
       break
  else
       echo "Sleeping for half an hour" | mailx -s "Time to Sleep Now"  -r [email protected] [email protected]
       sleep 1800
  fi
done

if [ "$count" -eq "$max_loop" ]; then
  echo "Maximum number of trials reached" >&2
  exit 1
fi

Try this:

counter=0
while true; do
  if /home/hadoop/latest/bin/hadoop fs -ls /apps/hdtech/bds/quality-rt/dt=$DATE_YEST_FORMAT2 then
       echo "Files Present" | mailx -s "File Present"  -r [email protected] [email protected]
       break
  elif [[ "$counter" -gt 20 ]]; then
       echo "Counter limit reached, exit script."
       exit 1
  else
       let counter++
       echo "Sleeping for another half an hour" | mailx -s "Time to Sleep Now"  -r [email protected] [email protected]
       sleep 1800
  fi
done

Explanation

• break - if files are present, it will break and allow the script to process the files.
• [[ "$counter" -gt 20 ]] - if the counter variable is greater than 20, the script will exit.
• let counter++ - increments the counter by 1 at each pass.