SysAdmin's Journey

Estimate Time-to-completion With

Like many of you other sysadmins, I run a lot of ad-hoc, long running jobs. Also like many of you, I have a full plate and can’t stand to sit around watching things run. Often times, I will start such a job and forget to come back to it until the end of the day. I needed a way to find out quickly about how long these tasks would take to run so that I could make a mental note or set a reminder to check the task later. Over time, I noticed that the vast majority of the jobs I ran could be quantified and estimated by coming up with custom shell pipeline. For instance, I need to iterate over something, and write output to a file. I know that I’ll be close to being done when I hit 100,000 lines in that file. If the file was named output.log, then I could monitor progress by running ‘wc -l output.log’.

These conditions gave birth to - a shell script that runs a command that you specify once every 30 seconds. The command needs to give back an integer. You can optionally specify an end integer, and it will (fairly accurately) give you back an estimated completion time. takes two arguments, one required, the other optional. The first argument is the command that generates an integer. The second argument is optional, it’s the end integer that will allow the script to estimate time remaining. Perhaps the script is best explained by giving a full example. Open up a terminal, and issue the following at the command line:

echo "" > test.out; for i in `seq 1 600`; do echo "SUCCESS" >> test.out; echo "$i" >> test.out; sleep 3; done

This is a one-liner script that echoes two log lines to a file once every 3 seconds for 30 minutes. Before hitting the enter key, open up another terminal, and run this in it:

./ 'grep -c SUCCESS test.out' 600

It takes an iteration or two to get enough data to make a good estimate, but you should start seeing output like this:

Current=.13/sec TotalAvg=.13/sec Total=4/600 0% 1.27 hrs left
Current=.33/sec TotalAvg=.23/sec Total=14/600 2.00% 42.46 mins left
Current=.33/sec TotalAvg=.26/sec Total=24/600 4.00% 36.92 mins left
Current=.33/sec TotalAvg=.28/sec Total=34/600 5.00% 33.69 mins left
Current=.33/sec TotalAvg=.29/sec Total=44/600 7.00% 31.95 mins left
Current=.33/sec TotalAvg=.29/sec Total=54/600 9.00% 31.37 mins left
Current=.33/sec TotalAvg=.30/sec Total=64/600 10.00% 29.77 mins left

The first column is the statistics related to average units per second. Let’s examine the last line. Now, executes the command you give it once every thirty seconds. The .33/sec figure means that in the last iteration, the integer incremented .33 units per second. Since we echo the word “SUCCESS” out to the file once every 3 seconds, the math here is sound. The tTotalAvg of .30/sec is the same metric, except instead of being for the last execution, it is the average since the startup of The second column shows the completion status. Again, looking at the last line, we are told that we have 64 units out of our total 600, meaning we’re roughly 10% done. The final column tells us what the script estimates as the time remaining before we are at 100% done.


  • I’m not a math major. This is simple stuff. If you know ‘bc’ and have suggestions, I’d be happy to hear them.
  • Watch your quoting on the first argument. If you’re doing complex pipelines, you will likely need to escape some characters. Check out the quoting section of the bash-scripting howto for tips.
  • Let me know if it works great for you. Let me know if it doesn’t. I’ll try to make it better if I can. I use it all the time and it works well for me.


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