How to persistently run your script with Bash

1 minute read


This is a simple script that saves a lot of headaches for me. The situation: I’m running a proprietary software and it seems that there is a problem with the way our license server is setup, because from time to time the process will stop due to “not enough license” even though we have enough. Then we have to rerun, which is ok because there are checkpoint files, but it is a pain to constantly check whether my run has crashed or not.

The solution is simple, and I’m bashing (lol) myself for not writing this ten-liner much earlier. The logic is basically a conditional loop with time delays. We keep trying to rerun every $time_delay and exit the loop if certain condition is satisfied. In my case, the condition is the string All runs succeeded appears in the log file.

This is basically first (and maybe last) time I ever used the until loop. It is just the opposite of while, so it doesn’t get used a lot since you can just negate the condition and use while instead. So this is the main logic:

until grep "All runs succeeded" $log; do
    sleep $time_delay

Then the rest is just cosmetic. I add default $time_delay of 15 mins if none is specified; I avoid time delay for the first loop iteration; I echo some (encouraging) messages to stdout; and finally add a pop-out zenity window once the whole shebang is done.

# usage: ./ input_file log_file [time_delay, def. 15mins]

[ "$3" = "" ] && time_delay="15m" || time_delay=$3

until grep "All runs succeeded" $log; do
    [ $counter -gt 0 ] && sleep $time_delay
    echo "Retry #$counter | time delay is $time_delay"

zenity --info --text "$0 done"

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