How to retry a command in Bash?

Question

I have a command that should take less than 1 minute to execute, but for some reason has an extremely long built-in timeout mechanism. I want some bash that does the following:

success = False

try(my_command)

while(!(success))
wait 1 min
if my command not finished
     retry(my_command)
else
     success = True   
end while

How can I do this in Bash?

Answer 1

Look at the GNU timeout command. This kills the process if it has not completed in a given time; you'd simply wrap a loop around this to wait for the timeout to complete successfully, with delays between retries as appropriate, etc.

while timeout -k 70 60 -- my_command; [ $? = 124 ]
do sleep 2  # Pause before retry
done

If you must do it in pure bash (which is not really feasible - bash uses lots of other commands), then you are in for a world of pain and frustration with signal handlers and all sorts of issues.

---

Please expand on your answer a little. -k 70 is --kill-after= 70 seconds, 124 exit on timeout; what is the 60?

The linked documentation does explain the command; I don't really plan to repeat it all here. The synopsis is timeout [options] duration command [arg]...; one of the options is -k duration. The -k duration says "if the command does not die after the SIGTERM signal is sent at 60 seconds, send a SIGKILL signal at 70 seconds" (and the command should die then). There are a number of documented exit statuses; 124 indicates that the command timed out; 137 that it died after being sent the SIGKILL signal, and so on. You can't tell if the command itself exits with one of the documented statuses.