Interrupt command line execution in Fortran without killing main program

Question

I have a Fortran program that runs a series of identical calculations on a number of different input data. After doing these calculations the code then always writes a GNUplot script that does some diagnostic plotting (nothing too difficult) and runs it using execute_command_line in Linux.

This usually works well, but after some time I think there must be a memory leak of some kind that works cumulative, because the GNUplotting becomes slower and slower. At some point it virtually stalls.

My question is therefore: Is it possible to interrupt the call to execute_command_line using the keyboard without killing the main Fortran program? Needless to say, CTRL-C kills everything, which is not what I want: I want the main program to continue.

I have been playing with the optional flag wait=.true. but this does not help.

Also, I know that the memory leak has to be fixed (or whatever the cause is), but for now I would like to first see the diagnostic output.

pause statement...? http://docs.oracle.com/cd/E19957-01/805-4939/6j4m0vnal/index.html — roygvib, Jun 29 '15 at 14:29
See http://stackoverflow.com/questions/26540044/how-do-you-kill-all-child-processes-without-killing-the-parent You must trap the signals in the main program. — Vladimir F Героям слава, Jun 29 '15 at 14:32
I would prefer a C extension instead, see https://airtower.wordpress.com/2010/06/16/catch-sigterm-exit-gracefully/ — Vladimir F Героям слава, Jun 29 '15 at 14:55
I created an example, but I cannot test it, because in my shell it does not terminate the main program at all? Which OS and shell do you use? — Vladimir F Героям слава, Jun 29 '15 at 16:45
Sorry Vladimir, I hadn't seen your previous comment. I am using ubuntu 14.04 LTS. I compile using gfortran (with C preprocessiong). The F program is run using mpirun. Do you need more information? — Toon, Jun 29 '15 at 17:22
It is better to put the solution in an answer, even if it is just a workaround. — Vladimir F Героям слава, Jul 03 '15 at 14:23

score 0 · Accepted Answer · edited May 23 '17 at 12:30

The only solution I have been able to come up with is kind of a workaround:

Modify the shell script so that it
- runs the Fortran program in the background: ./mpirun prog_name options &
- gets the PID of this proces: proc_PID=$!
- waits for the process: wait $proc_PID
- traps an interrupt signal: trap handler SIGINT
- lets the handler send a SIGURS1 signal: function handler() { kill -SIGUSR1 $proc_PID }
modify the Fortran code so that it catches the SIGUSR1 signal and does what you want with it. For example by having a look here.

By running the mpi process in the background you avoid killing mpirun with SIGINT, which cannot be trapped but you send instead a SIGURS1, which is properly propagated to the mpi processes where it can be handled with directly.

As a side note, however, I realized that this will not solve my problem as my problem was related to an external call to gnuplot using execute_command_line. Since I had a cumulative memory leak, at some point this call started taking for ever because memory resources became scarcer. So the only thing I could have done is manually killing the gnuplot process.

Better, of course, was fixing the memory leak, which I did.

Interrupt command line execution in Fortran without killing main program

1 Answers1