mjhjmtu

I have a program that throws a segmentation fault on certain circumstances. I want to execute a command when the segmentation fault occurs to process the data, then execute the command again, and keep doing so until the segmentation fault stops.

As a rough attempt at pseudo code,

dodgy_command

while SegFault
 dataProcessing
 dodgy_command
end

I think I need to be using a Trap command, but I don't understand the syntax for this command.

When a program aborts abnormally the exit code (as seen by the shell) typically has the high bit set so the value is 128 or higher. So a simple solution might be

dodgy_command

while [ $? -ge 128 ]
do
 process_data
 dodgy_command
done

If you specifically only want a segfault and not any other type of error, the while line becomes $? -eq 139 (because SEGV is signal 11; 128+11=139).

If you don't get an high valued exit code on failure then it probably means the application is trapping the error, itself, and forcing a different exit code.

You don't mention what language you need to do this in. So, I'm assuming shell script.

You are correct, you want to use a trap. The trap in bash takes a string to execute when a signal is received. I tend to make it a function call so I can clearly define what I want done when I trap the signal.

Here is a sample script.

#!/bin/bash

# define the function that will handle the trap
sigSegFault() echo "Inside sigSegFault"; 

# Trap the Segmentation Violation (signal 11) signal
trap sigSegFault SEGV

# Start infinite loop 
while [[ true ]]; do
 sleep 10
done

exit 0

Simplistic, but contains the basics of what you are asking for.