Best way to know if SIGUSR1 was sent to a process

Question

I am coding in c and wanted to know via coding what's the best way to know if a signal (for example SIGUSR1) terminated a process. Is there a way to make it with a function and flag it so other processes may know it?

More info: The process is a program I did in C. Later when the process ends (with the signal or not) I wanted another program I have to know it. They are connected via fifos.

Answer 1

In the parent process, you can use the wait() system call's WIFSIGNALED(status) macro to check if the child process was terminated by a signal.

Also you can get the signal number using WTERMSIG(status) macro.

Here's a code to demonstrate the idea.

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/wait.h>

int main()
{
    pid_t n = fork();
    if(n==0)
    {
        execvp(/*Some program here for child*/);
    }

    //parent does something

    //Parent waits for child to exit.
    int status;
    pid_t childpid = wait(&status);

    if(WIFSIGNALED(status))
        printf("Parent: My child was exited by the signal number %d\n",WTERMSIG(status));
    else
        printf("Parent: My child exited normally\n"):

    return 0;
}

You can read more about it in the manual: man 2 wait