Terminating a c function

Question

I want to make a function in c, that will capture video under Linux. I embedded ffmpeg command via system() in my c program, which captures video. ffmpeg terminates by pressing [q]. How can I include termination into my c program.

This function is part of a server.c program. When client requests for termination, I want video cature function to terminate. Is this possible?

#include<stdio.h>
#include <string.h>


main()
{

char command[180];

sprintf(command, "ffmpeg -f v4l2 -r 25 -s 640x480 -i /dev/video0 out.avi");
system(command);

}

Answer 1

As you asked sample for fork, exec, kill here is possible solution. avconv is replacement for ffmpeg on my pc.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>
#include <errno.h>
#include <assert.h>
#include <unistd.h>
#include <sched.h>
#include <sys/wait.h>

pid_t parent_pid;

void sigquit_handler (int sig)
{
    assert(sig == SIGKILL);
    pid_t self = getpid();
    if (parent_pid != self)
    {
        printf("recording done");
        _exit(0);
    }
}

int main()
{
    int pid = 0;
    int status;
    pid_t child;

    signal(SIGKILL, sigquit_handler);
    parent_pid = getpid();

    pid = fork();

    if ( pid == 0)
    {
        execl("/usr/bin/avconv","avconv","-f","video4linux2","-r","25","-s","640x480","-i","/dev/video0","out.avi",(char*)0);
    }
    else if( pid > 0)
    {
        sleep(5);
        kill(pid, SIGKILL);

        child = wait(&status);
        printf("child %d succesully quit\n", (int)child);
    }
    return 0;
}