SIGINT wrapper for lighttpd graceful restart feature under runit.

sigint.c

/* SIGINT.c */

/* Errors */
#define RC_TARGET               13
#define RC_SIGNAL_HANDLER       15
#define RC_EXEC                 23
#define RC_BAD_OPTION           24

/* INC */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include <signal.h>


/* Child PID */
int pid;

/* sighandler */
void sigHandler(int signal) {
    /* Not forked yet */
    if (!pid)
	return;

    switch (signal) {
	case SIGHUP:
	case SIGUSR1:
	case SIGUSR2:
	    /* Forward to child */
	    kill(pid, signal);
	    break;
	    
	case SIGINT:
	    /* Forward signal and we exit */
	    kill(pid, SIGINT);
	    _exit(0);

	case SIGTERM:
	    /* Transform to graceful stop */
	    kill(pid, SIGINT);
	    break;
  
	case SIGQUIT:
	    /* Mapped to SIGTERM */
	    kill(pid, SIGTERM);
	    break;
	    
	/* No SIGKILL. We could map some other signal to sigkill, but it seems pointless. */
    }
}

void checkSignal(void *res) {
    if (res == SIG_ERR) {
    	fprintf( stderr, "Error setting up signal handler" );
	    exit( RC_SIGNAL_HANDLER );
    }
}

int main(int argc, char* argv[], char* envp[]) {
  /* Command line args */
  if (argc < 2) {
    fprintf(stderr, "Usage:\t%s target [options]\n", argv[0]);
    return(-1);
  }

  char* target = argv[1];
  
  /* Install the signal handler */
  checkSignal(signal(SIGHUP,  sigHandler));
  checkSignal(signal(SIGINT,  sigHandler));
  checkSignal(signal(SIGQUIT, sigHandler));
  checkSignal(signal(SIGTERM, sigHandler));
  checkSignal(signal(SIGUSR1, sigHandler));
  checkSignal(signal(SIGUSR2, sigHandler));
  checkSignal(signal(SIGPIPE, SIG_IGN));
  checkSignal(signal(SIGALRM, SIG_IGN));

  /* Fork */
  if (!(pid = fork()))   {
    /* execute */
    execve(target, & argv[1], envp);
    fprintf(stderr, "Error executing target: %s", target);
    return RC_EXEC;
  }

  /* Wait for the child to exit then return. (Or we exit from signal handler.) */
  int status;
  wait(&status);
  return status;
}