mysplit.c

/* 
 * mysplit.c - Shell lab test program
 * 
 * Forking version of the myspin programs. Useful for testing
 * shell code that sends signals to process groups.
 *
 * Usage: ./mysplit [secs]
 */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <string.h>

#include "config.h"

char buf[MAXBUF];

void sigalrm_handler(int signum) 
{
    exit(0);
}

int main(int argc, char **argv) 
{
    int rc;
    int standalone;
    int syncfd;
    char *str;
    char *cmdp;
    struct stat stat;

    signal(SIGALRM, sigalrm_handler);

    if (fork() == 0) { /* child */
	/* 
	 * Determine if the shell is running standalone or under the
	 * control of the driver program. If running under the driver, get
	 * the number of the driver's synchronizing domain socket
	 * descriptor.  
	 */
	standalone = 1;
	if ((str = getenv("SYNCFD")) != NULL) {
	    syncfd = atoi(str);              /* Get descriptor number */
	    if (fstat(syncfd, &stat) != -1)  /* Is is open? */
		standalone = 0;
	}
	
	/* 
	 * If the job is being run by the driver, then synchronize with
	 * the driver over its synchronizing domain socket.  Ignore any
	 * command line argument.  
	 */
	
	if (!standalone) {
	    alarm(JOB_TIMEOUT);
	    cmdp = "";
	    if ((rc = send(syncfd, cmdp, strlen(cmdp), 0)) < 0) {
		perror("send");
		exit(1);
	    }
	    
	    if ((rc = recv(syncfd, buf, MAXBUF, 0)) < 0) {
		perror("recv");
		exit(1);
	    }
	    exit(0);
	}
	
	/*
	 * Otherwise spin until timing out 
	 */
	else {
	    if (argc > 1)
		alarm(atoi(argv[1]));
	    else
		alarm(JOB_TIMEOUT);
	    
	    while(1);
	}
	
    }

    /* Parent waits for child to terminate */
    alarm(JOB_TIMEOUT);
    wait(NULL);
    exit(0);
}