openmpi/opal/util/daemon_init.c

/*
 * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
 *                         University Research and Technology
 *                         Corporation.  All rights reserved.
 * Copyright (c) 2004-2005 The University of Tennessee and The University
 *                         of Tennessee Research Foundation.  All rights
 *                         reserved.
 * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart, 
 *                         University of Stuttgart.  All rights reserved.
 * Copyright (c) 2004-2005 The Regents of the University of California.
 *                         All rights reserved.
 * $COPYRIGHT$
 * 
 * Additional copyrights may follow
 * 
 * $HEADER$
 */


#include "opal_config.h"
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#include <sys/stat.h>
#include <fcntl.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <stdlib.h>

#include "opal/util/daemon_init.h"
#include "opal/constants.h"


int opal_daemon_init(char *working_dir)
{
#if defined(HAVE_FORK)
#ifndef __WINDOWS__
    /* it seems that there is an entirely different way to write daemons in 
       WINDOWS land. Firstly, they are called services and the way to 
       go about it is to get a service handle annd then call CreateService()
       So, I am guessing that this piece of code is called only by UNIX versions */

    pid_t pid;
    int fd;

    if ((pid = fork()) < 0) {
        return OPAL_ERROR;
    } else if (pid != 0) {
        exit(0);   /* parent goes bye-bye */
    }
    
    /* child continues */
#if defined(HAVE_SETSID)
    setsid();  /* become session leader */
#endif

    if (NULL != working_dir) {
        chdir(working_dir);  /* change working directory */
    }

    /* connect input to /dev/null */
    fd = open("/dev/null", O_RDONLY);
    if(fd > STDIN_FILENO) {
        dup2(fd, STDIN_FILENO);
        close(fd);
    }

    /* connect outputs to /dev/null */
    fd = open("/dev/null", O_RDWR|O_CREAT|O_TRUNC, 0666);
    if (fd >= 0) {
        dup2(fd, STDOUT_FILENO);
        dup2(fd, STDERR_FILENO);
        /* just to be safe, make sure we aren't trying
         * to close stdout or stderr! since we dup'd both
         * of them to the same fd, we can't just close it
         * since one of the two would still be open and
         * someone could attempt to use it.
         */
        if(fd != STDOUT_FILENO && fd != STDERR_FILENO) {
           close(fd);
        }
    } else {
        return OPAL_ERR_FATAL;
    }

    return OPAL_SUCCESS;
#else
    printf ("This function has not been implemented in windows yet, file %s line %d\n", __FILE__, __LINE__);
    abort();
#endif

#else /* HAVE_FORK */
    return OPAL_ERR_NOT_SUPPORTED;
#endif
}