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/*---------------------------------------------------------------------------*\
NAME
daemon.c - replacement daemon(3) function
DESCRIPTION
This source file contains a version of a BSD-style daemon(3)
function, a function to "daemonize" the calling process. This
implementation is based both on the generic daemon logic defined in
the Unix Programmer's FAQ and on the daemon_start() function in
W. Richard Stevens' _Unix_Network_Programming_ book (Prentice-Hall,
1990). At the time of this writing, the Unix Programmer's FAQ is
located at `http://www.whitefang.com/unix/faq_toc.html' (among
other places).
LICENSE
This source code is released under a BSD-style. See the LICENSE
file for details.
Copyright (c) 2003-2015 Brian M. Clapper, bmc@clapper.org
\*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*\
Includes
\*---------------------------------------------------------------------------*/
#include <stdio.h>
#include <stdlib.h>
#include <syslog.h>
#include <errno.h>
#include <string.h>
#include <assert.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include "config.h"
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif /* HAVE_SYS_FILE_H */
/*---------------------------------------------------------------------------*\
Static Routines
\*---------------------------------------------------------------------------*/
/* redirect_fds(): redirect stdin, stdout, and stderr to /dev/NULL */
static void redirect_fds()
{
(void) close(0);
(void) close(1);
(void) close(2);
if (open("/dev/null", O_RDWR) != 0)
{
syslog(LOG_ERR, "Unable to open /dev/null: %s", strerror(errno));
exit(1);
}
(void) dup(0);
(void) dup(0);
}
static int do_fork(void)
{
int status = 0;
switch(fork())
{
case 0:
/* This is the child that will become the daemon. */
break;
case -1:
/* Fork failure. */
status = -1;
break;
default:
/* Parent: Exit. */
_exit(0);
}
return status;
}
/*---------------------------------------------------------------------------*\
Public Routines
\*---------------------------------------------------------------------------*/
int daemon(int nochdir, int noclose)
{
int status = 0;
openlog("daemonize", LOG_PID, LOG_DAEMON);
/* Fork once to go into the background. */
if((status = do_fork()) < 0 )
;
/* Create new session */
else if(setsid() < 0) /* shouldn't fail */
status = -1;
/* Fork again to ensure that daemon never reacquires a control terminal. */
else if((status = do_fork()) < 0 )
;
else
{
/* clear any inherited umask(2) value */
umask(0);
/* We're there. */
if(! nochdir)
{
/* Go to a neutral corner. */
chdir("/");
}
if(! noclose)
redirect_fds();
}
return status;
}
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