server/background.c

   1 /* nbdkit
   2  * Copyright Red Hat
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdarg.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40 #include <fcntl.h>
  41
  42 #include "internal.h"
  43
  44 /* True if we forked into the background (used to control log messages). */
  45 bool forked_into_background;
  46
  47 #ifndef WIN32
  48
  49 /* This is a separate function because RHEL 6-era gcc requires pragmas
  50  * outside function scope.
  51  */
  52 #pragma GCC diagnostic push
  53 #pragma GCC diagnostic ignored "-Wunused-result"
  54 static void
  55 chdir_root (void)
  56 {
  57   chdir ("/");
  58 }
  59 #pragma GCC diagnostic pop
  60
  61 /* Run as a background process.  If foreground is set (ie. -f or
  62  * equivalent) then this does nothing.  Otherwise it forks into the
  63  * background and sets forked_into_background.
  64  */
  65 void
  66 fork_into_background (void)
  67 {
  68   pid_t pid;
  69
  70   if (foreground)
  71     return;
  72
  73   pid = fork ();
  74   if (pid == -1) {
  75     perror ("fork");
  76     exit (EXIT_FAILURE);
  77   }
  78
  79   if (pid > 0)                  /* Parent process exits. */
  80     exit (EXIT_SUCCESS);
  81
  82   chdir_root ();
  83
  84   /* By this point, stdin/out have been redirected to /dev/null.
  85    * If not verbose, set stderr to the same as stdout as well.
  86    */
  87   if (!verbose)
  88     dup2 (STDOUT_FILENO, STDERR_FILENO);
  89
  90   forked_into_background = true;
  91   debug ("forked into background (new pid = %d)", getpid ());
  92 }
  93
  94 #else /* WIN32 */
  95
  96 void
  97 fork_into_background (void)
  98 {
  99   if (foreground)
 100     return;
 101
 102   fprintf (stderr, "nbdkit: You must use the -f option on Windows.\n");
 103   NOT_IMPLEMENTED_ON_WINDOWS ("daemonizing");
 104 }
 105
 106 #endif /* WIN32 */