cdsa/cdsa_utilities/daemon.cpp

   1 /*
   2  * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 //
  20 // demon - support code for writing UNIXoid demons
  21 //
  22 #ifdef __MWERKS__
  23 # define _CPP_DEMON
  24 #endif
  25
  26 #include <Security/daemon.h>
  27 #include <Security/logging.h>
  28 #include <sys/types.h>
  29 #include <errno.h>
  30 #include <unistd.h>
  31 #include <fcntl.h>
  32
  33 namespace Security
  34 {
  35
  36 namespace Daemon
  37 {
  38
  39 //
  40 // Daemonize this process, the UNIX way.
  41 //
  42 bool incarnate()
  43 {
  44         // fork with slight resilience
  45         for (int forkTries = 1; forkTries <= 5; forkTries++) {
  46                 switch (fork()) {
  47                 case 0:                 // child
  48                         // we are the daemon process (Har! Har!)
  49                         break;
  50                 case -1:                // parent: fork failed
  51                         switch (errno) {
  52                         case EAGAIN:
  53                         case ENOMEM:
  54                                 Syslog::warning("fork() short on resources (errno=%d); retrying", errno);
  55                                 sleep(forkTries);
  56                                 continue;
  57                         default:
  58                                 Syslog::error("fork() failed (errno=%d)", errno);
  59                                 return false;
  60                         }
  61                 default:                // parent
  62                         // @@@ we could close an assurance loop here, but we don't (yet?)
  63                         exit(0);
  64                 }
  65         }
  66
  67         // fork succeeded; we are the child; parent is terminating
  68
  69         // create new session (the magic set-me-apart system call)
  70         setsid();
  71
  72         // redirect standard channels to /dev/null
  73         close(0);       // fail silently in case 0 is closed
  74         if (open("/dev/null", O_RDWR, 0) == 0) {        // /dev/null could be missing, I suppose...
  75                 dup2(0, 1);
  76                 dup2(0, 2);
  77         }
  78
  79         // ready to roll
  80         return true;
  81 }
  82
  83
  84 } // end namespace Daemon
  85
  86 } // end namespace Security