text: // Copyright (c) 2003-2011 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  //
  // Distributed under the Boost Software License, Version 1.0. (See accompanying
  // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  
  #include "daemonizer/posix_fork.h"
  #include "misc_log_ex.h"
  
  #include <cstdlib>
  #include <fcntl.h>
  #include <unistd.h>
  #include <stdexcept>
  #include <string>
  #include <sys/stat.h>
  
  namespace posix {
  
  namespace {
    void quit(std::string const & message)
    {
      LOG_ERROR(message);
      throw std::runtime_error(message);
    }
  }
  
  void fork()
  {
    // Fork the process and have the parent exit. If the process was started
    // from a shell, this returns control to the user. Forking a new process is
    // also a prerequisite for the subsequent call to setsid().
    if (pid_t pid = ::fork())
    {
      if (pid > 0)
      {
        // We're in the parent process and need to exit.
        //
        // When the exit() function is used, the program terminates without
        // invoking local variables' destructors. Only global variables are
        // destroyed.
        exit(0);
      }
      else
      {
        quit("First fork failed");
      }
    }
  
    // Make the process a new session leader. This detaches it from the
    // terminal.
    setsid();
  
    // A second fork ensures the process cannot acquire a controlling terminal.
    if (pid_t pid = ::fork())
    {
      if (pid > 0)
      {
        exit(0);
      }
      else
      {
        quit("Second fork failed");
      }
    }
  
    // Close the standard streams. This decouples the daemon from the terminal
    // that started it.
    close(0);
    close(1);
    close(2);
  
    // We don't want the daemon to have any standard input.
    if (open("/dev/null", O_RDONLY) < 0)
    {
      quit("Unable to open /dev/null");
    }
  
    // Send standard output to a log file.
    const char* output = "/tmp/bitchavezcoin.daemon.stdout.stderr";
    const int flags = O_WRONLY | O_CREAT | O_APPEND;
    const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
    if (open(output, flags, mode) < 0)
    {
      quit("Unable to open output file: " + std::string(output));
    }
  
    // Also send standard error to the same log file.
    if (dup(1) < 0)
    {
      quit("Unable to dup output descriptor");
    }
  }
  
  } // namespace posix
  