Linux 判断进程是否已经运行的程序

   bool
   ServerProcess::isAlreadyRunning()
   {
   #ifndef __linux__
      WarningLog(<<"can't check if process already running on this platform (not implemented yet)");
      return false;
   #else
      if(mPidFile.size() == )
      {
         // if no PID file specified, we do not make any check
         return false;
      }

      pid_t running_pid;
      std::ifstream _pid(mPidFile.c_str(), std::ios_base::in);
      if(!_pid.good())
      {
         // if the file doesn't exist or can't be opened, just ignore
         return false;
      }
      _pid >> running_pid;
      _pid.close();

      StackLog(<< mPidFile << " contains PID " << running_pid);

      Data ourProc = Data("/proc/self/exe");
      Data otherProc = Data("/proc/") + Data(running_pid) + Data("/exe");
      char our_exe[], other_exe[];
      int buf_size;

      buf_size = readlink(ourProc.c_str(), our_exe, );
      if(buf_size <  || buf_size == )
      {
         // if readlink fails, just ignore
         return false;
      }
      our_exe[buf_size] = ;

      buf_size = readlink(otherProc.c_str(), other_exe, );
      if(buf_size <  || buf_size == )
      {
         // if readlink fails, just ignore
         return false;
      }
      other_exe[buf_size] = ;

      if(strcmp(our_exe, other_exe) == )
      {
         ErrLog(<<"already running PID: " << running_pid);
         return true;
      }
      return false;
   #endif
   }