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() == 0)
     {
        // 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[513], other_exe[513];
     int buf_size;
  
     buf_size = readlink(ourProc.c_str(), our_exe, 512);
     if(buf_size < 0 || buf_size == 512)
     {
        // if readlink fails, just ignore
        return false;
     }
     our_exe[buf_size] = 0;
  
     buf_size = readlink(otherProc.c_str(), other_exe, 512);
     if(buf_size < 0 || buf_size == 512)
     {
        // if readlink fails, just ignore
        return false;
     }
     other_exe[buf_size] = 0;
  
     if(strcmp(our_exe, other_exe) == 0)
     {
        ErrLog(<<"already running PID: " << running_pid);
        return true;
     }
     return false;
  #endif
  }