如何在node.js中杀死生成的进程

Question

I have a function that needs to kill the previous ffmpeg process before spawning a new one however I'm not sure how to do this because I will understandably get ffmpeg is not defined if I attempt the code below:

var ffmpeg_started = false;
function start_ffmpeg(file) {
  if (ffmpeg_started)
    ffmpeg.kill();
  var command =  [
               '-i', file,
               '-f', 'mpegts',
               '-codec:v', 'mpeg1video',
               'http://server.com/'
                ];
  }
  const ffmpeg = spawn('ffmpeg', command);  
  ffmpeg_started = true;
}

Answer 1

An easy/simple solution is to just move the ffmpeg declaration into the parent scope. Then you could do away with the boolean flag and just check ffmpeg 's value to tell if it's still running. For example:

var ffmpeg;
function start_ffmpeg(file) {
  if (ffmpeg)
    ffmpeg.kill();
  ffmpeg = spawn('ffmpeg', ...);
}

If you need to anything more complex than that, you might consider using a queue or similar to handle invocations of ffmpeg more elegantly.