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node.js

Why fs.watchFile called twice in Node?

Ubuntu 12.04 Node v0.6.14 CoffeeScript 1.3.1 

fs.watchFile coffee_eval, (e) ->
  console.log e
  result = spawn 'coffee', ['-bc', coffee_eval]
  msg = ''
  result.stderr.on 'data', (str) ->
    msg+= str
  result.stderr.on 'end', ->
    console.log 'msg: ', msg
  print "!! #{coffee_eval}\n"

Whole code on gist: https://gist.github.com/2621576

Every time I save a file which is watched, the main function is called twitce rather than once.
My Editor is Sumlime Text 2.

the output words can be see :
enter image description here

Solution

  • fs.watchFile is unstable. From the node docs:

    fs.watchFile(filename, [options], listener)#

    Stability: 2 - Unstable. Use fs.watch instead, if available.

    You can try fs.watch, but unfortunately it may suffer from the same problem. I had the same issue with fs.watch on windows, when trying to create a similar monitor script.

    The workaround was to log the time when the modification occurs and ignore the second change if it was triggered withing a few milliseconds. A bit ugly but it worked.