tailfd

tailfd

Tails a file. it should work great. it will continue to work even if a file is unlinked rotated or truncated. It is also ok if the path doesnt exist before watching it

Example

var tail = require('tailfd').tail,
watcher = tail('/some.log',function(line,tailInfo){
  //default line listener. optional.
  console.log('line of data> ',line);
});

when you are done

watcher.close();

install

npm install tailfd

argument structure

tailfd.tail(filename, [options], listener)

• filename

  • this should be a regular file or non existent. the behavior is undefined in the case of a directory.

• options. supported custom options are

  {
  
  "start":undefined, //defaults to the first reported stat.size
  //optional. a hard start position in the file for tail to start emitting data events.
  
  "offset":0,
  //optional.  offset is negtively applied to the start position
  
  "delimiter":"\n"
  //optional. defaults to newline but can be anything
  
  }
  
  // the options object is passed to watchfd as well. With watchfd you may configure
  
  {
  
  "timeout": 60*60*1000, //defaults to one hour
  //how long an inactive file descriptor can remain inactive before being cleared
  
  "timeoutInterval":60*5*1000 //every five minutes
  // how often to check for inactive file descriptors
  
  }
  
  //the options object is also passed directly to fs.watch and fs.watchFile so you may configure
  
  {
  "persistent":true, //defaults to true
  //persistent indicates whether the process should continue to run as long as files are being watched
  
  "interval":0, //defaults 0
  //interval indicates how often the target should be polled, in milliseconds. (On Linux systems with inotify, interval is ignored.) 
  }
  

• callback

  • this is bound to the line event of the watcher. its optional.

    callback(line,tailInfo)
    

  cur and prev are instances of fs.Stats

events

• line String line, Object tailInfo
• data Buffer buffer, Object tailInfo

events inherited from watchfd

• change
  • fs.Stats cur, fs.Stats prev
• open
  • fs.Stats cur,{fd:file descriptor,stat:fs.Stats cur}
• unlink
  • fs.Stats cur,{fd:file descriptor,stat:fs.Stats cur}
• timeout
  • fs.Stats cur,{fd:file descriptor,stat:fs.Stats cur}

tailInfo properties

• stat
  • instanceof fs.Stats
• pos
  • current seek position in the file
• fd
  • file descriptor being tailed
• buf
  • string containing the last data fragment from delimiter parsing

watch file and watch may behave differently on different systems here is the doc for it.

• http://nodejs.org/api/fs.html#fs_fs_writefile_filename_data_encoding_callback
• http://nodejs.org/api/fs.html#fs_fs_watch_filename_options_listener