Lightweight logging for NodeJS. Includes a streaming log reader.

$ npm install log

By default, a Log’s stream is stdout, and its log level defaults is DEBUG.

Instead of DEBUG, let’s create a log with the info level:

var Log = require('log')
  , log = new Log('info');
log.debug('preparing email');
log.info('sending email');
log.error('failed to send email');

Specifying a specific stream:

var fs = require('fs')
 , Log = require('log')
 , log = new Log('debug', fs.createWriteStream('my.log'));

Instead of the log level constants, you can just supply a string:

var Log = require('log')
  , log = new Log('warning');

You can use %s to pass arguments (much like console.log()):

log.error('oh no, failed to send mail to %s.', user.email);

To stream a log, simply pass a readable stream instead of a writable:

var Log    = require('log')
  , fs     = require('fs')
  , stream = fs.createReadStream(__dirname + '/file.log')
  , log    = new Log('debug', stream);
log.on('line', function(line){
  console.log(line);
});

(Note: log.js assumes utf8 encoded data.)

Example output:

{ date: Sun, 26 Sep 2010 01:26:14 GMT
, level: 1
, levelString: 'ALERT'
, msg: 'a alert message'
}
{ date: Sun, 26 Sep 2010 01:26:14 GMT
, level: 0
, levelString: 'EMERGENCY'
, msg: 'a emergency message'
}

Mirror that of syslog:

• 0 EMERGENCY system unusable
• 1 ALERT immediate action required
• 2 CRITICAL condition critical
• 3 ERROR condition error
• 4 WARNING condition warning
• 5 NOTICE condition normal, but significant
• 6 INFO a purely informational message
• 7 DEBUG debugging information

(The MIT License)

Copyright (c) 2009-2010 TJ Holowaychuk <tj@vision-media.ca>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.