custom file logging stream

Author: polotek

file-logger-example.js

@@ -0,0 +1,15 @@
+var Stream = require('stream'),
+    FileLogStream = require('./filelogstream');
+
+var format = function(d) {
+      return 'log: ' + d + '\n';
+    };
+
+var logger = new FileLogStream('./log.txt', { formatLog: format });
+
+var s = new Stream();
+s.pipe(logger);
+s.emit('data', 'message 1');
+s.emit('data', 'message 2');
+s.emit('data', 'message 3');
+s.emit('end');

filelogstream.js

@@ -0,0 +1,38 @@
+var Stream = require('stream'),
+  util = require('util'),
+  fs = require('fs');
+
+var FileLogStream = function(filepath, opts) {
+  opts = opts || {};
+
+  this._fileStream = fs.createWriteStream(filepath, opts);
+  this.readable = true;
+  this.writable = true;
+
+  var fileWrite, formatLog;
+  if(typeof opts.formatLog === 'function') {
+    formatLog = opts.formatLog;
+    fileWrite = this._fileStream.write;
+    this._fileStream.write = function(data) {
+      data = formatLog(data);
+      return fileWrite.call(this, data);
+    };
+  }
+
+  this.on('pipe', function(readStream) {
+    readStream.pipe(this._fileStream);
+  });
+};
+util.inherits(FileLogStream, Stream);
+FileLogStream.prototype.write = function(data) {
+  this.emit('data', data);
+  return true;
+};
+FileLogStream.prototype.end = function(data) {
+  if(data) { this.write(data); }
+
+  this._fileStream.end();
+  this.emit('end');
+};
+
+module.exports = FileLogStream;