What is a Log File?

A web server log file is a plain text file. The entries in it are one line apiece, with each entry corresponding to the access of one of your pages by a visitor's browser. The format of the entries in the file is different, depending both on the web server software you use, and the server's configuration.

Here are a couple of log entries from my current log file, which was created by the Apache web server that my hosting service uses. The entry lines are too long to fit nicely in this page, so I've broken each one up over several lines:

The information given in each of the lines is:

• The Internet address of the reader's computer: 219-88-44-141.dialup.xtra.co.nz
• The date and time the request was recieved: [01/Nov/2004:00:04:15 -0800]
• The HTTP request made: "GET /tips/getting-started/article.css HTTP/1.1"
• The HTTP status code: 304
• The number of bytes transferred: - in the first line, 77223 in the second
• The URL of the referring page: "http://www.goingware.com/tips/getting-started/byteorder.html"
• The name of the browser: "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1) Opera 7.23 [en]"

The Internet address may be given is a numerical IP address or as a domain name. This depends on the configuration of your server; either it may not have been able to resolve the domain name, or the server might be configured for performance reasons to not look up the domain name.

The HTTP GET request is used to fetch a whole file. The filename is taken from the document's URL with the protocol (http:) and domain name (//www.goingware.com) stripped off. In the first line, the GET is requesting a CSS stylesheet located at http://www.goingware.com/tips/getting-started/article.css.

The 304 status code in the first log entry indicates that article.css has not been modified since it was last fetched by the client browser. No file data is sent with a 304 response, so the number of file bytes transferred is given as "-". The second log entry has a status code of 200, meaning "OK"; the entire file at the requested location is transferred, with the number of bytes given being the size of the file.