Common Log Format

The Common Log Format, also known as the NCSA Common log format, (after NCSA_HTTPd) is a standardized text file format used by web servers when generating server log files. Because the format is standardized, the files can be readily analyzed by a variety of web analysis programs, for example Webalizer and Analog.

Each line in a file stored in the Common Log Format has the following syntax:

host ident authuser date request status bytes

The format is extended by the Combined Log Format with referrer and user-agent fields.

Example

127.0.0.1 user-identifier frank [10/Oct/2000:13:55:36 -0700] "GET /apache_pb.gif HTTP/1.0" 200 2326

A "-" in a field indicates missing data.

• 127.0.0.1 is the IP address of the client (remote host) which made the request to the server.
• user-identifier is the RFC 1413 identity of the client. Usually "-".
• frank is the userid of the person requesting the document. Usually "-" unless .htaccess has requested authentication.
• [10/Oct/2000:13:55:36 -0700] is the date, time, and time zone that the request was received, by default in strftime format %d/%b/%Y:%H:%M:%S %z.
• "GET /apache_pb.gif HTTP/1.0" is the request line from the client. The method GET, /apache_pb.gif the resource requested, and HTTP/1.0 the HTTP protocol.
• 200 is the HTTP status code returned to the client. 2xx is a successful response, 3xx a redirection, 4xx a client error, and 5xx a server error.
• 2326 is the size of the object returned to the client, measured in bytes.

Usage

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See also

• Extended Log Format
• Log management and intelligence
• Web log analysis software
• Web counter
• Data logging
• Syslog

External links

• "Logging Control In W3C httpd: The Common Logfile Format". W3C. July 1995. Retrieved 2013-05-07.

• "Common Logfile Format". Apache webserver. 2013. Retrieved 2013-05-07.

• "Extended Log File Format". W3C Working Draft WD-logfile-960323. W3C. 1996-03-23. Retrieved 2013-05-07.