Apache Reference: mod_log_agent, AgentLog
Log File for HTTP User-Agent Header Fields (Deprecated)
Syntax: AgentLog A
Example: AgentLog logs/agent.log
Since: Apache 1.0
This directive specifies the file to which the server
will log the HTTP User-Agent header field of incoming
requests. It has been deprecated, however, and you should use
the CustomLog directive with the ``%{User-Agent}i'' format
string instead.