ICAP log files record ICAP transaction summaries, one line per
	transaction.

	The icap_log option format is:
	icap_log <filepath> [<logformat name> [acl acl ...]]
	icap_log none [acl acl ...]]
	
	Please see access_log option documentation for details. The two
	kinds of logs share the overall configuration approach and many
	features.

	ICAP processing of a single HTTP message or transaction may
	require multiple ICAP transactions.  In such cases, multiple
	ICAP transaction log lines will correspond to a single access
	log line.

	ICAP log uses logformat codes that make sense for an ICAP
	transaction. Header-related codes are applied to the HTTP header
	embedded in an ICAP server response, with the following caveats:
	For REQMOD, there is no HTTP response header unless the ICAP
	server performed request satisfaction. For RESPMOD, the HTTP
	request header is the header sent to the ICAP server. For
	OPTIONS, there are no HTTP headers.

	The following format codes are also available for ICAP logs:

		icap::<A	ICAP server IP address. Similar to <A.

		icap::<service_name	ICAP service name from the icap_service
				option in Squid configuration file.

		icap::ru	ICAP Request-URI. Similar to ru.

		icap::rm	ICAP request method (REQMOD, RESPMOD, or 
				OPTIONS). Similar to existing rm.

		icap::>st	Bytes sent to the ICAP server (TCP payload
				only; i.e., what Squid writes to the socket).

		icap::<st	Bytes received from the ICAP server (TCP
				payload only; i.e., what Squid reads from
				the socket).

		icap::tr 	Transaction response time (in
				milliseconds).  The timer starts when
				the ICAP transaction is created and
				stops when the transaction is completed.
				Similar to tr.

		icap::tio	Transaction I/O time (in milliseconds). The
				timer starts when the first ICAP request
				byte is scheduled for sending. The timers
				stops when the last byte of the ICAP response
				is received.

		icap::to 	Transaction outcome: ICAP_ERR* for all
				transaction errors, ICAP_OPT for OPTION
				transactions, ICAP_ECHO for 204
				responses, ICAP_MOD for message
				modification, and ICAP_SAT for request
				satisfaction. Similar to Ss.

		icap::Hs	ICAP response status code. Similar to Hs.

		icap::>h	ICAP request header(s). Similar to >h.

		icap::<h	ICAP response header(s). Similar to <h.

	The default ICAP log format, which can be used without an explicit
	definition, is called icap_squid:

logformat icap_squid %ts.%03tu %6icap::tr %>a %icap::to/%03icap::Hs %icap::<size %icap::rm %icap::ru% %un -/%icap::<A -

	See also: logformat, log_icap, and %icap::<last_h