accesslog: Added logfile locking.

[ashd.git] / doc / accesslog.doc

accesslog(1)
============

NAME
----
accesslog - Access logger for ashd(7)

SYNOPSIS
--------
*accesslog* [*-hFaL*] [*-f* 'FORMAT'] [*-p* 'PIDFILE'] 'OUTFILE' 'CHILD' ['ARGS'...]
*accesslog* *-P* 'LOGFILE'

DESCRIPTION
-----------

The *accesslog* handler starts a single child handler which it passes
all requests it receives, but also logs information about every such
request to 'OUTFILE'. As for the format of the log records, see the
FORMAT section, below.

*accesslog* is a persistent handler, as defined in *ashd*(7), and the
specified child handler must also be a persistent handler.

If 'OUTFILE' is `-`, log records will be written on standard
output. Otherwise, the specified filename is opened in append mode and
kept open for as long as *accesslog* runs. SIGHUP can be sent to
*accesslog* in order to get it to reopen the log file, which can be
useful e.g. for log rotation.

If the child handler exits, *accesslog* exits as well.

Normally, *accesslog* locks the logfile using *fcntl*(2) to ensure
that only one process writes to a logfile at any time. The *-L* switch
can be used to override that behavior to let several processes share a
logfile, or to use logfiles that cannot be locked for some reason.

OPTIONS
-------

*-h*::

	Print a brief help message to standard output and exit.

*-F*::

	Do not flush the log file buffers for each log record. (This
	refers to the internal buffers, not the filesystem buffers.)

*-f* 'FORMAT'::

	Use the specified 'FORMAT' string instead of the default log
	record format. See the FORMAT section, below, for a
	description of the 'FORMAT' string.

*-p* 'PIDFILE'::

	Write the PID of the *accesslog* to 'PIDFILE'. 'PIDFILE' may
	be `-`, in which case the string "`.pid`" is appended to the
	log file name and used instead.

*-a*::

	Try to emulate the Apache "combined" log format as closely as
	possible. Currently, the remote user, identd user, status code
	and number of sent bytes in Apache's combined format are
	replaced with dashes. Effectively, the following format string
	is used:

--------
%A - - [%{%d/%b/%Y:%H:%M:%S %z}t] "%m %u %v" - - "%R" "%G"
--------

*-L*::

	Do not attempt to lock the logfile. Note that this switch
	conflicts with the use of the *-P* option.

*-P* 'LOGFILE'::

	Makes *accesslog* fetch the PID of the process currently
	holding the lock on 'LOGFILE', write that to standard output,
	and then exit. No further command-line arguments are
	processed. This option is useful for sending SIGHUP to
	accesslog when rotating logfiles without having to use a PID
	file.

FORMAT
------

The log record format is specified with the *-f* option described
above. The format string is used as a template and certain fields are
expanded. Characters in the format string not matching such fields are
output as they are. A field is specified as a percent sign, followed
by an optional argument enclosed in braces, followed by a single
character specifying the item to log.

By default, the following format string is used:

--------
%{%Y-%m-%d %H:%M:%S}t %m %u %A "%G"
--------

The following log items are currently specified:

*%{*'HEADER'*}h*::

	Expands into the HTTP header named by 'HEADER'. If the
	specified header does not exist in the request, *%h* expands
	into a dash.

*%u*::

	Expands into the entire raw URL part of the request.

*%U*::

	Expands into the raw URL part of the request, with any query
	string removed if present.

*%m*::

	Expands into the HTTP method.

*%v*::

	Expands into the HTTP version string.

*%r*::

	Expands into the current rest string.

*%t*::

	Expands into the current time, in RFC822 format, unless there
	is an argument present, in which case the argument is used as
	a format string to *strftime*(3). The time is expressed in the
	local timezone.

*%T*::

	As for *%t*, but UTC time is used instead.

*%s*::

	Expands into the non-integral fraction of the second of the
	current time, expressed in microseconds and padded with zeroes
	to 6 digits. For example, *%{%H:%M:%S}t.%s* can be used to log
	fractional time.

*%A*::

	Expands into the `X-Ash-Address` header.

*%H*::

	Expands into the `Host` header.

*%R*::

	Expands into the `Referer` header.

*%G*::

	Expands into the `User-Agent` header.

In any expanded field, any "unsafe" characters are escaped. Currently,
this means that double-quotes and backslashes are prepended with a
backslash, newlines and tabs are expressed as, respectively, `\n` and
`\t`, and any other byte less than 32 or greater than 127 is expressed
as `\xAA`, where `AA` is the hexadecimal representation of the byte.

SIGNALS
-------

SIGHUP::

	Reopen the log file by name. If the log file name cannot be
	re-opened, the old log file stream continues in use.

AUTHOR
------
Fredrik Tolf <fredrik@dolda2000.com>

SEE ALSO
--------
*ashd*(7)