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Andrew Ford
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README

CRONOLOG version 1.6.1

"cronolog" is a simple program that reads log messages from its input
and writes them to a set of output files, the names of which are
constructed using a template and the current date and time.  The
template uses the same format specifiers as the Unix date command
(which are the same as the standard C strftime library function).

"cronolog" is intended to be used in conjunction with a Web server, such
as Apache, to split the access log into daily or monthly logs. For
example the Apache configuration directives:

	TransferLog "|/www/sbin/cronolog /www/logs/%Y/%m/%d/access.log"
	ErrorLog    "|/www/sbin/cronolog /www/logs/%Y/%m/%d/errors.log"

would instruct Apache to pipe its access and error log messages into
separate copies of cronolog, which would create new log files each day
in a directory hierarchy structured by date, i.e. on 31 December 1996
messages would be written to

	/www/logs/1996/12/31/access.log
	/www/logs/1996/12/31/errors.log

after midnight the files

	/www/logs/1997/01/01/access.log
	/www/logs/1997/01/01/errors.log

would be used, with the directories 1997, 1997/01 and 1997/01/01 being
created if they did not already exist.

Each character in the template represents a character in the expanded
filename, except for date and time format specifiers, which are
replaced by their expansion.  Format specifiers consist of a `%'
followed by one of the following characters:

 %	a literal % character
 n	a new-line character
 t	a horizontal tab character

Time fields:

 H 	hour (00..23)
 I 	hour (01..12)
 p 	the locale's AM or PM indicator
 M 	minute (00..59)
 S 	second (00..61, which allows for leap seconds)
 X 	the locale's time representation (e.g.: "15:12:47")
 Z 	time zone (e.g. GMT), or nothing if the time zone cannot be determined

Date fields:

 a 	the locale's abbreviated weekday name (e.g.: Sun..Sat)
 A 	the locale's full weekday name (e.g.: Sunday .. Saturday)
 b 	the locale's abbreviated month name (e.g.: Jan .. Dec)
 B 	the locale's full month name, (e.g.: January .. December)
 c 	the locale's date and time (e.g.: "Sun Dec 15 14:12:47 GMT 1996")
 d 	day of month (01 .. 31)
 j 	day of year (001 .. 366)
 m 	month (01 .. 12)
 U 	week of the year with Sunday as first day of week (00..53, where
	week 1 is the week containing the first Sunday of the year)
 W 	week of the year with Monday as first day of week (00..53, where
	week 1 is the week containing the first Monday of the year)
 w 	day of week (0 .. 6, where 0 corresponds to Sunday)
 x 	locale's date representation (e.g. today in Britain: "15/12/96")
 y 	year without the century (00 .. 99)
 Y 	year with the century (1970 .. 2038)

Other specifiers may be available depending on the C library's
implementation of the strftime function.  Before writing a message
cronolog checks the time to see whether the current log file is still
valid and if not it closes the current file, expands the template
using the current date and time to generate a new file name, opens the
new file (creating missing directories on the path of the new log file
as needed unless the program is compiled with -DDONT_CREATE_SUBDIRS)
and calculates the time at which the new file will become invalid.

The most up-to-date version of "cronolog" can be found at:

	http://www.ford-mason.co.uk/resources/cronolog/


INSTALLATION
============

Cronolog uses GNU autoconf, so it is configured and built
with the standard sequence:

	./configure
	make

To install type "make install" or simply copy the executable
"src/cronolog" to a suitable directory.

Cronolog has a number of options that can be set either by including
in CFLAGS when configuring, or by editing the file "src/config.h":

	-DFILE_MODE=octal-number	mode used for creating files (default is 0664)
	-DDIR_MODE=octal-number		mode used for creating directories (default is 0775)
	-DDONT_CREATE_SUBDIRS		don't include code to create missing directories
	-DNEED_GETOPT_DEFS		if your platform doesn't declare getopt()

e.g. to set the file mode to 0600:

	CFLAGS="-O2 -DFILE_MODE=0600" ./configure


TESTING
=======

The package includes a simple test harness program (cronotest), which
tests out the lower level functions and prints out debugging
information.  The test program is run with the command line:

	cronotest [-d] "template" count

template is the filename template and count is the number of periods
to evaluate, for example:

	$ cronotest "%Y/%m/%d/access.log" 4
	Determining periodicity of "%Y/%m/%d/access.log"
	%Y -> yearly
	%m -> monthly
	%d -> daily
	Rotation period is per day
	Start time is Sun Dec 15 15:55:43 1996 (850665343)
	Period   1 starts at Sun Dec 15 00:00:00 1996 (850608000):  "1996/12/15/access.log"
	Period   2 starts at Mon Dec 16 00:00:00 1996 (850694400):  "1996/12/16/access.log"
	Period   3 starts at Tue Dec 17 00:00:00 1996 (850780800):  "1996/12/17/access.log"
	Period   4 starts at Wed Dec 18 00:00:00 1996 (850867200):  "1996/12/18/access.log"

Specifying the flag -d instructs the test program to create missing
subdirectories, for example, having created a directory 1996:

	$ cronotest -d  "%Y/%m/%d/access.log" 4
	Determining periodicity of "%Y/%m/%d/access.log"
	%Y -> yearly
	%m -> monthly
	%d -> daily
	Rotation period is per day
	Start time is Sun Dec 15 16:00:21 1996 (850665621)
	Period   1 starts at Sun Dec 15 00:00:00 1996 (850608000):  "1996/12/15/access.log"
	Creating missing components of 1996/12/15/access.log
	Testing directory "1996"
	Testing directory "1996/12"
	Directory "1996/12" does not exist -- creating
	Testing directory "1996/12/15"
	Directory "1996/12/15" does not exist -- creating
	Period   2 starts at Mon Dec 16 00:00:00 1996 (850694400):  "1996/12/16/access.log"
	Creating missing components of 1996/12/16/access.log
	Initial prefix "1996" known to exist
	Initial prefix "1996/12" known to exist
	Testing directory 1996/12/16
	Directory "1996/12/16" does not exist -- creating
	Period   3 starts at Tue Dec 17 00:00:00 1996 (850780800):  "1996/12/17/access.log"
	Creating missing components of 1996/12/17/access.log
	Initial prefix "1996" known to exist
	Initial prefix "1996/12" known to exist
	Testing directory 1996/12/17
	Directory "1996/12/17" does not exist -- creating
	Period   4 starts at Wed Dec 18 00:00:00 1996 (850867200):  "1996/12/18/access.log"
	Creating missing components of 1996/12/18/access.log
	Initial prefix "1996" known to exist
	Initial prefix "1996/12" known to exist
	Testing directory 1996/12/18
	Directory "1996/12/18" does not exist -- creating


Extra debugging code was added to cronolog at version 1.5b8 to
facilitate interactive testing.  To activate this cronolog must be
must be invoked with -x (use -x- to send debug messages to stderr).
In this mode each time it reads a message cronolog will print a
message giving the current time, the start of the next period and the
number of seconds until the start of the next period.  This option is
obviously not very useful when cronolog is being used for a production
server handling several thousands or millions of requests a day, but
can be useful for checking that cronolog is working correctly.  You
could set up a virtual server that was only used for testing and
periodically send it a request.  The -s option allows a start time to
be specified -- cronolog will pretend that that is the current time.

The following transcript shows how cronolog can be used for such a
test.  Lines prefixed by "**" are the lines I typed.  The log file
template creates a new log file every minute in a new directory.  I
specified a start time a minute before the change from GMT to BST
(British Summer Time).

 ** [andrew@icarus src]$ cronolog -x- -s "29 March 1998 00:59" \
        "tmp/%Y.%m.%d/%H:%M/%Y.%m.%d-%H:%M-access.log"
    cronolog version 1.5b8

    Copyright (C) 1997 Ford & Mason Ltd.
    This is free software; see the source for copying conditions.
    There is NO warranty; not even for MERCHANTABILITY or FITNESS
    FOR A PARTICULAR PURPOSE.

    Written by Andrew Ford <A.Ford@ford-mason.co.uk>

    The latest version can be found at:

	http://www.ford-mason.co.uk/resources/cronolog/

    Using offset of 1606971 seconds from real time
    Determining periodicity of "tmp/%Y.%m.%d/%H:%M/%Y.%m.%d-%H:%M-access.log"
    %Y -> yearly
    %m -> monthly
    %d -> daily
    %H -> hourly
    %M -> per minute
    periodicity = minute
 ** MESSAGE ONE
    1998/03/29-00:59:04 GMT (891133144): using log file \
        "tmp/1998.03.29/00:59/1998.03.29-00:59-access.log" \
        until 1998/03/29-02:00:00 BST (891133200) (for 56 secs)
    Creating missing components of "tmp/1998.03.29/00:59/1998.03.29-00:59-access.log"
    Testing directory "tmp"
    Directory "tmp" does not exist -- creating
    Testing directory "tmp/1998.03.29"
    Directory "tmp/1998.03.29" does not exist -- creating
    Testing directory "tmp/1998.03.29/00:59"
    Directory "tmp/1998.03.29/00:59" does not exist -- creating
    1998/03/29-00:59:04 GMT (891133144): wrote message; \
        next period starts at 1998/03/29-02:00:00 BST (891133200) in 56 secs
 ** MESSAGE TWO
    1998/03/29-00:59:32 GMT (891133172): wrote message; \
        next period starts at 1998/03/29-02:00:00 BST (891133200) in 28 secs
 ** MESSAGE THREE
    1998/03/29-02:00:00 BST (891133200): using log file \
        "tmp/1998.03.29/02:00/1998.03.29-02:00-access.log" \
        until 1998/03/29-02:01:00 BST (891133260) (for 60 secs)
    Creating missing components of "tmp/1998.03.29/02:00/1998.03.29-02:00-access.log"
    Initial prefix "tmp" known to exist
    Initial prefix "tmp/1998.03.29" known to exist
    Testing directory "tmp/1998.03.29/02:00"
    Directory "tmp/1998.03.29/02:00" does not exist -- creating
    1998/03/29-02:00:00 BST (891133200): wrote message; \
        next period starts at 1998/03/29-02:01:00 BST (891133260) in 60 secs

This output shows cronolog:
 * checking the periodicity of the log file template
 * creating missing directories for new log files
 * skipping stat() tests on directories it "knows" already exist
 * recalculating the time until a new log file needs to be opened