File: README.DEFS

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This file describes in further detail how the strips.def file is contsructed.

Strips can be defined in one of two ways. The first is standalone. Also, strips
can be provide the image URL by generating it (as from the current date) or by
searching a web page for a URL. Let's look at an example of generating first:

strip badtech
	name Badtech
	artist James Sharman
	homepage http://www.badtech.com/
	type generate
	imageurl http://www.badtech.com/a/%-y/%-m/%-d.jpg
	provides any
end

In the first line, we specify the short name of the strip that will be used to
refer to it on the command line. This must be unique. Next, "name" specifies the
name of the strip to display in the HTML output. "artist" specifies the strip
artist's name, which will be displayed on the same line as the name of the
strip. "homepage" is the address of the strip's homepage, use for the link in
the output. "type" can be either "generate" or "search". Here we are using
"generate" to generate a URL. "imageurl" is the address of the image. You are
allowed to use a number of special variables. Single letters preceeded by the
"%" symbol, such as "%Y", "%d", "%m", etc. are interpreted as date variables
and passed to the strftime function for conversion. Date variables may be used
in: homepage, searchpage, searchpattern, imageurl, baseurl, and referer.
"date --help" provides a reference that is compatible. You can also use a "$"
followed by the name of the above variables, such as "$homepage". This will
simply subsititute "http://www.badtech.com" in place of "$homepage". You can
use named variables for name, homepage, searchpage, searchpattern, imageurl,
baseurl, referer variables on homepage, searchpage, searchpattern, imageurl,
baseurl, and referer lines.


The other type of URL generation, searching, is as follows:

strip joyoftech
	name The Joy of Tech
	homepage http://www.joyoftech.com/joyoftech/
	type search
	searchpattern <IMG.+?src="(joyimages/\d+\.gif)\"
	matchpart 1
	baseurl http://www.joyoftech.com/joyoftech/
	provides latest
end

"strip", "name", and "homepage" all function as above. The difference is the
"type search" line and the lines that follow. "searchpattern" is a Perl regular
expression that must be written to match the strip's URL. Not shown is
"searchpage", which would ordinarily go above "searchpattern". This is a URL to
a web page and is only needed if the URL to the strip image is not found on the
homepage. The same special variables listed above for "imageurl" may also be
used here. "matchpart" tells the script which parenthetical section (there must
be at least one) will contain the desired URL (see man perlre on $n variables
for more). Note that this line is only mandatory for values other than 1.
"baseurl" only needs to be specified if the "searchpattern" regular expression
does not match a full URL (that is, it does not start with "http://" and contain
the host). If specified, it is prepended to whatever "searchpattern" matched.
Not shown is "urlsuffix", which will be appended to the what "searchpattern"
matched. Finally, "imageurl" can also be used here in place of "baseurl" and
"urlsuffix". It is useful when addresses to the strip image must be constructed
from a known portion and a variable portion that is searched for. Simply specify
the URL template and insert "$match" wherever you wish the result of the search
to be put. See the strips "8bit" and "pgs" for examples of how this works.

The "provides" line indicates which type of strips the definition can provide:
either "any" for a definition that can provide the strip for any given date
or "latest" for a definition that can only provide the current strip. This is
used so that the program can skip definitons that only provide the latest strip
when running with the --date option.

Two additional variables are not shown. First is "referer". Some webservers
insist that the HTTP_REFERER header be set to the address of the HTML page that
the image is on, or they will not return the image. This is to prevent other
sites from linking to the image and (presumably) scripts like this from
functioning. What the script does by default is set the HTTP_REFERER header to
the searchpage (if specified), or the homepage (if no specific searchpage was
specified). If the webserver for some reason needs a referer other than the
searchpage or homepage, it can be specified with this variable. The second
keyword is "prefetch". This was added because it seemed at one point that
sfgate required a certain page to be downloaded immediately before the strip
images could be loaded.  The syntax is simply "prefetch [URL]". Any URL
specified will be downloaded immediately before the strip image. If this URL
cannot be retrieved (error 404 from the webserver, etc), no attempt will be made
to download the strip image.

New feature: you can now put little snippets of Perl code right into the
definition. For example, the definition for The Norm uses this to generate the
day number for 14 days ago. The Norm website uses Javascript to generate the
image URL, so it couldn't be searched for and previously there was no way to
work with dates other than the current date. Here's how it works: just
insert <code:Perl code>. No need to quote the code, just put it where
"Perl code" is. Don't forget to escape any > that may happen to be in your
code.


The other method of specifying strips is to use classes. This method is used
when there are serveral strips provided by the same webserver that all have an
identical definition, except for some strip-specific elements. Classes work as
follows:

First, the class is declared:
class ucomics-srch
	homepage http://www.ucomics.com/$strip/view$1.htm
	type search
	searchpattern (/$1/(\d+)/$1(\d+)\.(gif|jpg))
	matchpart 1
	baseurl http://images.ucomics.com/comics
	provides latest
end

This is just like a strip definition, except "class" is the first line. The
value for "class" must be unique among other classes but will not conflict with
the names of strips. Strip-specific elements are specified using special
variables "$x", where "x" is a number from 0 to 9. When the definition file is
parsed, these variables are retrieved from the strip definition, shown below.

strip calvinandhobbes
	name Calvin and Hobbes
	useclass ucomics-srch
	$1 ch
end

This definition is like a normal definition except the second line is "useclass"
followed by the name of the class to use. Below that, the strip-specific "$x"
variables must be specified. Values already declared in the class can be
overridden (if necessary) by simply specifying them in the strip definition.


For your convenience, "groups" of strips may also be defined. These allow you to
use a single keyword on the command line to refer to a whole set of strips. The
construct is as follows:

>group favorites
>	desc My Favorite Comics
>	include peanuts
>	include foxtrot, userfriendly
>end

The group name must be unique among all groups, but will not conflict with
strips or classes (in fact it might be useful to have a group for each class - I
might even make that automatic). "desc" is a description of the group that will
be shown by --list. Everything after an "include" is added to the list of
strips. You may specify one or more strips per "include" line, whatever you
prefer. Groups are referenced on the command line by an "@" symbol followed by
the name (bare words not preceeded by an "@" symbol will be considered strips).
Finally, you may use "exclude [strips]" lines instead of "include" lines to
make the group contain everystrip except those specified.

Notes:

* As of 1.0.10, only date variables use the "%" symbol - everything else now
  uses "$"

* For classes, variables declared in the strip definition take precedence over
  those specified in the class, if there is any conflict

* You cannot use "$variablename" to refer to a variable below the current line
  (assuming that you use the standard order) if the referenced variable is a
  reference itself - the script only parses "$variablename" references once.
  This is a bug and is scheduled to be fixed.

* If no "searchpage" is specified for definitions of type "search", the value of
  "homepage" is used.

* If no "referer" is specified, the value of "searchpage" is used. If this has
  not been set (in the case of definitions that generate the URL or search
  definitions that use the homepage as the searchpage), the value of "homepage"
  is used.

* There may be additional problems lurking in the defintion file-parsing code.
  It currently works fairly well, but needs to be re-written properly.

* Group, strip, and class names can contain pretty much any character except
  semicolon, space, and pipe.