=head1 NAME

rrdcgi - Create web pages containing RRD graphs based on templates

=head1 SYNOPSIS

C<#!/path/to/>B<rrdcgi> S<[B<--filter>]>

=head1 DESCRIPTION

B<rrdcgi> is a sort of very limited script interpreter. Its purpose
is to run as a cgi-program and parse a web page template containing special
E<lt>RRD:: tags. B<rrdcgi> will interpret and act according to these tags.
In the end it will printout a web page including the necessary CGI headers.

B<rrdcgi> parses the contents of the template in 3 steps. In each step it looks
only for a subset of tags. This allows nesting of tags.

The argument parser uses the same semantics as you are used from your C-shell.

=over 8

=item B<--filter>

Assume that rrdcgi is run as a filter and not as a cgi.

=back

=head2 Keywords

=over 8

=item RRD::CV I<name>

Inserts the CGI variable of the given name.

=item RRD::CV::QUOTE I<name>

Inserts the CGI variable of the given name but quotes it, ready for
use as an argument in another RRD:: tag. So even when there are spaces in the
value of the CGI variable it will still be considered to be one argument.

=item RRD::CV::PATH I<name>

Inserts the CGI variable of the given name, quotes it and makes sure
it starts neither with a '/' nor contains '..'. This is to make
sure that no problematic pathnames can be introduced through the
CGI interface.

=item RRD::GETENV I<variable>

Get the value of an environment variable.

 <RRD::GETENV REMOTE_USER>

might give you the name of the remote user given you are using
some sort of access control on the directory.


=item RRD::GOODFOR I<seconds>

Specify the number of seconds this page should remain valid. This will prompt
the rrdcgi to output a Last-Modified, an Expire and if the number of
seconds is I<negative> a Refresh header.

=item RRD::INCLUDE I<filename>

Include the contents of the specified file into the page returned from the cgi.

=item RRD::SETENV I<variable> I<value>

If you want to present your graphs in another time zone than your own, you
could use

 <RRD::SETENV TZ UTC>

to make sure everything is presented in Universal Time. Note that the
values permitted to TZ depend on your OS.

=item RRD::SETVAR I<variable> I<value>

Analog to SETENV but for local variables.

=item RRD::GETVAR I<variable>

Analog to GETENV but for local variables.

=item RRD::TIME::LAST I<rrd-file> I<strftime-format>

This gets replaced by the last modification time of the selected RRD. The
time is I<strftime>-formatted with the string specified in the second argument.

=item RRD::TIME::NOW I<strftime-format>

This gets replaced by the current time of day. The time is
I<strftime>-formatted with the string specified in the argument.

Note that if you return : (colons) from your strftime format you may
have to escape them using \ if the time is to be used as an argument
to a GRAPH command.

=item RRD::TIME::STRFTIME I<START|END> I<start-spec> I<end-spec> I<strftime-format>

This gets replaced by a strftime-formatted time using the format
I<strftime-format> on either I<start-spec> or I<end-spec> depending on
whether I<START> or I<END> is specified.  Both I<start-spec> and I<end-spec>
must be supplied as either could be relative to the other.  This is intended
to allow pretty titles on graphs with times that are easier for non RRDtool
folks to figure out than "-2weeks".

Note that again, if you return : (colon) from your strftime format,
you may have to escape them using \ if the time is to be used as an
argument to a GRAPH command.

=item RRD::GRAPH I<rrdgraph arguments>

This tag creates the RRD graph defined by its argument and then is
replaced by an appropriate E<lt>IMG ... E<gt> tag referring to the graph.
The B<--lazy> option in RRD graph can be used to make sure that graphs
are only regenerated when they are out of date. The arguments
to the B<RRD::GRAPH> tag work as described in the B<rrdgraph> manual page.

Use the B<--lazy> option in your RRD::GRAPH tags, to reduce the load
on your server. This option makes sure that graphs are only regenerated when
the old ones are out of date.

If you do not specify your own B<--imginfo> format, the following will
be used:

 <IMG SRC="%s" WIDTH="%lu" HEIGHT="%lu">

Note that %s stands for the filename part of the graph generated, all
directories given in the PNG file argument will get dropped.

=item RRD::PRINT I<number>

If the preceding  B<RRD::GRAPH> tag contained and B<PRINT> arguments,
then you can access their output with this tag. The I<number> argument refers to the
number of the B<PRINT> argument. This first B<PRINT> has I<number> 0.

=back

=head1 EXAMPLE 1

The example below creates a web pages with a single RRD graph.

 #!/usr/local/bin/rrdcgi
 <HTML>
 <HEAD><TITLE>RRDCGI Demo</TITLE></HEAD>
 <BODY>
 <H1>RRDCGI Example Page</H1>
 <P>
 <RRD::GRAPH demo.png --lazy --title="Temperatures"
          DEF:cel=demo.rrd:exhaust:AVERAGE
          LINE2:cel#00a000:"D. Celsius">

 </P>
 </BODY>
 </HTML>

=head1 EXAMPLE 2

This script is slightly more elaborate, it allows you to run it from
a form which sets RRD_NAME. RRD_NAME is then used to select which RRD
you want to use as source for your graph.

 #!/usr/local/bin/rrdcgi
 <HTML>
 <HEAD><TITLE>RRDCGI Demo</TITLE></HEAD>
 <BODY>
 <H1>RRDCGI Example Page for <RRD::CV RRD_NAME></H1>
 <H2>Selection</H2>
 <FORM><INPUT NAME=RRD_NAME TYPE=RADIO VALUE=roomA> Room A,
       <INPUT NAME=RRD_NAME TYPE=RADIO VALUE=roomB> Room B.
       <INPUT TYPE=SUBMIT></FORM>
 <H2>Graph</H2>
 <P>
 <RRD::GRAPH <RRD::CV::PATH RRD_NAME>.png --lazy
          --title "Temperatures for "<RRD::CV::QUOTE RRD_NAME>
          DEF:cel=<RRD::CV::PATH RRD_NAME>.rrd:exhaust:AVERAGE
          LINE2:cel#00a000:"D. Celsius">

 </P>
 </BODY>
 </HTML>

=head1 EXAMPLE 3

This example shows how to handle the case where the RRD, graphs and
cgi-bins are seperate directories

 #!/.../bin/rrdcgi
 <HTML>
 <HEAD><TITLE>RRDCGI Demo</TITLE></HEAD>
 <BODY>
 <H1>RRDCGI test Page</H1>
 <RRD::GRAPH
  /.../web/pngs/testhvt.png
  --imginfo '<IMG SRC=/.../pngs/%s WIDTH=%lu HEIGHT=%lu >'
  --lazy --start -1d --end now
  DEF:http_src=/.../rrds/test.rrd:http_src:AVERAGE
  AREA:http_src#00ff00:http_src
 >
 </BODY>
 </HTML>

Note 1: Replace /.../ with the relevant directories

Note 2: The SRC=/.../pngs should be paths from the view of the
webserver/browser

=head1 AUTHOR

Tobias Oetiker E<lt>oetiker@ee.ethz.chE<gt>