This tutorial will walk you through [[writing|write]] your first ikiwiki
plugin.
-What should the plugin do? Let's make it calculate and output the Fibonachi
-sequense. To output the next number in the sequence, all a user has to do
+What should the plugin do? Let's make it calculate and output the Fibonacci
+sequence. To output the next number in the sequence, all a user has to do
is write this on a wiki page:
- [[fib ]]
+ \[[!fib]]
-When the page is built, that'll be replaced by the next number in the
-sequence.
+When the page is built, the [[ikiwiki/directive]] will be
+replaced by the next number in the sequence.
-Most of ikiwiki's plugins are written in perl, and it's currently easiest
-to write them in perl. So, open your favorite text editor, and start
+Most of ikiwiki's plugins are written in Perl, and it's currently easiest
+to write them in Perl. So, open your favorite text editor and start
editing a file named "fib.pm".
#!/usr/bin/perl
-This isn't really necessary, since fib.pm will be a perl module, but it's
+This isn't really necessary, since fib.pm will be a Perl module, but it's
nice to have. Since it's a module, the next bit is this. Notice the "fib"
at the end, matching the "fib" in the filename.
use warnings;
use strict;
- use IkiWiki 2.00;
+ use IkiWiki 3.00;
Ok, boilerplate is out of the way. Now to add the one function that ikiwiki
expects to find in any module: `import`. The import function is called when
-the module is first loaded, and what modules typically do with it is
+the module is first loaded; what modules typically do with it is
register hooks that ikiwiki will call later.
sub import {
}
This has hooked our plugin into the preprocess hook, which ikiwiki uses to
-expand [[PreprocessorDirectives|preprocessordirectives]]. Notice that "fib"
-has shown up again. It doesn't actually have to match the module name this
-time, but it generally will. This "fib" is telling ikiwiki what kind of
-PreprocessorDirective to handle, namely one that looks like this:
+expand preprocessor [[directives|ikiwiki/directive]]. Notice
+that "fib" has shown up again. It doesn't actually have to match the module
+name this time, but it generally will. This "fib" is telling ikiwiki what
+kind of preprocessor directive to handle, namely one that looks like this:
- [[fib ]]
+ [[!fib ]]
Notice the `\&preprocess`? This is how you pass a reference to a function,
and the `preprocess` function is the one that ikiwiki will call to expand
-the PreprocessorDirective. So, time to write that function:
+the preprocessor directive. So, time to write that function:
sub preprocess {
my %params=@_;
}
Whatever this function returns is what will show up on the wiki page.
-Since this is the Fibonachi sequence, returning 1 will be right for the
+Since this is the Fibonacci sequence, returning 1 will be right for the
first two calls anways, so our plugin isn't _too_ buggy. ;-) Before we fix
the bug, let's finish up the plugin.
1
-Always put this as the last line in your perl modules. Perl likes it.
+Always put this as the last line in your Perl modules. Perl likes it.
Ok, done! If you save the plugin, you can copy it to a place your ikiwiki
looks for plugins (`/usr/share/perl5/IkiWiki/Plugins/` is a good bet; see
[[install]] for the details of how to figure out where to
install it). Then configure ikiwiki to use the plugin, and you're ready to
-insert at least the first two numbers of the Fibonachi sequence on web
+insert at least the first two numbers of the Fibonacci sequence on web
pages. Behold, the power of ikiwiki! ...
----
You could stop here, if you like, and go write your own plugin that does
something more useful. Rather than leave you with a broken fib plugin
though, this tutorial will go ahead and complete it. Let's add a simple
-Fibonachi generating function to the plugin. This is right out of a
+Fibonacci generating function to the plugin. This is right out of a
textbook.
sub fib {
my $num=shift;
- return 0 if $num == 1;
- return 1 if $num == 2;
+ return 0 if $num == 0;
+ return 1 if $num == 1;
return fib($num - 1) + fib($num - 2);
}
sub preprocess {
my %params=@_;
- my $num=$last++;
+ my $num=++$last;
return fib($num);
}
Feel free to try it out with a simple page like this:
- [[fib ]], [[fib ]], [[fib ]], [[fib ]], [[fib ]]
+ [[!fib ]], [[!fib ]], [[!fib ]], [[!fib ]], [[!fib ]]
Looks like it works ok, doesn't it? That creates a page that lists:
- 1, 1, 3, 5, 8
+ 1, 1, 2, 3, 5
But what happens if there are two pages that both use fib? Try it out.
If ikiwiki builds both pages in one pass, the sequence will continue
and the standalone page another. The numbers might even skip over part of
the sequence in some cases.
-Obviously, using a global `$last` veriable was a bad idea. It would
+Obviously, using a global `$last` variable was a bad idea. It would
work ok in a more regular cgi-based wiki, which only outputs one page per
run. But since ikiwiki is a wiki *compiler*, things are a bit more
-complicated. It't not very hard to fix, though, if we do want the seqense
+complicated. It's not very hard to fix, though, if we do want the sequence
to start from 1 in every page that uses it.
my %last;
sub preprocess {
my %params=@_;
my $page=$params{destpage};
- my $num=$last{$page}++;
+ my $num=++$last{$page};
return fib($num);
}
It would be nice to be able to jump directly to a given point in the
sequence:
- \[[fib seed=20]], [[fib ]], [[fib ]]
+ \[[!fib seed=20]], [[!fib ]], [[!fib ]]
Just insert these lines of code inside `preprocess`, in the appropriate
spot:
if (exists $params{seed}) {
- $last{$page}=$params{seed}-1;
+ $last{$page}=$params{seed};
}
But this highlights another issue with the plugin. The `fib()` function is
but that's not the focus of this tutorial. Instead, let's concentrate on
making the plugin use the existing function safely. A good first step would
be a guard on how high it will go.
-
+
my %last;
sub preprocess {
if (exists $params{seed}) {
$last{$page}=$params{seed}-1;
}
- my $num=$last{$page}++;
+ my $num=++$last{$page};
if ($num > 25) {
- return "[[fib will only calculate the first 25 numbers in the sequence]]";
+ error "can only calculate the first 25 numbers in the sequence";
}
return fib($num);
}
so that the user can look at the built page and see what went wrong.
Are we done? Nope, there's still a security hole. Consider what `fib()`
-does for numbers less than 1. Or for any number that's not an integer. In
+does for numbers less than 0. Or for any number that's not an integer. In
either case, it will run forever. Here's one way to fix that:
- if (int($num) != $num || $num < 1) {
- return "[[fib positive integers only, please]]";
+ if (int($num) != $num || $num < 0) {
+ error "positive integers only, please";
}
As these security problems have demonstrated, even a simple input from the
-user needs to be checked thuroughly before being used by an ikiwiki plugin.
+user needs to be checked thoroughly before being used by an ikiwiki plugin.