== Introduction ==

Filetriggers allow to run some scripts when some file has been added or removed.

The typical use cases are:

* updating /etc/ld.so.cache when some libraries have been added/removed in /usr/lib or /lib
* running update-menus to update menus of non-XDG compliant desktops when some *.desktop have been added/removed in /usr/share/applications

== Usage ==

Add the following to your macros to enable filetriggers:

<pre>
%_filetriggers_dir /var/lib/rpm/filetriggers
</pre>

Then install your watchers:

<pre>
% cat /var/lib/rpm/filetriggers/ldconfig.filter
^.(/lib|/usr/lib)/[^/]*\.so\.
% cat /var/lib/rpm/filetriggers/ldconfig.script
#!/bin/sh
ldconfig -X
% cat /var/lib/rpm/filetriggers/gtk-icon-cache-hicolor.filter
^./usr/share/icons/hicolor/
% cat /var/lib/rpm/filetriggers/gtk-icon-cache-hicolor.script
#!/bin/sh
/usr/bin/gtk-update-icon-cache --force --quiet /usr/share/icons/hicolor
</pre>

== Implementation ==

=== files-awaiting-filetriggers ===

When a package is successfully installed (or removed), rpm will append the
installed (resp. removed) files to {{file|/var/lib/rpm/files-awaiting-filetriggers}}.

The format is quite simple: <installed-or-removed> <filename>

where <installed-or-removed> ::= "+" | "-"

For example, after installing hexedit:

<pre>
+/usr/bin/hexedit
+/usr/share/doc/hexedit
+/usr/share/doc/hexedit/COPYING
+/usr/share/doc/hexedit/TODO
+/usr/share/doc/hexedit/hexedit-1.2.12.lsm
+/usr/share/man/man1/hexedit.1.lzma
</pre>

=== rpmRunFileTriggers ===

This function is called before running {{macro|%posttrans}} scriptlets. It can be
disabled using --noscripts or --notriggers (no special command line option
introduced for now).

For each {{file|%_filetriggers_dir/*.filter}}, the regexp (POSIX Extended Regular
Expression) on the first line is applied on {{file|files-awaiting-filetriggers}}. If
some files match, the corresponding {{prog|%_filetriggers_dir/<name>.script}} is
called, with matching lines passed in stdin.

Note that this is done in parallel, so multiple {{prog|<name>.script}} may be running
at the same time.

When it's done, {{file|/var/lib/rpm/files-awaiting-filetriggers}} is removed.

== Comments ==

Characteristics of this implementation :
* if the transaction is aborted, the next successful transaction will run on every succesful package installation/removal. This is due to files-awaiting-filetriggers which allows to keep state of what is done or not.
* it needs only a light patch in rpm
* files-awaiting-filetriggers may be getting big (eg: 5MB on a big transaction of 1000 packages)
* not fully integrated in rpm:
** --nofiletriggers and RPMTRANS_FLAG_NOFILETRIGGERS should be added
** a new command {{cmd|rpm --run-filetriggers}} would be useful to force running filetriggers, and only them.

Some links about filetriggers:
* triggers in dpkg: 
** http://www.dpkg.org/dpkg/Triggers
** http://lists.debian.org/debian-devel/2008/03/msg00931.html
** http://lists.debian.org/debian-dpkg/2007/04/msg00076.html
* what may get in rpm.org:
** http://www.mail-archive.com/rpm-maint@lists.rpm.org/msg00789.html
** http://www.mail-archive.com/rpm-maint@lists.rpm.org/msg00788.html