.TH ALTERNATIVES.ECLASS 5 "Nov 2004" "Portage 2.0.51" portage
.SH NAME
alternatives \- interface for SLOT'ed packages requiring a symbolic link to the
latest version
.SH DESCRIPTION
The \fBalternatives\fR eclass provides an interface for SLOT'ed packages that 
require a symbolic link that points to the latest version installed.  Due to the
varying order in which SLOT'ed versions may be installed, the symbolic link is
not always guaranteed to point to the latest version.  The \fBalternatives\fR
eclass attempts to solve this problem.
.br

There are currently two methods in which this eclass may be used.  The first
method involves variable invocation (via \fBSOURCE\fR and \fBALTERNATIVES\fR),
while the second method involves function invocation (via \fBalternatives_makesym\fR
or \fBalternatives_auto_makesym\fR).  These will be described below, however,
please keep in mind that the two methods are not meant to be used in conjunction.
.SH VARIABLES
.TP
.B SOURCE = \fI"/usr/bin/python"\fR
Defines the name of the symbolic link that will be created to point to the 
latest installed version.
.TP
.B ALTERNATIVES = \fI"/usr/bin/python2.3 /usr/bin/python2.2"\fR
Defines a whitespace-delimited list of alternatives.  The first one found to
exist will become the target of the created symbolic link.
.SH FUNCTIONS
.TP
.B alternatives_makesym \fI< symlink > < alt1 alt2 ... >\fR
Creates the specified symbolic link to point to the first specified alternative
found to exist.  This function is normally invoked from \fBpkg_postinst\fR and
\fBpkg_postrm\fR.
.TP
.B alternatives_auto_makesym \fI< symlink > < alt_glob >\fR
A "smart" version of \fBalternatives_makesym\fR that attempts to automatically
deduce which version to link to, based on the specified alternatives glob
pattern (eg. "python[0-9].[0-9]").  Like \fBalternatives_makesym\fR, this
function is normally invoked from \fBpkg_postinst\fR and \fBpkg_postrm\fR.
.TP
\fBNOTE\fR: the following default pkg functions are only meant for use with the
variable invocation method.
.TP
.B alternatives_pkg_postinst
Default pkg_postinst that calls \fBalternatives_makesym\fR if both the
\fBSOURCE\fR and \fBALTERNATIVES\fR variables are set.
.TP
.B alternatives_pkg_postrm
Default pkg_postrm that calls \fBalternatives_makesym\fR if both the \fBSOURCE\fR
and \fBALTERNATIVES\fR variables are set.
.SH REPORTING BUGS
Please report bugs via http://bugs.gentoo.org/
.SH SEE ALSO
.BR ebuild (5)
.SH FILES
.BR /usr/portage/eclass/alternatives.eclass
.SH AUTHORS
Aaron Walker <ka0ttic@gentoo.org>
.SH CVS HEADER
$Id: /var/cvsroot/gentoo-src/portage/man/alternatives.eclass.5,v 1.1.2.1 2005/08/20 05:05:31 vapier Exp $