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# Copyright 1999-2003 Gentoo Technologies, Inc.
# Distributed under the terms of the GNU General Public License v2
# $Header: /var/cvsroot/gentoo-x86/eclass/alternatives.eclass,v 1.3 2003/10/07 20:28:52 liquidx Exp $
# Author : Alastair Tse <liquidx@gentoo.org> (03 Oct 2003)
# Short Desc: Creates symlink to the latest version of multiple slotted
# packages.
#
# Long Desc:
#
# When a package is SLOT'ed, very often we need to have a symlink to the
# latest version. However, depending on the order the user has merged them,
# more often than not, the symlink maybe clobbered by the older versions.
#
# This eclass provides a convenience function that needs to be given a
# list of alternatives (descending order of recent-ness) and the symlink.
# It will choose the latest version if can find installed and create
# the desired symlink.
#
# There are two ways to use this eclass. First is by declaring two variables
# $SOURCE and $ALTERNATIVES where $SOURCE is the symlink to be created and
# $ALTERNATIVES is a list of alternatives. Second way is the use the function
# alternatives_makesym() like the example below.
#
# Example:
#
# pkg_postinst() {
# alternatives_makesym "/usr/bin/python" "/usr/bin/python2.3" "/usr/bin/python2.2"
# }
#
# The above example will create a symlink at /usr/bin/python to either
# /usr/bin/python2.3 or /usr/bin/python2.2. It will choose python2.3 over
# python2.2 if both exist.
#
# Alternatively, you can use this function:
#
# pkg_postinst() {
# alternatives_auto_makesym "/usr/bin/python" "/usr/bin/python[0-9].[0-9]"
# }
#
# This will use bash pathname expansion to fill a list of alternatives it can
# link to. It is probably more robust against version upgrades. You should
# consider using this unless you are want to do something special.
#
ECLASS="alternatives"
INHERITED="$INHERITED $ECLASS"
# automatic deduction based on a symlink and a regex mask
alternatives_auto_makesym() {
local SOURCE REGEX ALT
local unsorted
SOURCE=$1
REGEX=$2
ALT="`ls -1 --color=never ${ROOT}${REGEX} | sed -e "s:^${ROOT}::" | sort -r | xargs`"
if [ -n "${ALT}" ]; then
alternatives_makesym ${SOURCE} ${ALT}
else
eerror "regex ${REGEX} doesn't match any files."
fi
}
alternatives_makesym() {
local ALTERNATIVES=""
local SOURCE=""
# usage: alternatives_makesym <resulting symlink> [alternative targets..]
SOURCE=$1
shift
ALTERNATIVES=$@
# step through given alternatives from first to last
# and if one exists, link it and finish.
for alt in ${ALTERNATIVES}; do
if [ -f "${ROOT}${alt}" ]; then
if [ -L "${ROOT}${SOURCE}" ]; then
rm -f ${ROOT}${SOURCE}
fi
einfo "Linking ${alt} to ${SOURCE}"
# we do this instead of ${ROOT}${SOURCE} because if
# ROOT=/, then a symlink to //usr/bin/python confuses distutils
cd ${ROOT}; ln -s ${alt} ${SOURCE}
break
fi
done
# report any errors
if [ ! -L ${ROOT}${SOURCE} ]; then
ewarn "Unable to establish ${SOURCE} symlink"
elif [ ! -f "`readlink ${ROOT}${SOURCE}`" -a ! -f "${ROOT}`readlink ${ROOT}${SOURE}`" ]; then
ewarn "${SOURCE} is a dead symlink."
fi
}
alternatives_pkg_postinst() {
if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
alternatives_makesym ${SOURCE} ${ALTERNATIVES}
fi
}
alternatives_pkg_postrm() {
if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
alternatives_makesym ${SOURCE} ${ALTERNATIVES}
fi
}
EXPORT_FUNCTIONS pkg_postinst pkg_postrm
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