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140 lines
4.4 KiB
140 lines
4.4 KiB
# Copyright 1999-2011 Gentoo Foundation
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# Distributed under the terms of the GNU General Public License v2
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# $Header: /var/cvsroot/gentoo-x86/eclass/alternatives.eclass,v 1.17 2011/08/22 04:46:31 vapier Exp $
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# @ECLASS: alternatives.eclass
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# @AUTHOR:
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# Original author: Alastair Tse <liquidx@gentoo.org> (03 Oct 2003)
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# @BLURB: Creates symlink to the latest version of multiple slotted packages.
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# @DESCRIPTION:
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# When a package is SLOT'ed, very often we need to have a symlink to the
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# latest version. However, depending on the order the user has merged them,
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# more often than not, the symlink maybe clobbered by the older versions.
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#
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# This eclass provides a convenience function that needs to be given a
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# list of alternatives (descending order of recent-ness) and the symlink.
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# It will choose the latest version it can find installed and create
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# the desired symlink.
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#
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# There are two ways to use this eclass. First is by declaring two variables
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# $SOURCE and $ALTERNATIVES where $SOURCE is the symlink to be created and
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# $ALTERNATIVES is a list of alternatives. Second way is the use the function
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# alternatives_makesym() like the example below.
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# @EXAMPLE:
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# pkg_postinst() {
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# alternatives_makesym "/usr/bin/python" "/usr/bin/python2.3" "/usr/bin/python2.2"
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# }
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#
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# The above example will create a symlink at /usr/bin/python to either
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# /usr/bin/python2.3 or /usr/bin/python2.2. It will choose python2.3 over
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# python2.2 if both exist.
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#
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# Alternatively, you can use this function:
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#
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# pkg_postinst() {
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# alternatives_auto_makesym "/usr/bin/python" "/usr/bin/python[0-9].[0-9]"
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# }
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#
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# This will use bash pathname expansion to fill a list of alternatives it can
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# link to. It is probably more robust against version upgrades. You should
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# consider using this unless you are want to do something special.
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# @ECLASS-VARIABLE: SOURCE
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# @DEFAULT_UNSET
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# @DESCRIPTION:
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# The symlink to be created
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# @ECLASS-VARIABLE: ALTERNATIVES
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# @DEFAULT_UNSET
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# @DESCRIPTION:
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# The list of alternatives
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# @FUNCTION: alternatives_auto_makesym
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# @DESCRIPTION:
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# automatic deduction based on a symlink and a regex mask
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alternatives_auto_makesym() {
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local SYMLINK REGEX ALT myregex
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SYMLINK=$1
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REGEX=$2
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if [ "${REGEX:0:1}" != "/" ]
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then
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#not an absolute path:
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#inherit the root directory of our main link path for our regex search
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myregex="${SYMLINK%/*}/${REGEX}"
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else
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myregex=${REGEX}
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fi
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# sort a space delimited string by converting it to a multiline list
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# and then run sort -r over it.
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# make sure we use ${ROOT} because otherwise stage-building will break
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ALT="$(for i in $(echo ${ROOT}${myregex}); do echo ${i#${ROOT}}; done | sort -r)"
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alternatives_makesym ${SYMLINK} ${ALT}
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}
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alternatives_makesym() {
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local ALTERNATIVES=""
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local SYMLINK=""
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local alt pref
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# usage: alternatives_makesym <resulting symlink> [alternative targets..]
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SYMLINK=$1
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# this trick removes the trailing / from ${ROOT}
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pref=$(echo ${ROOT} | sed 's:/$::')
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shift
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ALTERNATIVES=$@
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# step through given alternatives from first to last
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# and if one exists, link it and finish.
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for alt in ${ALTERNATIVES}; do
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if [ -f "${pref}${alt}" ]; then
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#are files in same directory?
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if [ "${alt%/*}" = "${SYMLINK%/*}" ]
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then
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#yes; strip leading dirname from alt to create relative symlink
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einfo "Linking ${alt} to ${pref}${SYMLINK} (relative)"
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ln -sf ${alt##*/} ${pref}${SYMLINK}
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else
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#no; keep absolute path
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einfo "Linking ${alt} to ${pref}${SYMLINK} (absolute)"
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ln -sf ${pref}${alt} ${pref}${SYMLINK}
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fi
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break
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fi
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done
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# report any errors
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if [ ! -L ${pref}${SYMLINK} ]; then
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ewarn "Unable to establish ${pref}${SYMLINK} symlink"
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else
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# we need to check for either the target being in relative path form
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# or absolute path form
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if [ ! -f "`dirname ${pref}${SYMLINK}`/`readlink ${pref}${SYMLINK}`" -a \
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! -f "`readlink ${pref}${SYMLINK}`" ]; then
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ewarn "Removing dead symlink ${pref}${SYMLINK}"
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rm -f ${pref}${SYMLINK}
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fi
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fi
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}
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# @FUNCTION: alernatives-pkg_postinst
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# @DESCRIPTION:
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# The alternatives pkg_postinst, this function will be exported
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alternatives_pkg_postinst() {
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if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
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alternatives_makesym ${SOURCE} ${ALTERNATIVES}
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fi
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}
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# @FUNCTION: alternatives_pkg_postrm
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# @DESCRIPTION:
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# The alternatives pkg_postrm, this function will be exported
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alternatives_pkg_postrm() {
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if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
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alternatives_makesym ${SOURCE} ${ALTERNATIVES}
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fi
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}
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EXPORT_FUNCTIONS pkg_postinst pkg_postrm
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