gentoo-x86/eclass/alternatives.eclass

# Copyright 1999-2003 Gentoo Technologies, Inc.
# Distributed under the terms of the GNU General Public License v2
# $Header: /home/cvsroot/gentoo-x86/eclass/alternatives.eclass,v 1.2 2003/10/07 20:26:50 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

1	# Copyright 1999-2003 Gentoo Technologies, Inc.
2	# Distributed under the terms of the GNU General Public License v2
3	# $Header: /home/cvsroot/gentoo-x86/eclass/alternatives.eclass,v 1.2 2003/10/07 20:26:50 liquidx Exp $
4
5	# Author : Alastair Tse <liquidx@gentoo.org> (03 Oct 2003)
6	# Short Desc: Creates symlink to the latest version of multiple slotted
7	# packages.
8	#
9	# Long Desc:
10	#
11	# When a package is SLOT'ed, very often we need to have a symlink to the
12	# latest version. However, depending on the order the user has merged them,
13	# more often than not, the symlink maybe clobbered by the older versions.
14	#
15	# This eclass provides a convenience function that needs to be given a
16	# list of alternatives (descending order of recent-ness) and the symlink.
17	# It will choose the latest version if can find installed and create
18	# the desired symlink.
19	#
20	# There are two ways to use this eclass. First is by declaring two variables
21	# $SOURCE and $ALTERNATIVES where $SOURCE is the symlink to be created and
22	# $ALTERNATIVES is a list of alternatives. Second way is the use the function
23	# alternatives_makesym() like the example below.
24	#
25	# Example:
26	#
27	# pkg_postinst() {
28	# alternatives_makesym "/usr/bin/python" "/usr/bin/python2.3" "/usr/bin/python2.2"
29	# }
30	#
31	# The above example will create a symlink at /usr/bin/python to either
32	# /usr/bin/python2.3 or /usr/bin/python2.2. It will choose python2.3 over
33	# python2.2 if both exist.
34	#
35	# Alternatively, you can use this function:
36	#
37	# pkg_postinst() {
38	# alternatives_auto_makesym "/usr/bin/python" "/usr/bin/python[0-9].[0-9]"
39	# }
40	#
41	# This will use bash pathname expansion to fill a list of alternatives it can
42	# link to. It is probably more robust against version upgrades. You should
43	# consider using this unless you are want to do something special.
44	#
45	ECLASS="alternatives"
46	INHERITED="$INHERITED $ECLASS"
47
48	# automatic deduction based on a symlink and a regex mask
49	alternatives_auto_makesym() {
50	local SOURCE REGEX ALT
51	local unsorted
52	SOURCE=$1
53	REGEX=$2
54
55	ALT="`ls -1 --color=never ${ROOT}${REGEX} \| sed -e "s:^${ROOT}::" \| sort -r \| xargs`"
56	if [ -n "${ALT}" ]; then
57	alternatives_makesym ${SOURCE} ${ALT}
58	else
59	eerror "regex ${REGEX} doesn't match any files."
60	fi
61	}
62
63	alternatives_makesym() {
64	local ALTERNATIVES=""
65	local SOURCE=""
66
67	# usage: alternatives_makesym <resulting symlink> [alternative targets..]
68	SOURCE=$1
69	shift
70	ALTERNATIVES=$@
71
72	# step through given alternatives from first to last
73	# and if one exists, link it and finish.
74
75	for alt in ${ALTERNATIVES}; do
76	if [ -f "${ROOT}${alt}" ]; then
77	if [ -L "${ROOT}${SOURCE}" ]; then
78	rm -f ${ROOT}${SOURCE}
79	fi
80	einfo "Linking ${alt} to ${SOURCE}"
81	# we do this instead of ${ROOT}${SOURCE} because if
82	# ROOT=/, then a symlink to //usr/bin/python confuses distutils
83	cd ${ROOT}; ln -s ${alt} ${SOURCE}
84	break
85	fi
86	done
87
88	# report any errors
89	if [ ! -L ${ROOT}${SOURCE} ]; then
90	ewarn "Unable to establish ${SOURCE} symlink"
91	elif [ ! -f "`readlink ${ROOT}${SOURCE}`" -a ! -f "${ROOT}`readlink ${ROOT}${SOURE}`" ]; then
92	ewarn "${SOURCE} is a dead symlink."
93	fi
94	}
95
96	alternatives_pkg_postinst() {
97	if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
98	alternatives_makesym ${SOURCE} ${ALTERNATIVES}
99	fi
100	}
101
102	alternatives_pkg_postrm() {
103	if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
104	alternatives_makesym ${SOURCE} ${ALTERNATIVES}
105	fi
106	}
107
108	EXPORT_FUNCTIONS pkg_postinst pkg_postrm
109