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#! /bin/sh
# relpath - compute the relative path FROM -> TO
# Copyright (C) 2011 Peter Breitenlohner <tex-live@tug.org>
#
# This file is free software; the copyright holder
# gives unlimited permission to copy and/or distribute it,
# with or without modifications, as long as this notice is preserved.
# First handle the simple case that FROM is a subdirectory of TO
case $2 in
"$3"/*)
echo "X$2" | sed 's,^X'$3'/,,; s,[^/][^/]*,..,g'
exit 0;;
esac
# Now the more general case, mainly for distro builds
err () {
echo "$*" >&2
exit 1
}
test $# = 3 || err 'relpath PREF FROM TO
compute the relative path FROM -> TO
where FROM and TO are absolute paths, and
prefixed with PREF are existing directories'
chk () {
case $2 in
*' '* | *'/./'* | *'/../'*) err "'$2' contains ' ', '/./', or '/../'";;
/*) ;;
*) err "'$2' must be an absolute path";;
esac
test -d "$1$2" || err "'$1$2' not a directory"
# Normalize, remove leading and trailing /
res=`echo $2 | sed 's,^//*,,; s,//*$,,; s,///*,/,g'`
}
chk "$1" "$2"; from=$res
chk "$1" "$3"; to=$res
test "/$from" = "/$to" && { echo "."; exit 0; }
# Remove common prefix
while test "/$to" != "/"; do
test "/$from" = "/" && { echo "$to"; exit 0; }
test `echo $from | sed 's,/.*,,'` = `echo $to | sed 's,/.*,,'` || break
from=`echo $from | sed 's,[^/]*/*,,'`
to=`echo $to | sed 's,[^/]*/*,,'`
done
from=`echo $from | sed 's,[^/][^/]*,..,g'`
test "/$to" = "/" || from="$from/$to"
echo "$from"
exit 0
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