source/build-aux/relpath

   1 #! /bin/sh
   2 # relpath - compute the relative path FROM -> TO
   3
   4 # Copyright (C) 2011 Peter Breitenlohner <tex-live@tug.org>
   5 #
   6 # This file is free software; the copyright holder
   7 # gives unlimited permission to copy and/or distribute it,
   8 # with or without modifications, as long as this notice is preserved.
   9
  10 # First handle the simple case that FROM is a subdirectory of TO
  11
  12 case $2 in
  13   "$3"/*)
  14     echo "X$2" | sed 's,^X'$3'/,,; s,[^/][^/]*,..,g'
  15     exit 0;;
  16 esac
  17
  18 # Now the more general case, mainly for distro builds
  19
  20 err () {
  21   echo "$*" >&2
  22   exit 1
  23 }
  24
  25 test $# = 3 || err 'relpath PREF FROM TO
  26         compute the relative path FROM -> TO
  27         where FROM and TO are absolute paths, and
  28         prefixed with PREF are existing directories'
  29
  30 chk () {
  31   case $2 in
  32     *' '* | *'/./'* | *'/../'*) err "'$2' contains ' ', '/./', or '/../'";;
  33     /*) ;;
  34     *) err "'$2' must be an absolute path";;
  35   esac
  36   test -d "$1$2" || err "'$1$2' not a directory"
  37   # Normalize, remove leading and trailing /
  38   res=`echo $2 | sed 's,^//*,,; s,//*$,,; s,///*,/,g'`
  39 }
  40
  41 chk "$1" "$2"; from=$res
  42 chk "$1" "$3"; to=$res
  43
  44 test "/$from" = "/$to" && { echo "."; exit 0; }
  45
  46 # Remove common prefix
  47 while test "/$to" != "/"; do
  48   test "/$from" = "/" && { echo "$to"; exit 0; }
  49   test `echo $from | sed 's,/.*,,'` = `echo $to | sed 's,/.*,,'` || break
  50   from=`echo $from | sed 's,[^/]*/*,,'`
  51   to=`echo $to | sed 's,[^/]*/*,,'`
  52 done
  53
  54 from=`echo $from | sed 's,[^/][^/]*,..,g'`
  55 test "/$to" = "/" || from="$from/$to"
  56
  57 echo "$from"
  58 exit 0