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#!/bin/sh
# Determine the relative path between 2 directories. This is modeled
# on the perl File::Spec abs2rel function.
if test "x$1" = x || test "x$2" = x; then
echo "error: two paths must be supplied to $0" >&2
exit 1
fi
dir1=$1
dir2=$2
# all shell builtins except for sed; let user override
SED=${SED-sed}
# if either path is not absolute, prefix the current directory
case "$dir1" in
/*) ;;
*) dir1=$PWD/$dir1 ;;
esac
case "$dir2" in
/*) ;;
*) dir2=$PWD/$dir2 ;;
esac
# strip multiple / and trailing /
dir1=`echo $dir1 | $SED 's,//*,/,g;s,\(.\)/$,\1,'`
dir2=`echo $dir2 | $SED 's,//*,/,g;s,\(.\)/$,\1,'`
# special cases
if test "$dir1" = "$dir2"; then
# same directory, no relative path needed
exit 0
elif test "$dir1" = /; then
# convert all components of $2 to ..
dir2=`echo $dir2 | $SED 's,/[^/]*,../,g'`
echo ${dir2%/}
exit 0
elif test "$dir2" = /; then
# strip leading / of $1 to convert to relative
echo ${dir1#/}
exit 0
fi
# find the common prefix
pre1=
pre2=
while :; do
# find the leading dir component
pre1=${dir1#/}
pre1=/${pre1%%/*}
pre2=${dir2#/}
pre2=/${pre2%%/*}
# if the leading components match, strip them from the suffixes
if test "$pre1" = "$pre2"; then
dir1=${dir1#$pre1}
dir2=${dir2#$pre2}
# if either suffix is empty, we're done
if test "x$dir1" = x; then
break
elif test "x$dir2" = x; then
# dir1 is a subdir of dir2; convert to relative
dir1=${dir1#/}
break
fi
else
# we've found the common prefix
break
fi
done
# convert remaining components of $dir2 to ..
rem=
if test "x$dir2" != x; then
rem=`echo $dir2 | $SED 's,/[^/]*,../,g'`
rem=${rem%/}
fi
# print converted $dir2 + remainder of $dir1
echo $rem$dir1
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