例子:

absolute="/foo/bar"
current="/foo/baz/foo"

# Magic

relative="../../bar"

我如何创造魔法(希望不是太复杂的代码…)?


当前回答

另一个解决方案,纯bash + GNU readlink,在以下上下文中易于使用:

ln -s "$(relpath "$A" "$B")" "$B"

编辑:确保“$B”是不存在或没有软链接在这种情况下,否则relpath遵循这个链接,这不是你想要的!

这几乎适用于当前所有的Linux。如果readlink -m在您这边不起作用,请尝试readlink -f。请参见https://gist.github.com/hilbix/1ec361d00a8178ae8ea0查看可能的更新:

: relpath A B
# Calculate relative path from A to B, returns true on success
# Example: ln -s "$(relpath "$A" "$B")" "$B"
relpath()
{
local X Y A
# We can create dangling softlinks
X="$(readlink -m -- "$1")" || return
Y="$(readlink -m -- "$2")" || return
X="${X%/}/"
A=""
while   Y="${Y%/*}"
        [ ".${X#"$Y"/}" = ".$X" ]
do
        A="../$A"
done
X="$A${X#"$Y"/}"
X="${X%/}"
echo "${X:-.}"
}

注:

Care was taken that it is safe against unwanted shell meta character expansion, in case filenames contain * or ?. The output is meant to be usable as the first argument to ln -s: relpath / / gives . and not the empty string relpath a a gives a, even if a happens to be a directory Most common cases were tested to give reasonable results, too. This solution uses string prefix matching, hence readlink is required to canonicalize paths. Thanks to readlink -m it works for not yet existing paths, too.

在旧系统上,readlink -m不可用,如果文件不存在,readlink -f将失败。所以你可能需要一些像这样的解决方法(未经测试!):

readlink_missing()
{
readlink -m -- "$1" && return
readlink -f -- "$1" && return
[ -e . ] && echo "$(readlink_missing "$(dirname "$1")")/$(basename "$1")"
}

这在$1包含的情况下是不正确的。或. .对于不存在的路径(如/doesnotexist/./a),但它应该涵盖大多数情况。

(用readlink_missing替换上面的readlink -m——)

编辑,因为下面是反对票

下面是一个测试,这个函数确实是正确的:

check()
{
res="$(relpath "$2" "$1")"
[ ".$res" = ".$3" ] && return
printf ':WRONG: %-10q %-10q gives %q\nCORRECT %-10q %-10q gives %q\n' "$1" "$2" "$res" "$@"
}

#     TARGET   SOURCE         RESULT
check "/A/B/C" "/A"           ".."
check "/A/B/C" "/A.x"         "../../A.x"
check "/A/B/C" "/A/B"         "."
check "/A/B/C" "/A/B/C"       "C"
check "/A/B/C" "/A/B/C/D"     "C/D"
check "/A/B/C" "/A/B/C/D/E"   "C/D/E"
check "/A/B/C" "/A/B/D"       "D"
check "/A/B/C" "/A/B/D/E"     "D/E"
check "/A/B/C" "/A/D"         "../D"
check "/A/B/C" "/A/D/E"       "../D/E"
check "/A/B/C" "/D/E/F"       "../../D/E/F"

check "/foo/baz/moo" "/foo/bar" "../bar"

困惑吗?好吧,这是正确的结果!即使你认为它不符合问题,以下是正确的证明:

check "http://example.com/foo/baz/moo" "http://example.com/foo/bar" "../bar"

毫无疑问,……/bar是从页面moo中看到的页面栏的准确且唯一正确的相对路径。其他一切都是完全错误的。

采用问题的输出很简单,显然假设current是一个目录:

absolute="/foo/bar"
current="/foo/baz/foo"
relative="../$(relpath "$absolute" "$current")"

这将返回所请求的内容。

在你感到惊讶之前,这里有一个稍微复杂一点的relpath变体(注意细微的区别),它也应该适用于url语法(因此,由于一些bash魔法,末尾/幸存下来):

# Calculate relative PATH to the given DEST from the given BASE
# In the URL case, both URLs must be absolute and have the same Scheme.
# The `SCHEME:` must not be present in the FS either.
# This way this routine works for file paths an
: relpathurl DEST BASE
relpathurl()
{
local X Y A
# We can create dangling softlinks
X="$(readlink -m -- "$1")" || return
Y="$(readlink -m -- "$2")" || return
X="${X%/}/${1#"${1%/}"}"
Y="${Y%/}${2#"${2%/}"}"
A=""
while   Y="${Y%/*}"
        [ ".${X#"$Y"/}" = ".$X" ]
do
        A="../$A"
done
X="$A${X#"$Y"/}"
X="${X%/}"
echo "${X:-.}"
}

这里有一些检查,只是为了弄清楚:它确实像所说的那样工作。

check()
{
res="$(relpathurl "$2" "$1")"
[ ".$res" = ".$3" ] && return
printf ':WRONG: %-10q %-10q gives %q\nCORRECT %-10q %-10q gives %q\n' "$1" "$2" "$res" "$@"
}

#     TARGET   SOURCE         RESULT
check "/A/B/C" "/A"           ".."
check "/A/B/C" "/A.x"         "../../A.x"
check "/A/B/C" "/A/B"         "."
check "/A/B/C" "/A/B/C"       "C"
check "/A/B/C" "/A/B/C/D"     "C/D"
check "/A/B/C" "/A/B/C/D/E"   "C/D/E"
check "/A/B/C" "/A/B/D"       "D"
check "/A/B/C" "/A/B/D/E"     "D/E"
check "/A/B/C" "/A/D"         "../D"
check "/A/B/C" "/A/D/E"       "../D/E"
check "/A/B/C" "/D/E/F"       "../../D/E/F"

check "/foo/baz/moo" "/foo/bar" "../bar"
check "http://example.com/foo/baz/moo" "http://example.com/foo/bar" "../bar"

check "http://example.com/foo/baz/moo/" "http://example.com/foo/bar" "../../bar"
check "http://example.com/foo/baz/moo"  "http://example.com/foo/bar/" "../bar/"
check "http://example.com/foo/baz/moo/"  "http://example.com/foo/bar/" "../../bar/"

下面是如何用它从问题中得到想要的结果:

absolute="/foo/bar"
current="/foo/baz/foo"
relative="$(relpathurl "$absolute" "$current/")"
echo "$relative"

如果你发现什么东西不起作用,请在下面的评论中告诉我。谢谢。

PS:

为什么relpath的论点与这里的所有其他答案相反?

如果你改变

Y="$(readlink -m -- "$2")" || return

to

Y="$(readlink -m -- "${2:-"$PWD"}")" || return

然后你可以去掉第二个参数,这样BASE就是当前目录/URL/任何东西。这只是Unix的原则。

其他回答

自2001年以来,它被内置到Perl中,因此它几乎可以在您能想象到的所有系统上工作,甚至VMS。

perl -le 'use File::Spec; print File::Spec->abs2rel(@ARGV)' FILE BASE

而且,解决方案很容易理解。

举个例子:

perl -le 'use File::Spec; print File::Spec->abs2rel(@ARGV)' $absolute $current

...会很好。

test.sh:

#!/bin/bash                                                                 

cd /home/ubuntu
touch blah
TEST=/home/ubuntu/.//blah
echo TEST=$TEST
TMP=$(readlink -e "$TEST")
echo TMP=$TMP
REL=${TMP#$(pwd)/}
echo REL=$REL

测试:

$ ./test.sh 
TEST=/home/ubuntu/.//blah
TMP=/home/ubuntu/blah
REL=blah

另一个解决方案,纯bash + GNU readlink,在以下上下文中易于使用:

ln -s "$(relpath "$A" "$B")" "$B"

编辑:确保“$B”是不存在或没有软链接在这种情况下,否则relpath遵循这个链接,这不是你想要的!

这几乎适用于当前所有的Linux。如果readlink -m在您这边不起作用,请尝试readlink -f。请参见https://gist.github.com/hilbix/1ec361d00a8178ae8ea0查看可能的更新:

: relpath A B
# Calculate relative path from A to B, returns true on success
# Example: ln -s "$(relpath "$A" "$B")" "$B"
relpath()
{
local X Y A
# We can create dangling softlinks
X="$(readlink -m -- "$1")" || return
Y="$(readlink -m -- "$2")" || return
X="${X%/}/"
A=""
while   Y="${Y%/*}"
        [ ".${X#"$Y"/}" = ".$X" ]
do
        A="../$A"
done
X="$A${X#"$Y"/}"
X="${X%/}"
echo "${X:-.}"
}

注:

Care was taken that it is safe against unwanted shell meta character expansion, in case filenames contain * or ?. The output is meant to be usable as the first argument to ln -s: relpath / / gives . and not the empty string relpath a a gives a, even if a happens to be a directory Most common cases were tested to give reasonable results, too. This solution uses string prefix matching, hence readlink is required to canonicalize paths. Thanks to readlink -m it works for not yet existing paths, too.

在旧系统上,readlink -m不可用,如果文件不存在,readlink -f将失败。所以你可能需要一些像这样的解决方法(未经测试!):

readlink_missing()
{
readlink -m -- "$1" && return
readlink -f -- "$1" && return
[ -e . ] && echo "$(readlink_missing "$(dirname "$1")")/$(basename "$1")"
}

这在$1包含的情况下是不正确的。或. .对于不存在的路径(如/doesnotexist/./a),但它应该涵盖大多数情况。

(用readlink_missing替换上面的readlink -m——)

编辑,因为下面是反对票

下面是一个测试,这个函数确实是正确的:

check()
{
res="$(relpath "$2" "$1")"
[ ".$res" = ".$3" ] && return
printf ':WRONG: %-10q %-10q gives %q\nCORRECT %-10q %-10q gives %q\n' "$1" "$2" "$res" "$@"
}

#     TARGET   SOURCE         RESULT
check "/A/B/C" "/A"           ".."
check "/A/B/C" "/A.x"         "../../A.x"
check "/A/B/C" "/A/B"         "."
check "/A/B/C" "/A/B/C"       "C"
check "/A/B/C" "/A/B/C/D"     "C/D"
check "/A/B/C" "/A/B/C/D/E"   "C/D/E"
check "/A/B/C" "/A/B/D"       "D"
check "/A/B/C" "/A/B/D/E"     "D/E"
check "/A/B/C" "/A/D"         "../D"
check "/A/B/C" "/A/D/E"       "../D/E"
check "/A/B/C" "/D/E/F"       "../../D/E/F"

check "/foo/baz/moo" "/foo/bar" "../bar"

困惑吗?好吧,这是正确的结果!即使你认为它不符合问题,以下是正确的证明:

check "http://example.com/foo/baz/moo" "http://example.com/foo/bar" "../bar"

毫无疑问,……/bar是从页面moo中看到的页面栏的准确且唯一正确的相对路径。其他一切都是完全错误的。

采用问题的输出很简单,显然假设current是一个目录:

absolute="/foo/bar"
current="/foo/baz/foo"
relative="../$(relpath "$absolute" "$current")"

这将返回所请求的内容。

在你感到惊讶之前,这里有一个稍微复杂一点的relpath变体(注意细微的区别),它也应该适用于url语法(因此,由于一些bash魔法,末尾/幸存下来):

# Calculate relative PATH to the given DEST from the given BASE
# In the URL case, both URLs must be absolute and have the same Scheme.
# The `SCHEME:` must not be present in the FS either.
# This way this routine works for file paths an
: relpathurl DEST BASE
relpathurl()
{
local X Y A
# We can create dangling softlinks
X="$(readlink -m -- "$1")" || return
Y="$(readlink -m -- "$2")" || return
X="${X%/}/${1#"${1%/}"}"
Y="${Y%/}${2#"${2%/}"}"
A=""
while   Y="${Y%/*}"
        [ ".${X#"$Y"/}" = ".$X" ]
do
        A="../$A"
done
X="$A${X#"$Y"/}"
X="${X%/}"
echo "${X:-.}"
}

这里有一些检查,只是为了弄清楚:它确实像所说的那样工作。

check()
{
res="$(relpathurl "$2" "$1")"
[ ".$res" = ".$3" ] && return
printf ':WRONG: %-10q %-10q gives %q\nCORRECT %-10q %-10q gives %q\n' "$1" "$2" "$res" "$@"
}

#     TARGET   SOURCE         RESULT
check "/A/B/C" "/A"           ".."
check "/A/B/C" "/A.x"         "../../A.x"
check "/A/B/C" "/A/B"         "."
check "/A/B/C" "/A/B/C"       "C"
check "/A/B/C" "/A/B/C/D"     "C/D"
check "/A/B/C" "/A/B/C/D/E"   "C/D/E"
check "/A/B/C" "/A/B/D"       "D"
check "/A/B/C" "/A/B/D/E"     "D/E"
check "/A/B/C" "/A/D"         "../D"
check "/A/B/C" "/A/D/E"       "../D/E"
check "/A/B/C" "/D/E/F"       "../../D/E/F"

check "/foo/baz/moo" "/foo/bar" "../bar"
check "http://example.com/foo/baz/moo" "http://example.com/foo/bar" "../bar"

check "http://example.com/foo/baz/moo/" "http://example.com/foo/bar" "../../bar"
check "http://example.com/foo/baz/moo"  "http://example.com/foo/bar/" "../bar/"
check "http://example.com/foo/baz/moo/"  "http://example.com/foo/bar/" "../../bar/"

下面是如何用它从问题中得到想要的结果:

absolute="/foo/bar"
current="/foo/baz/foo"
relative="$(relpathurl "$absolute" "$current/")"
echo "$relative"

如果你发现什么东西不起作用,请在下面的评论中告诉我。谢谢。

PS:

为什么relpath的论点与这里的所有其他答案相反?

如果你改变

Y="$(readlink -m -- "$2")" || return

to

Y="$(readlink -m -- "${2:-"$PWD"}")" || return

然后你可以去掉第二个参数,这样BASE就是当前目录/URL/任何东西。这只是Unix的原则。

$ python -c "import os.path; print os.path.relpath('/foo/bar', '/foo/baz/foo')"

给:

../../bar

下面是一个shell脚本,它可以在不调用其他程序的情况下完成:

#! /bin/env bash 

#bash script to find the relative path between two directories

mydir=${0%/}
mydir=${0%/*}
creadlink="$mydir/creadlink"

shopt -s extglob

relpath_ () {
        path1=$("$creadlink" "$1")
        path2=$("$creadlink" "$2")
        orig1=$path1
        path1=${path1%/}/
        path2=${path2%/}/

        while :; do
                if test ! "$path1"; then
                        break
                fi
                part1=${path2#$path1}
                if test "${part1#/}" = "$part1"; then
                        path1=${path1%/*}
                        continue
                fi
                if test "${path2#$path1}" = "$path2"; then
                        path1=${path1%/*}
                        continue
                fi
                break
        done
        part1=$path1
        path1=${orig1#$part1}
        depth=${path1//+([^\/])/..}
        path1=${path2#$path1}
        path1=${depth}${path2#$part1}
        path1=${path1##+(\/)}
        path1=${path1%/}
        if test ! "$path1"; then
                path1=.
        fi
        printf "$path1"

}

relpath_test () {
        res=$(relpath_ /path1/to/dir1 /path1/to/dir2 )
        expected='../dir2'
        test_results "$res" "$expected"

        res=$(relpath_ / /path1/to/dir2 )
        expected='path1/to/dir2'
        test_results "$res" "$expected"

        res=$(relpath_ /path1/to/dir2 / )
        expected='../../..'
        test_results "$res" "$expected"

        res=$(relpath_ / / )
        expected='.'
        test_results "$res" "$expected"

        res=$(relpath_ /path/to/dir2/dir3 /path/to/dir1/dir4/dir4a )
        expected='../../dir1/dir4/dir4a'
        test_results "$res" "$expected"

        res=$(relpath_ /path/to/dir1/dir4/dir4a /path/to/dir2/dir3 )
        expected='../../../dir2/dir3'
        test_results "$res" "$expected"

        #res=$(relpath_ . /path/to/dir2/dir3 )
        #expected='../../../dir2/dir3'
        #test_results "$res" "$expected"
}

test_results () {
        if test ! "$1" = "$2"; then
                printf 'failed!\nresult:\nX%sX\nexpected:\nX%sX\n\n' "$@"
        fi
}

#relpath_test

来源:http://www.ynform.org/w/Pub/Relpath