blocks|key|1287129|text|此脚本仅为不带.或..的绝对路径或相对路径的输入提供正确的结果|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1287130|#!/bin/bash

#+usage:+relpath+from+to

if+[[+"$1"+==+"$2"+]]
then
++++echo+"."
++++exit
fi

IFS="/"

current=($1)
absolute=($2)

abssize=${#absolute[@]}
cursize=${#current[@]}

while+[[+${absolute[level]}+==+${current[level]}+]]
do
++++((+level%2B%2B+))
++++if+((+level+>+abssize+%7C%7C+level+>+cursize+))
++++then
++++++++break
++++fi
done

for+((i+=+level;+i+<+cursize;+i%2B%2B))
do
++++if+((i+>+level))
++++then
++++++++newpath=$newpath"/"
++++fi
++++newpath=$newpath".."
done

for+((i+=+level;+i+<+abssize;+i%2B%2B))
do
++++if+[[+-n+$newpath+]]
++++then
++++++++newpath=$newpath"/"
++++fi
++++newpath=$newpath${absolute[i]}
done

echo+"$newpath"|code-block|syntax|javascript|1287131|entityMap^0|7|1|9|2|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

This script gives correct results only for inputs that are absolute paths or relative paths without <code>.</code> or <code>..</code>:

<pre><code>#!/bin/bash

# usage: relpath from to

if [[ "$1" == "$2" ]]
then
 echo "."
 exit
fi

IFS="/"

current=($1)
absolute=($2)

abssize=${#absolute[@]}
cursize=${#current[@]}

while [[ ${absolute[level]} == ${current[level]} ]]
do
 (( level++ ))
 if (( level &gt; abssize || level &gt; cursize ))
 then
 break
 fi
done

for ((i = level; i &lt; cursize; i++))
do
 if ((i &gt; level))
 then
 newpath=$newpath"/"
 fi
 newpath=$newpath".."
done

for ((i = level; i &lt; abssize; i++))
do
 if [[ -n $newpath ]]
 then
 newpath=$newpath"/"
 fi
 newpath=$newpath${absolute[i]}
done

echo "$newpath"
</code></pre>

blocks|key|1287179|text|下面是一个shell脚本，它无需调用其他程序即可完成此任务：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1287180|#!+/bin/env+bash+

#bash+script+to+find+the+relative+path+between+two+directories

mydir=${0%25/}
mydir=${0%25/*}
creadlink="$mydir/creadlink"

shopt+-s+extglob

relpath_+()+{
++++++++path1=$("$creadlink"+"$1")
++++++++path2=$("$creadlink"+"$2")
++++++++orig1=$path1
++++++++path1=${path1%25/}/
++++++++path2=${path2%25/}/

++++++++while+:;+do
++++++++++++++++if+test+!+"$path1";+then
++++++++++++++++++++++++break
++++++++++++++++fi
++++++++++++++++part1=${path2#$path1}
++++++++++++++++if+test+"${part1#/}"+=+"$part1";+then
++++++++++++++++++++++++path1=${path1%25/*}
++++++++++++++++++++++++continue
++++++++++++++++fi
++++++++++++++++if+test+"${path2#$path1}"+=+"$path2";+then
++++++++++++++++++++++++path1=${path1%25/*}
++++++++++++++++++++++++continue
++++++++++++++++fi
++++++++++++++++break
++++++++done
++++++++part1=$path1
++++++++path1=${orig1#$part1}
++++++++depth=${path1//%2B([%5E\/])/..}
++++++++path1=${path2#$path1}
++++++++path1=${depth}${path2#$part1}
++++++++path1=${path1##%2B(\/)}
++++++++path1=${path1%25/}
++++++++if+test+!+"$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"+=+"$2";+then
++++++++++++++++printf+'failed!\nresult:\nX%25sX\nexpected:\nX%25sX\n\n'+"$@"
++++++++fi
}

#relpath_test|code-block|syntax|javascript|1287181|来源：http://www.ynform.org/w/Pub/Relpath|offset|length|1287182|entityMap|0|LINK|mutability|MUTABLE|url|http://www.ynform.org/w/Pub/Relpath^0|0|0|3|Z|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Here's a shell script that does it without calling other programs:

<pre class="lang-sh prettyprint-override"><code>#! /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
</code></pre>

source: <a href="http://www.ynform.org/w/Pub/Relpath" rel="nofollow noreferrer">http://www.ynform.org/w/Pub/Relpath</a>

blocks|key|1287195|text|test.sh：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1287196|#!/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=$REL|code-block|syntax|javascript|1287197|测试：|1287198|$+./test.sh+
TEST=/home/ubuntu/.//blah
TMP=/home/ubuntu/blah
REL=blah|1287199|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

test.sh:

<pre><code>#!/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
</code></pre>

Testing:

<pre><code>$ ./test.sh 
TEST=/home/ubuntu/.//blah
TMP=/home/ubuntu/blah
REL=blah
</code></pre>

blocks|key|1287256|text|此脚本仅适用于路径名。它不需要任何文件存在。如果传递的路径不是绝对路径，则行为有点不寻常，但如果两个路径都是相对路径，它应该会按预期工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1287257|我只在OS-X上测试了它，所以它可能不能移植。|1287258|#!/bin/bash
set+-e
declare+SCRIPT_NAME="$(basename+$0)"
function+usage+{
++++echo+"Usage:+$SCRIPT_NAME+<base+path>+<target+file>"
++++echo+"+++++++Outputs+<target+file>+relative+to+<base+path>"
++++exit+1
}

if+[+$#+-lt+2+];+then+usage;+fi

declare+base=$1
declare+target=$2
declare+-a+base_part=()
declare+-a+target_part=()

#Split+path+elements+&+canonicalize
OFS="$IFS";+IFS='/'
bpl=0;
for+bp+in+$base;+do
++++case+"$bp"+in
++++++++".");;
++++++++"..")+let+"bpl=$bpl-1"+;;
++++++++*)+base_part[${bpl}]="$bp"+;+let+"bpl=$bpl%2B1";;
++++esac
done
tpl=0;
for+tp+in+$target;+do
++++case+"$tp"+in
++++++++".");;
++++++++"..")+let+"tpl=$tpl-1"+;;
++++++++*)+target_part[${tpl}]="$tp"+;+let+"tpl=$tpl%2B1";;
++++esac
done
IFS="$OFS"

#Count+common+prefix
common=0
for+((+i=0+;+i<$bpl+;+i%2B%2B+));+do
++++if+[+"${base_part[$i]}"+=+"${target_part[$common]}"+]+;+then
++++++++let+"common=$common%2B1"
++++else
++++++++break
++++fi
done

#Compute+number+of+directories+up
let+"updir=$bpl-$common"+%7C%7C+updir=0+#if+the+expression+is+zero,+'let'+fails

#trivial+case+(after+canonical+decomposition)
if+[+$updir+-eq+0+];+then
++++echo+.
++++exit
fi

#Print+updirs
for+((+i=0+;+i<$updir+;+i%2B%2B+));+do
++++echo+-n+../
done

#Print+remaining+path
for+((+i=$common+;+i<$tpl+;+i%2B%2B+));+do
++++if+[+$i+-ne+$common+];+then
++++++++echo+-n+"/"
++++fi
++++if+[+""+!=+"${target_part[$i]}"+]+;+then
++++++++echo+-n+"${target_part[$i]}"
++++fi
done
#One+last+newline
echo|code-block|syntax|javascript|1287259|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

This script works only on the path names. It does not require any of the files to exist. If the paths passed are not absolute, the behavior is a bit unusual, but it should work as expected if both paths are relative.

I only tested it on OS&nbsp;X, so it might not be portable.

<pre><code>#!/bin/bash
set -e
declare SCRIPT_NAME="$(basename $0)"
function usage {
 echo "Usage: $SCRIPT_NAME &lt;base path&gt; &lt;target file&gt;"
 echo " Outputs &lt;target file&gt; relative to &lt;base path&gt;"
 exit 1
}

if [ $# -lt 2 ]; then usage; fi

declare base=$1
declare target=$2
declare -a base_part=()
declare -a target_part=()

#Split path elements &amp; canonicalize
OFS="$IFS"; IFS='/'
bpl=0;
for bp in $base; do
 case "$bp" in
 ".");;
 "..") let "bpl=$bpl-1" ;;
 *) base_part[${bpl}]="$bp" ; let "bpl=$bpl+1";;
 esac
done
tpl=0;
for tp in $target; do
 case "$tp" in
 ".");;
 "..") let "tpl=$tpl-1" ;;
 *) target_part[${tpl}]="$tp" ; let "tpl=$tpl+1";;
 esac
done
IFS="$OFS"

#Count common prefix
common=0
for (( i=0 ; i&lt;$bpl ; i++ )); do
 if [ "${base_part[$i]}" = "${target_part[$common]}" ] ; then
 let "common=$common+1"
 else
 break
 fi
done

#Compute number of directories up
let "updir=$bpl-$common" || updir=0 #if the expression is zero, 'let' fails

#trivial case (after canonical decomposition)
if [ $updir -eq 0 ]; then
 echo .
 exit
fi

#Print updirs
for (( i=0 ; i&lt;$updir ; i++ )); do
 echo -n ../
done

#Print remaining path
for (( i=$common ; i&lt;$tpl ; i++ )); do
 if [ $i -ne $common ]; then
 echo -n "/"
 fi
 if [ "" != "${target_part[$i]}" ] ; then
 echo -n "${target_part[$i]}"
 fi
done
#One last newline
echo
</code></pre>

blocks|key|1287339|text|#!/bin/bash
#+both+$1+and+$2+are+absolute+paths
#+returns+$2+relative+to+$1

source=$1
target=$2

common_part=$source
back=
while+[+"${target#$common_part}"+=+"${target}"+];+do
++common_part=$(dirname+$common_part)
++back="../${back}"
done

echo+${back}${target#$common_part/}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1287340|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>#!/bin/bash
# both $1 and $2 are absolute paths
# returns $2 relative to $1

source=$1
target=$2

common_part=$source
back=
while [ "${target#$common_part}" = "${target}" ]; do
 common_part=$(dirname $common_part)
 back="../${back}"
done

echo ${back}${target#$common_part/}
</code></pre>

blocks|key|1072508|text|$+python+-c+"import+os.path;+print+os.path.relpath('/foo/bar',+'/foo/baz/foo')"|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1072509|提供：|unstyled|1072510|../../bar|1072511|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

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

gives:

<pre><code>../../bar
</code></pre>

blocks|key|1072525|text|我的解决方案是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1072526|computeRelativePath()+
{

++++Source=$(readlink+-f+${1})
++++Target=$(readlink+-f+${2})

++++local+OLDIFS=$IFS
++++IFS="/"

++++local+SourceDirectoryArray=($Source)
++++local+TargetDirectoryArray=($Target)

++++local+SourceArrayLength=$(echo+${SourceDirectoryArray[@]}+%7C+wc+-w)
++++local+TargetArrayLength=$(echo+${TargetDirectoryArray[@]}+%7C+wc+-w)

++++local+Length
++++test+$SourceArrayLength+-gt+$TargetArrayLength+&&+Length=$SourceArrayLength+%7C%7C+Length=$TargetArrayLength


++++local+Result=""
++++local+AppendToEnd=""

++++IFS=$OLDIFS

++++local+i

++++for+((i+=+0;+i+<=+$Length+%2B+1+;+i%2B%2B+))
++++do
++++++++++++if+[+"${SourceDirectoryArray[$i]}"+=+"${TargetDirectoryArray[$i]}"+]
++++++++++++then
++++++++++++++++continue++++
++++++++++++elif+[+"${SourceDirectoryArray[$i]}"+!=+""+]+&&+[+"${TargetDirectoryArray[$i]}"+!=+""+]+
++++++++++++then
++++++++++++++++AppendToEnd="${AppendToEnd}${TargetDirectoryArray[${i}]}/"
++++++++++++++++Result="${Result}../"+++++++++++++++

++++++++++++elif+[+"${SourceDirectoryArray[$i]}"+=+""+]
++++++++++++then
++++++++++++++++Result="${Result}${TargetDirectoryArray[${i}]}/"
++++++++++++else
++++++++++++++++Result="${Result}../"
++++++++++++fi
++++done

++++Result="${Result}${AppendToEnd}"

++++echo+$Result

}|code-block|syntax|javascript|1072527|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

My Solution:

<pre><code>computeRelativePath() 
{

 Source=$(readlink -f ${1})
 Target=$(readlink -f ${2})

 local OLDIFS=$IFS
 IFS="/"

 local SourceDirectoryArray=($Source)
 local TargetDirectoryArray=($Target)

 local SourceArrayLength=$(echo ${SourceDirectoryArray[@]} | wc -w)
 local TargetArrayLength=$(echo ${TargetDirectoryArray[@]} | wc -w)

 local Length
 test $SourceArrayLength -gt $TargetArrayLength &amp;&amp; Length=$SourceArrayLength || Length=$TargetArrayLength


 local Result=""
 local AppendToEnd=""

 IFS=$OLDIFS

 local i

 for ((i = 0; i &lt;= $Length + 1 ; i++ ))
 do
 if [ "${SourceDirectoryArray[$i]}" = "${TargetDirectoryArray[$i]}" ]
 then
 continue 
 elif [ "${SourceDirectoryArray[$i]}" != "" ] &amp;&amp; [ "${TargetDirectoryArray[$i]}" != "" ] 
 then
 AppendToEnd="${AppendToEnd}${TargetDirectoryArray[${i}]}/"
 Result="${Result}../" 

 elif [ "${SourceDirectoryArray[$i]}" = "" ]
 then
 Result="${Result}${TargetDirectoryArray[${i}]}/"
 else
 Result="${Result}../"
 fi
 done

 Result="${Result}${AppendToEnd}"

 echo $Result

}
</code></pre>

blocks|key|1072595|text|我猜这一个也能起到这个作用。(附带内置测试)+:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1072596|好的，预计会有一些开销，但我们在这里做的是Bourne+shell！;)|1072597|#!/bin/sh

#
#+Finding+the+relative+path+to+a+certain+file+($2),+given+the+absolute+path+($1)
#+(available+here+too+http://pastebin.com/tWWqA8aB)
#
relpath+()+{
++local++FROM="$1"
++local++++TO="`dirname++$2`"
++local++FILE="`basename+$2`"
++local++DEBUG="$3"

++local+FROMREL=""
++local+FROMUP="$FROM"
++while+[+"$FROMUP"+!=+"/"+];+do
++++local+TOUP="$TO"
++++local+TOREL=""
++++while+[+"$TOUP"+!=+"/"+];+do
++++++[+-z+"$DEBUG"+]+%7C%7C+echo+1>&2+"$DEBUG$FROMUP+=?=+$TOUP"
++++++if+[+"$FROMUP"+=+"$TOUP"+];+then
++++++++echo+"${FROMREL:-.}/$TOREL${TOREL:%2B/}$FILE"
++++++++return+0
++++++fi
++++++TOREL="`basename+$TOUP`${TOREL:%2B/}$TOREL"
++++++TOUP="`dirname+$TOUP`"
++++done
++++FROMREL="..${FROMREL:%2B/}$FROMREL"
++++FROMUP="`dirname+$FROMUP`"
++done
++echo+"${FROMREL:-.}${TOREL:%2B/}$TOREL/$FILE"
++return+0
}

relpathshow+()+{
++echo+"+-+target+$2"
++echo+"+++from+++$1"
++echo+"+++------"
++echo+"+++=>+`relpath+$1+$2+'++++++'`"
++echo+""
}

#+If+given+2+arguments,+do+as+said...
if+[+-n+"$2"+];+then
++relpath+$1+$2

#+If+only+one+given,+then+assume+current+directory
elif+[+-n+"$1"+];+then
++relpath+`pwd`+$1

#+Otherwise+perform+a+set+of+built-in+tests+to+confirm+the+validity+of+the+method!+;)
else

++relpathshow+/usr/share/emacs22/site-lisp/emacs-goodies-el+\
++++++++++++++/usr/share/emacs22/site-lisp/emacs-goodies-el/filladapt.el

++relpathshow+/usr/share/emacs23/site-lisp/emacs-goodies-el+\
++++++++++++++/usr/share/emacs22/site-lisp/emacs-goodies-el/filladapt.el

++relpathshow+/usr/bin+\
++++++++++++++/usr/share/emacs22/site-lisp/emacs-goodies-el/filladapt.el

++relpathshow+/usr/bin+\
++++++++++++++/usr/share/emacs22/site-lisp/emacs-goodies-el/filladapt.el

++relpathshow+/usr/bin/share/emacs22/site-lisp/emacs-goodies-el+\
++++++++++++++/etc/motd

++relpathshow+/+\
++++++++++++++/initrd.img
fi|code-block|syntax|javascript|1072598|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Guess this one shall do the trick too... (comes with built-in tests) :)

OK, some overhead expected, but we're doing Bourne shell here! ;) 

<pre class="lang-sh prettyprint-override"><code>#!/bin/sh

#
# Finding the relative path to a certain file ($2), given the absolute path ($1)
# (available here too http://pastebin.com/tWWqA8aB)
#
relpath () {
 local FROM="$1"
 local TO="`dirname $2`"
 local FILE="`basename $2`"
 local DEBUG="$3"

 local FROMREL=""
 local FROMUP="$FROM"
 while [ "$FROMUP" != "/" ]; do
 local TOUP="$TO"
 local TOREL=""
 while [ "$TOUP" != "/" ]; do
 [ -z "$DEBUG" ] || echo 1&gt;&amp;2 "$DEBUG$FROMUP =?= $TOUP"
 if [ "$FROMUP" = "$TOUP" ]; then
 echo "${FROMREL:-.}/$TOREL${TOREL:+/}$FILE"
 return 0
 fi
 TOREL="`basename $TOUP`${TOREL:+/}$TOREL"
 TOUP="`dirname $TOUP`"
 done
 FROMREL="..${FROMREL:+/}$FROMREL"
 FROMUP="`dirname $FROMUP`"
 done
 echo "${FROMREL:-.}${TOREL:+/}$TOREL/$FILE"
 return 0
}

relpathshow () {
 echo " - target $2"
 echo " from $1"
 echo " ------"
 echo " =&gt; `relpath $1 $2 ' '`"
 echo ""
}

# If given 2 arguments, do as said...
if [ -n "$2" ]; then
 relpath $1 $2

# If only one given, then assume current directory
elif [ -n "$1" ]; then
 relpath `pwd` $1

# Otherwise perform a set of built-in tests to confirm the validity of the method! ;)
else

 relpathshow /usr/share/emacs22/site-lisp/emacs-goodies-el \
 /usr/share/emacs22/site-lisp/emacs-goodies-el/filladapt.el

 relpathshow /usr/share/emacs23/site-lisp/emacs-goodies-el \
 /usr/share/emacs22/site-lisp/emacs-goodies-el/filladapt.el

 relpathshow /usr/bin \
 /usr/share/emacs22/site-lisp/emacs-goodies-el/filladapt.el

 relpathshow /usr/bin \
 /usr/share/emacs22/site-lisp/emacs-goodies-el/filladapt.el

 relpathshow /usr/bin/share/emacs22/site-lisp/emacs-goodies-el \
 /etc/motd

 relpathshow / \
 /initrd.img
fi
</code></pre>

blocks|key|1287481|text|我只会使用Perl来完成这个不是那么简单的任务：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1287482|absolute="/foo/bar"
current="/foo/baz/foo"

#+Perl+is+magic
relative=$(perl+-MFile::Spec+-e+'print+File::Spec->abs2rel("'$absolute'","'$current'")')|code-block|syntax|javascript|1287483|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I would just use Perl for this not-so-trivial task:

<pre><code>absolute="/foo/bar"
current="/foo/baz/foo"

# Perl is magic
relative=$(perl -MFile::Spec -e 'print File::Spec-&gt;abs2rel("'$absolute'","'$current'")')
</code></pre>

blocks|key|1072708|text|对kasku's和Pini's+answers稍有改进，它可以更好地处理空格，并允许传递相对路径：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1072709|#!/bin/bash
#+both+$1+and+$2+are+paths
#+returns+$2+relative+to+$1
absolute=`readlink+-f+"$2"`
current=`readlink+-f+"$1"`
#+Perl+is+magic
#+Quoting+horror....+spaces+cause+problems,+that's+why+we+need+the+extra+"+in+here:
relative=$(perl+-MFile::Spec+-e+"print+File::Spec->abs2rel(q($absolute),q($current))")

echo+$relative|code-block|syntax|javascript|1072710|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/9250743/562906|1|https://stackoverflow.com/a/5027832/562906^0|1|7|0|9|6|1|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]|$A|W|B|X|1|Y]]|C|$]]|$1|D|3|E|5|F|7|Z|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]|Q|$5|L|M|N|C|$O|R]]]]

A slight improvement on <a href="https://stackoverflow.com/a/9250743/562906">kasku's</a> and <a href="https://stackoverflow.com/a/5027832/562906">Pini's</a> answers, which plays nicer with spaces and allows passing relative paths:

<pre><code>#!/bin/bash
# both $1 and $2 are paths
# returns $2 relative to $1
absolute=`readlink -f "$2"`
current=`readlink -f "$1"`
# Perl is magic
# Quoting horror.... spaces cause problems, that's why we need the extra " in here:
relative=$(perl -MFile::Spec -e "print File::Spec-&gt;abs2rel(q($absolute),q($current))")

echo $relative
</code></pre>

blocks|key|1072754|text|自2001年以来，它被内置于Perl中，因此它可以在您能想象到的几乎所有系统上工作，甚至包括VMS。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1072755|perl+-e+'use+File::Spec;+print+File::Spec->abs2rel(@ARGV)+.+"\n"'+FILE+BASE|code-block|syntax|javascript|1072756|而且，这个解决方案也很容易理解。|1072757|因此，对于您的示例：|1072758|perl+-e+'use+File::Spec;+print+File::Spec->abs2rel(@ARGV)+.+"\n"'+$absolute+$current|1072759|...would工作得很好。|1072760|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Perl|1|https://en.wikipedia.org/wiki/OpenVMS^0|E|4|0|1A|3|1|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]|$A|14|B|15|1|16]]|C|$]]|$1|D|3|E|5|F|7|17|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|18|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|19|8|@]|9|@]|C|$]]|$1|M|3|N|5|F|7|1A|8|@]|9|@]|C|$G|H]]|$1|O|3|P|5|6|7|1B|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]|Y|$5|T|U|V|C|$W|Z]]]]

It is built in to <a href="http://en.wikipedia.org/wiki/Perl" rel="noreferrer">Perl</a> since 2001, so it works on nearly every system you can imagine, even <a href="https://en.wikipedia.org/wiki/OpenVMS" rel="noreferrer">VMS</a>.

<pre><code>perl -e 'use File::Spec; print File::Spec-&gt;abs2rel(@ARGV) . "\n"' FILE BASE
</code></pre>

Also, the solution is easy to understand.

So for your example:

<pre><code>perl -e 'use File::Spec; print File::Spec-&gt;abs2rel(@ARGV) . "\n"' $absolute $current
</code></pre>

...would work fine.

blocks|key|1287661|text|我需要这样的东西，但它也能解析符号链接。我发现pwd有一个用于此目的的-P标志。我的脚本的一个片段是附加的。它在shell脚本中的一个函数中，因此是$1和$2。结果值是从START_ABS到END_ABS的相对路径，它在UPDIRS变量中。将脚本cd放到每个参数目录中，以便执行pwd+-P，这也意味着要处理相对路径参数。干杯，吉姆|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1287662|SAVE_DIR="$PWD"
cd+"$1"
START_ABS=`pwd+-P`
cd+"$SAVE_DIR"
cd+"$2"
END_ABS=`pwd+-P`

START_WORK="$START_ABS"
UPDIRS=""

while+test+-n+"${START_WORK}"+-a+"${END_ABS/#${START_WORK}}"+'=='+"$END_ABS";
do
++++START_WORK=`dirname+"$START_WORK"`"/"
++++UPDIRS=${UPDIRS}"../"
done
UPDIRS="$UPDIRS${END_ABS/#${START_WORK}}"
cd+"$SAVE_DIR"|code-block|syntax|javascript|1287663|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I needed something like this but which resolved symbolic links too. I discovered that pwd has a -P flag for that purpose. A fragment of my script is appended. It's within a function in a shell script, hence the $1 and $2. The result value, which is the relative path from START_ABS to END_ABS, is in the UPDIRS variable. The script cd's into each parameter directory in order to execute the pwd -P and this also means that relative path parameters are handled. Cheers, Jim

<pre><code>SAVE_DIR="$PWD"
cd "$1"
START_ABS=`pwd -P`
cd "$SAVE_DIR"
cd "$2"
END_ABS=`pwd -P`

START_WORK="$START_ABS"
UPDIRS=""

while test -n "${START_WORK}" -a "${END_ABS/#${START_WORK}}" '==' "$END_ABS";
do
 START_WORK=`dirname "$START_WORK"`"/"
 UPDIRS=${UPDIRS}"../"
done
UPDIRS="$UPDIRS${END_ABS/#${START_WORK}}"
cd "$SAVE_DIR"
</code></pre>

blocks|key|1072877|text|我认为使用GNU+coreutils+8.23中的realpath是最简单的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1072878|$+realpath+--relative-to="$file1"+"$file2"|code-block|syntax|javascript|1072879|例如：|1072880|$+realpath+--relative-to=/usr/bin/nmap+/tmp/testing
../../../tmp/testing|1072881|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Using realpath from GNU coreutils 8.23 is the simplest, I think:

<pre><code>$ realpath --relative-to="$file1" "$file2"
</code></pre>

For example:

<pre><code>$ realpath --relative-to=/usr/bin/nmap /tmp/testing
../../../tmp/testing
</code></pre>

blocks|key|1287740|text|这是我的版本。它基于@Offirmo的answer。我使它与Dash兼容，并修复了以下测试用例故障：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1287741|./compute-relative.sh+"/a/b/c/de/f/g"+"/a/b/c/def/g/"+-->+"../..f/g/"|style|CODE|1287742|现在：|1287743|CT_FindRelativePath+"/a/b/c/de/f/g"+"/a/b/c/def/g/"+-->+"../../../def/g/"|1287744|请参阅代码：|1287745|#+both+$1+and+$2+are+absolute+paths+beginning+with+/
#+returns+relative+path+to+$2/$target+from+$1/$source
CT_FindRelativePath()
{
++++local+insource=$1
++++local+intarget=$2

++++#+Ensure+both+source+and+target+end+with+/
++++#+This+simplifies+the+inner+loop.
++++#echo+"insource+:+\"$insource\""
++++#echo+"intarget+:+\"$intarget\""
++++case+"$insource"+in
++++++++*/)+;;
++++++++*)+source="$insource"/+;;
++++esac

++++case+"$intarget"+in
++++++++*/)+;;
++++++++*)+target="$intarget"/+;;
++++esac

++++#echo+"source+:+\"$source\""
++++#echo+"target+:+\"$target\""

++++local+common_part=$source+#+for+now

++++local+result=""

++++#echo+"common_part+is+now+:+\"$common_part\""
++++#echo+"result+is+now++++++:+\"$result\""
++++#echo+"target#common_part+:+\"${target#$common_part}\""
++++while+[+"${target#$common_part}"+=+"${target}"+-a+"${common_part}"+!=+"//"+];+do
++++++++#+no+match,+means+that+candidate+common+part+is+not+correct
++++++++#+go+up+one+level+(reduce+common+part)
++++++++common_part=$(dirname+"$common_part")/
++++++++#+and+record+that+we+went+back
++++++++if+[+-z+"${result}"+];+then
++++++++++++result="../"
++++++++else
++++++++++++result="../$result"
++++++++fi
++++++++#echo+"(w)+common_part+is+now+:+\"$common_part\""
++++++++#echo+"(w)+result+is+now++++++:+\"$result\""
++++++++#echo+"(w)+target#common_part+:+\"${target#$common_part}\""
++++done

++++#echo+"(f)+common_part+is+++++:+\"$common_part\""

++++if+[+"${common_part}"+=+"//"+];+then
++++++++#+special+case+for+root+(no+common+path)
++++++++common_part="/"
++++fi

++++#+since+we+now+have+identified+the+common+part,
++++#+compute+the+non-common+part
++++forward_part="${target#$common_part}"
++++#echo+"forward_part+=+\"$forward_part\""

++++if+[+-n+"${result}"+-a+-n+"${forward_part}"+];+then
++++++++#echo+"(simple+concat)"
++++++++result="$result$forward_part"
++++elif+[+-n+"${forward_part}"+];+then
++++++++result="$forward_part"
++++fi
++++#echo+"result+=+\"$result\""

++++#+if+a+/+was+added+to+target+and+result+ends+in+/+then+remove+it+now.
++++if+[+"$intarget"+!=+"$target"+];+then
++++++++case+"$result"+in
++++++++++++*/)+result=$(echo+"$result"+%7C+awk+'{+string=substr($0,+1,+length($0)-1);+print+string;+}'+)+;;
++++++++esac
++++fi

++++echo+$result

++++return+0
}|code-block|syntax|javascript|1287746|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/587407/offirmo|1|https://stackoverflow.com/a/12498485/3257826^0|A|8|0|J|6|1|0|0|1H|1M|B|0|0|0|1F|1K|H|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@$A|13|B|14|1|15]|$A|16|B|17|1|18]]|C|$]]|$1|D|3|E|5|6|7|19|8|@$A|1A|B|1B|F|G]|$A|1C|B|1D|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|1E|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|1F|8|@$A|1G|B|1H|F|G]|$A|1I|B|1J|F|G]]|9|@]|C|$]]|$1|L|3|M|5|6|7|1K|8|@]|9|@]|C|$]]|$1|N|3|O|5|P|7|1L|8|@]|9|@]|C|$Q|R]]|$1|S|3|-4|5|6|7|1M|8|@]|9|@]|C|$]]]|T|$U|$5|V|W|X|C|$Y|Z]]|10|$5|V|W|X|C|$Y|11]]]]

Here is my version. It's based on the <a href="https://stackoverflow.com/a/12498485/3257826">answer</a> by <a href="https://stackoverflow.com/users/587407/offirmo">@Offirmo</a>. I made it Dash-compatible and fixed the following testcase failure:

<code>./compute-relative.sh "/a/b/c/de/f/g" "/a/b/c/def/g/"</code> --> <code>"../..f/g/"</code>

Now:

<code>CT_FindRelativePath "/a/b/c/de/f/g" "/a/b/c/def/g/"</code> --> <code>"../../../def/g/"</code>

See the code:

<pre><code># both $1 and $2 are absolute paths beginning with /
# returns relative path to $2/$target from $1/$source
CT_FindRelativePath()
{
 local insource=$1
 local intarget=$2

 # Ensure both source and target end with /
 # This simplifies the inner loop.
 #echo "insource : \"$insource\""
 #echo "intarget : \"$intarget\""
 case "$insource" in
 */) ;;
 *) source="$insource"/ ;;
 esac

 case "$intarget" in
 */) ;;
 *) target="$intarget"/ ;;
 esac

 #echo "source : \"$source\""
 #echo "target : \"$target\""

 local common_part=$source # for now

 local result=""

 #echo "common_part is now : \"$common_part\""
 #echo "result is now : \"$result\""
 #echo "target#common_part : \"${target#$common_part}\""
 while [ "${target#$common_part}" = "${target}" -a "${common_part}" != "//" ]; do
 # no match, means that candidate common part is not correct
 # go up one level (reduce common part)
 common_part=$(dirname "$common_part")/
 # and record that we went back
 if [ -z "${result}" ]; then
 result="../"
 else
 result="../$result"
 fi
 #echo "(w) common_part is now : \"$common_part\""
 #echo "(w) result is now : \"$result\""
 #echo "(w) target#common_part : \"${target#$common_part}\""
 done

 #echo "(f) common_part is : \"$common_part\""

 if [ "${common_part}" = "//" ]; then
 # special case for root (no common path)
 common_part="/"
 fi

 # since we now have identified the common part,
 # compute the non-common part
 forward_part="${target#$common_part}"
 #echo "forward_part = \"$forward_part\""

 if [ -n "${result}" -a -n "${forward_part}" ]; then
 #echo "(simple concat)"
 result="$result$forward_part"
 elif [ -n "${forward_part}" ]; then
 result="$forward_part"
 fi
 #echo "result = \"$result\""

 # if a / was added to target and result ends in / then remove it now.
 if [ "$intarget" != "$target" ]; then
 case "$result" in
 */) result=$(echo "$result" | awk '{ string=substr($0, 1, length($0)-1); print string; }' ) ;;
 esac
 fi

 echo $result

 return 0
}
</code></pre>

blocks|key|1287818|text|这个答案没有解决问题中的Bash部分，但是因为我尝试使用这个问题中的答案在Emacs中实现这个功能，所以我将把它抛到那里。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1287819|Emacs实际上有一个开箱即用的函数：|1287820|ELISP>+(file-relative-name+"/a/b/c"+"/a/b/c")
"."
ELISP>+(file-relative-name+"/a/b/c"+"/a/b")
"c"
ELISP>+(file-relative-name+"/a/b/c"+"/c/b")
"../../a/b/c"|code-block|syntax|javascript|1287821|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Emacs^0|11|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

This answer does not address the Bash part of the question, but because I tried to use the answers in this question to implement this functionality in <a href="http://en.wikipedia.org/wiki/Emacs" rel="nofollow">Emacs</a> I'll throw it out there.

Emacs actually has a function for this out of the box:

<pre><code>ELISP&gt; (file-relative-name "/a/b/c" "/a/b/c")
"."
ELISP&gt; (file-relative-name "/a/b/c" "/a/b")
"c"
ELISP&gt; (file-relative-name "/a/b/c" "/c/b")
"../../a/b/c"
</code></pre>

blocks|key|1287866|text|我使用的macOS在默认情况下没有realpath命令，所以我创建了一个pure+bash函数来计算它。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1287867|#!/bin/bash

##
#+print+a+relative+path+from+"source+folder"+to+"target+file"
#
#+params:
#++$1+-+target+file,+can+be+a+relative+path+or+an+absolute+path.
#++$2+-+source+folder,+can+be+a+relative+path+or+an+absolute+path.
#
#+test:
#++$+mkdir+-p+~/A/B/C/D;+touch+~/A/B/C/D/testfile.txt;+touch+~/A/B/testfile.txt
#
#++$+getRelativePath+~/A/B/C/D/testfile.txt++~/A/B
#++$+C/D/testfile.txt
#++
#++$+getRelativePath+~/A/B/testfile.txt++~/A/B/C
#++$+../testfile.txt
#
#++$+getRelativePath+~/A/B/testfile.txt++/
#++$+home/bunnier/A/B/testfile.txt+
#
function+getRelativePath(){
++++local+targetFilename=$(basename+$1)
++++local+targetFolder=$(cd+$(dirname+$1);pwd)+#+absolute+target+folder+path
++++local+currentFolder=$(cd+$2;pwd)+#+absulute+source+folder
++++local+result=.

++++while+[+"$currentFolder"+!=+"$targetFolder"+];do
++++++if+[[+"$targetFolder"+=~+"$currentFolder"*+]];then
++++++++++pointSegment=${targetFolder#$currentFolder}
++++++++++result=$result/${pointSegment#/}
++++++++++break
++++++fi++
++++++result="$result"/..
++++++currentFolder=$(dirname+$currentFolder)
++++done

++++result=$result/$targetFilename
++++echo+${result#./}
}|code-block|syntax|javascript|1287868|entityMap^0|H|8|10|9|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

I am using macOS that did not have <code>realpath</code> command by default, so I made a <code>pure bash</code> function to caculate it.
<pre class="lang-sh prettyprint-override"><code>#!/bin/bash

##
# print a relative path from &quot;source folder&quot; to &quot;target file&quot;
#
# params:
# $1 - target file, can be a relative path or an absolute path.
# $2 - source folder, can be a relative path or an absolute path.
#
# test:
# $ mkdir -p ~/A/B/C/D; touch ~/A/B/C/D/testfile.txt; touch ~/A/B/testfile.txt
#
# $ getRelativePath ~/A/B/C/D/testfile.txt ~/A/B
# $ C/D/testfile.txt
# 
# $ getRelativePath ~/A/B/testfile.txt ~/A/B/C
# $ ../testfile.txt
#
# $ getRelativePath ~/A/B/testfile.txt /
# $ home/bunnier/A/B/testfile.txt 
#
function getRelativePath(){
 local targetFilename=$(basename $1)
 local targetFolder=$(cd $(dirname $1);pwd) # absolute target folder path
 local currentFolder=$(cd $2;pwd) # absulute source folder
 local result=.

 while [ &quot;$currentFolder&quot; != &quot;$targetFolder&quot; ];do
 if [[ &quot;$targetFolder&quot; =~ &quot;$currentFolder&quot;* ]];then
 pointSegment=${targetFolder#$currentFolder}
 result=$result/${pointSegment#/}
 break
 fi 
 result=&quot;$result&quot;/..
 currentFolder=$(dirname $currentFolder)
 done

 result=$result/$targetFilename
 echo ${result#./}
}
</code></pre>

Example:

<pre><code>absolute="/foo/bar"
current="/foo/baz/foo"

# Magic

relative="../../bar"
</code></pre>

How do I create the magic (hopefully not too complicated code...)?

Convert absolute path into relative path given a current directory using Bash

Perl

示例：absolute="/foo/bar"current="/foo/baz/foo"# Magicrelative="../../bar"我如何创造魔力(希望代码不要太复杂……)？

问使用Bash将给定的当前目录的绝对路径转换为相对路径
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