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
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。
其他回答
$ python -c "import os.path; print os.path.relpath('/foo/bar', '/foo/baz/foo')"
给:
../../bar
#!/bin/sh
# Return relative path from canonical absolute dir path $1 to canonical
# absolute dir path $2 ($1 and/or $2 may end with one or no "/").
# Does only need POSIX shell builtins (no external command)
relPath () {
local common path up
common=${1%/} path=${2%/}/
while test "${path#"$common"/}" = "$path"; do
common=${common%/*} up=../$up
done
path=$up${path#"$common"/}; path=${path%/}; printf %s "${path:-.}"
}
# Return relative path from dir $1 to dir $2 (Does not impose any
# restrictions on $1 and $2 but requires GNU Core Utility "readlink"
# HINT: busybox's "readlink" does not support option '-m', only '-f'
# which requires that all but the last path component must exist)
relpath () { relPath "$(readlink -m "$1")" "$(readlink -m "$2")"; }
上面的shell脚本是受pini的启发(谢谢!)它会触发一个错误 在Stack Overflow的语法高亮显示模块中(至少在我的预览中是这样) 帧)。因此，如果高亮显示不正确，请忽略。
一些注意事项:
Removed errors and improved code without significantly increasing code length and complexity Put functionality into functions for easiness of use Kept functions POSIX compatible so that they (should) work with all POSIX shells (tested with dash, bash, and zsh in Ubuntu Linux 12.04) Used local variables only to avoid clobbering global variables and polluting the global name space Both directory paths DO NOT need to exist (requirement for my application) Pathnames may contain spaces, special characters, control characters, backslashes, tabs, ', ", ?, *, [, ], etc. Core function "relPath" uses POSIX shell builtins only but requires canonical absolute directory paths as parameters Extended function "relpath" can handle arbitrary directory paths (also relative, non-canonical) but requires external GNU core utility "readlink" Avoided builtin "echo" and used builtin "printf" instead for two reasons: Due to conflicting historical implementations of builtin "echo" it behaves differently in different shells -> POSIX recommends that printf is preferred over echo. Builtin "echo" of some POSIX shells will interpret some backslash sequences and thus corrupt pathnames containing such sequences To avoid unnecessary conversions, pathnames are used as they are returned and expected by shell and OS utilities (e.g. cd, ln, ls, find, mkdir; unlike python's "os.path.relpath" which will interpret some backslash sequences) Except for the mentioned backslash sequences the last line of function "relPath" outputs pathnames compatible to python: path=$up${path#"$common"/}; path=${path%/}; printf %s "${path:-.}" Last line can be replaced (and simplified) by line printf %s "$up${path#"$common"/}" I prefer the latter because Filenames can be directly appended to dir paths obtained by relPath, e.g.: ln -s "$(relpath "<fromDir>" "<toDir>")<file>" "<fromDir>" Symbolic links in the same dir created with this method do not have the ugly "./" prepended to the filename. If you find an error please contact linuxball (at) gmail.com and I'll try to fix it. Added regression test suite (also POSIX shell compatible)
回归测试的代码清单(只需将其附加到shell脚本):
############################################################################
# If called with 2 arguments assume they are dir paths and print rel. path #
############################################################################
test "$#" = 2 && {
printf '%s\n' "Rel. path from '$1' to '$2' is '$(relpath "$1" "$2")'."
exit 0
}
#######################################################
# If NOT called with 2 arguments run regression tests #
#######################################################
format="\t%-19s %-22s %-27s %-8s %-8s %-8s\n"
printf \
"\n\n*** Testing own and python's function with canonical absolute dirs\n\n"
printf "$format\n" \
"From Directory" "To Directory" "Rel. Path" "relPath" "relpath" "python"
IFS=
while read -r p; do
eval set -- $p
case $1 in '#'*|'') continue;; esac # Skip comments and empty lines
# q stores quoting character, use " if ' is used in path name
q="'"; case $1$2 in *"'"*) q='"';; esac
rPOk=passed rP=$(relPath "$1" "$2"); test "$rP" = "$3" || rPOk=$rP
rpOk=passed rp=$(relpath "$1" "$2"); test "$rp" = "$3" || rpOk=$rp
RPOk=passed
RP=$(python -c "import os.path; print os.path.relpath($q$2$q, $q$1$q)")
test "$RP" = "$3" || RPOk=$RP
printf \
"$format" "$q$1$q" "$q$2$q" "$q$3$q" "$q$rPOk$q" "$q$rpOk$q" "$q$RPOk$q"
done <<-"EOF"
# From directory To directory Expected relative path
'/' '/' '.'
'/usr' '/' '..'
'/usr/' '/' '..'
'/' '/usr' 'usr'
'/' '/usr/' 'usr'
'/usr' '/usr' '.'
'/usr/' '/usr' '.'
'/usr' '/usr/' '.'
'/usr/' '/usr/' '.'
'/u' '/usr' '../usr'
'/usr' '/u' '../u'
"/u'/dir" "/u'/dir" "."
"/u'" "/u'/dir" "dir"
"/u'/dir" "/u'" ".."
"/" "/u'/dir" "u'/dir"
"/u'/dir" "/" "../.."
"/u'" "/u'" "."
"/" "/u'" "u'"
"/u'" "/" ".."
'/u"/dir' '/u"/dir' '.'
'/u"' '/u"/dir' 'dir'
'/u"/dir' '/u"' '..'
'/' '/u"/dir' 'u"/dir'
'/u"/dir' '/' '../..'
'/u"' '/u"' '.'
'/' '/u"' 'u"'
'/u"' '/' '..'
'/u /dir' '/u /dir' '.'
'/u ' '/u /dir' 'dir'
'/u /dir' '/u ' '..'
'/' '/u /dir' 'u /dir'
'/u /dir' '/' '../..'
'/u ' '/u ' '.'
'/' '/u ' 'u '
'/u ' '/' '..'
'/u\n/dir' '/u\n/dir' '.'
'/u\n' '/u\n/dir' 'dir'
'/u\n/dir' '/u\n' '..'
'/' '/u\n/dir' 'u\n/dir'
'/u\n/dir' '/' '../..'
'/u\n' '/u\n' '.'
'/' '/u\n' 'u\n'
'/u\n' '/' '..'
'/ a b/å/⮀*/!' '/ a b/å/⮀/xäå/?' '../../⮀/xäå/?'
'/' '/A' 'A'
'/A' '/' '..'
'/ & / !/*/\\/E' '/' '../../../../..'
'/' '/ & / !/*/\\/E' ' & / !/*/\\/E'
'/ & / !/*/\\/E' '/ & / !/?/\\/E/F' '../../../?/\\/E/F'
'/X/Y' '/ & / !/C/\\/E/F' '../../ & / !/C/\\/E/F'
'/ & / !/C' '/A' '../../../A'
'/A / !/C' '/A /B' '../../B'
'/Â/ !/C' '/Â/ !/C' '.'
'/ & /B / C' '/ & /B / C/D' 'D'
'/ & / !/C' '/ & / !/C/\\/Ê' '\\/Ê'
'/Å/ !/C' '/Å/ !/D' '../D'
'/.A /*B/C' '/.A /*B/\\/E' '../\\/E'
'/ & / !/C' '/ & /D' '../../D'
'/ & / !/C' '/ & /\\/E' '../../\\/E'
'/ & / !/C' '/\\/E/F' '../../../\\/E/F'
'/home/p1/p2' '/home/p1/p3' '../p3'
'/home/p1/p2' '/home/p4/p5' '../../p4/p5'
'/home/p1/p2' '/work/p6/p7' '../../../work/p6/p7'
'/home/p1' '/work/p1/p2/p3/p4' '../../work/p1/p2/p3/p4'
'/home' '/work/p2/p3' '../work/p2/p3'
'/' '/work/p2/p3/p4' 'work/p2/p3/p4'
'/home/p1/p2' '/home/p1/p2/p3/p4' 'p3/p4'
'/home/p1/p2' '/home/p1/p2/p3' 'p3'
'/home/p1/p2' '/home/p1/p2' '.'
'/home/p1/p2' '/home/p1' '..'
'/home/p1/p2' '/home' '../..'
'/home/p1/p2' '/' '../../..'
'/home/p1/p2' '/work' '../../../work'
'/home/p1/p2' '/work/p1' '../../../work/p1'
'/home/p1/p2' '/work/p1/p2' '../../../work/p1/p2'
'/home/p1/p2' '/work/p1/p2/p3' '../../../work/p1/p2/p3'
'/home/p1/p2' '/work/p1/p2/p3/p4' '../../../work/p1/p2/p3/p4'
'/-' '/-' '.'
'/?' '/?' '.'
'/??' '/??' '.'
'/???' '/???' '.'
'/?*' '/?*' '.'
'/*' '/*' '.'
'/*' '/**' '../**'
'/*' '/***' '../***'
'/*.*' '/*.**' '../*.**'
'/*.???' '/*.??' '../*.??'
'/[]' '/[]' '.'
'/[a-z]*' '/[0-9]*' '../[0-9]*'
EOF
format="\t%-19s %-22s %-27s %-8s %-8s\n"
printf "\n\n*** Testing own and python's function with arbitrary dirs\n\n"
printf "$format\n" \
"From Directory" "To Directory" "Rel. Path" "relpath" "python"
IFS=
while read -r p; do
eval set -- $p
case $1 in '#'*|'') continue;; esac # Skip comments and empty lines
# q stores quoting character, use " if ' is used in path name
q="'"; case $1$2 in *"'"*) q='"';; esac
rpOk=passed rp=$(relpath "$1" "$2"); test "$rp" = "$3" || rpOk=$rp
RPOk=passed
RP=$(python -c "import os.path; print os.path.relpath($q$2$q, $q$1$q)")
test "$RP" = "$3" || RPOk=$RP
printf "$format" "$q$1$q" "$q$2$q" "$q$3$q" "$q$rpOk$q" "$q$RPOk$q"
done <<-"EOF"
# From directory To directory Expected relative path
'usr/p1/..//./p4' 'p3/../p1/p6/.././/p2' '../../p1/p2'
'./home/../../work' '..//././../dir///' '../../dir'
'home/p1/p2' 'home/p1/p3' '../p3'
'home/p1/p2' 'home/p4/p5' '../../p4/p5'
'home/p1/p2' 'work/p6/p7' '../../../work/p6/p7'
'home/p1' 'work/p1/p2/p3/p4' '../../work/p1/p2/p3/p4'
'home' 'work/p2/p3' '../work/p2/p3'
'.' 'work/p2/p3' 'work/p2/p3'
'home/p1/p2' 'home/p1/p2/p3/p4' 'p3/p4'
'home/p1/p2' 'home/p1/p2/p3' 'p3'
'home/p1/p2' 'home/p1/p2' '.'
'home/p1/p2' 'home/p1' '..'
'home/p1/p2' 'home' '../..'
'home/p1/p2' '.' '../../..'
'home/p1/p2' 'work' '../../../work'
'home/p1/p2' 'work/p1' '../../../work/p1'
'home/p1/p2' 'work/p1/p2' '../../../work/p1/p2'
'home/p1/p2' 'work/p1/p2/p3' '../../../work/p1/p2/p3'
'home/p1/p2' 'work/p1/p2/p3/p4' '../../../work/p1/p2/p3/p4'
EOF
Python的os.path.relpath作为shell函数
这个relpath练习的目标是模仿xni提出的Python 2.7的os.path.relpath函数(从Python 2.6版可用，但只能在2.7中正常工作)。因此，一些结果可能与其他答案中提供的函数不同。
(我没有在路径中测试换行符，因为它破坏了基于从ZSH调用python -c的验证。经过一些努力，这当然是可能的。)
关于Bash中的“魔法”，我很久以前就放弃了在Bash中寻找魔法，但我已经在ZSH中找到了我需要的所有魔法，然后是一些。
因此，我提出了两种实现。
第一个实现的目标是完全兼容posix。我已经在Debian 6.0.6的“挤压”上用/bin/dash测试了它。它还可以在OS X 10.8.3上完美地与/bin/sh一起工作，这实际上是伪装成POSIX shell的Bash版本3.2。
第二个实现是一个ZSH shell函数，它对路径中的多个斜杠和其他麻烦具有健壮性。如果您有可用的ZSH，这是推荐的版本，即使您是在下面给出的脚本形式中调用它(即使用#!/usr/bin/env zsh)。
最后，我编写了一个ZSH脚本，根据其他答案中提供的测试用例，验证$PATH中relpath命令的输出。我通过添加一些空格、制表符和标点符号，例如!？ *在这里和那里，还抛出了另一个测试与vim-powerline中发现的奇异UTF-8字符。
POSIX外壳函数
首先，posix兼容的shell函数。它适用于各种路径，但不清除多个斜杠或解析符号链接。
#!/bin/sh
relpath () {
[ $# -ge 1 ] && [ $# -le 2 ] || return 1
current="${2:+"$1"}"
target="${2:-"$1"}"
[ "$target" != . ] || target=/
target="/${target##/}"
[ "$current" != . ] || current=/
current="${current:="/"}"
current="/${current##/}"
appendix="${target##/}"
relative=''
while appendix="${target#"$current"/}"
[ "$current" != '/' ] && [ "$appendix" = "$target" ]; do
if [ "$current" = "$appendix" ]; then
relative="${relative:-.}"
echo "${relative#/}"
return 0
fi
current="${current%/*}"
relative="$relative${relative:+/}.."
done
relative="$relative${relative:+${appendix:+/}}${appendix#/}"
echo "$relative"
}
relpath "$@"
ZSH壳函数
现在是更加健壮的zsh版本。如果您希望它将参数解析为真实路径à la realpath -f(在Linux coreutils包中可用)，请将第3行和第4行上的:a替换为:a。
要在zsh中使用它，请删除第一行和最后一行，并将其放在$FPATH变量中的目录中。
#!/usr/bin/env zsh
relpath () {
[[ $# -ge 1 ]] && [[ $# -le 2 ]] || return 1
local target=${${2:-$1}:a} # replace `:a' by `:A` to resolve symlinks
local current=${${${2:+$1}:-$PWD}:a} # replace `:a' by `:A` to resolve symlinks
local appendix=${target#/}
local relative=''
while appendix=${target#$current/}
[[ $current != '/' ]] && [[ $appendix = $target ]]; do
if [[ $current = $appendix ]]; then
relative=${relative:-.}
print ${relative#/}
return 0
fi
current=${current%/*}
relative="$relative${relative:+/}.."
done
relative+=${relative:+${appendix:+/}}${appendix#/}
print $relative
}
relpath "$@"
测试脚本
最后是测试脚本。它接受一个选项，即-v来启用详细输出。
#!/usr/bin/env zsh
set -eu
VERBOSE=false
script_name=$(basename $0)
usage () {
print "\n Usage: $script_name SRC_PATH DESTINATION_PATH\n" >&2
exit ${1:=1}
}
vrb () { $VERBOSE && print -P ${(%)@} || return 0; }
relpath_check () {
[[ $# -ge 1 ]] && [[ $# -le 2 ]] || return 1
target=${${2:-$1}}
prefix=${${${2:+$1}:-$PWD}}
result=$(relpath $prefix $target)
# Compare with python's os.path.relpath function
py_result=$(python -c "import os.path; print os.path.relpath('$target', '$prefix')")
col='%F{green}'
if [[ $result != $py_result ]] && col='%F{red}' || $VERBOSE; then
print -P "${col}Source: '$prefix'\nDestination: '$target'%f"
print -P "${col}relpath: ${(qq)result}%f"
print -P "${col}python: ${(qq)py_result}%f\n"
fi
}
run_checks () {
print "Running checks..."
relpath_check '/ a b/å/⮀*/!' '/ a b/å/⮀/xäå/?'
relpath_check '/' '/A'
relpath_check '/A' '/'
relpath_check '/ & / !/*/\\/E' '/'
relpath_check '/' '/ & / !/*/\\/E'
relpath_check '/ & / !/*/\\/E' '/ & / !/?/\\/E/F'
relpath_check '/X/Y' '/ & / !/C/\\/E/F'
relpath_check '/ & / !/C' '/A'
relpath_check '/A / !/C' '/A /B'
relpath_check '/Â/ !/C' '/Â/ !/C'
relpath_check '/ & /B / C' '/ & /B / C/D'
relpath_check '/ & / !/C' '/ & / !/C/\\/Ê'
relpath_check '/Å/ !/C' '/Å/ !/D'
relpath_check '/.A /*B/C' '/.A /*B/\\/E'
relpath_check '/ & / !/C' '/ & /D'
relpath_check '/ & / !/C' '/ & /\\/E'
relpath_check '/ & / !/C' '/\\/E/F'
relpath_check /home/part1/part2 /home/part1/part3
relpath_check /home/part1/part2 /home/part4/part5
relpath_check /home/part1/part2 /work/part6/part7
relpath_check /home/part1 /work/part1/part2/part3/part4
relpath_check /home /work/part2/part3
relpath_check / /work/part2/part3/part4
relpath_check /home/part1/part2 /home/part1/part2/part3/part4
relpath_check /home/part1/part2 /home/part1/part2/part3
relpath_check /home/part1/part2 /home/part1/part2
relpath_check /home/part1/part2 /home/part1
relpath_check /home/part1/part2 /home
relpath_check /home/part1/part2 /
relpath_check /home/part1/part2 /work
relpath_check /home/part1/part2 /work/part1
relpath_check /home/part1/part2 /work/part1/part2
relpath_check /home/part1/part2 /work/part1/part2/part3
relpath_check /home/part1/part2 /work/part1/part2/part3/part4
relpath_check home/part1/part2 home/part1/part3
relpath_check home/part1/part2 home/part4/part5
relpath_check home/part1/part2 work/part6/part7
relpath_check home/part1 work/part1/part2/part3/part4
relpath_check home work/part2/part3
relpath_check . work/part2/part3
relpath_check home/part1/part2 home/part1/part2/part3/part4
relpath_check home/part1/part2 home/part1/part2/part3
relpath_check home/part1/part2 home/part1/part2
relpath_check home/part1/part2 home/part1
relpath_check home/part1/part2 home
relpath_check home/part1/part2 .
relpath_check home/part1/part2 work
relpath_check home/part1/part2 work/part1
relpath_check home/part1/part2 work/part1/part2
relpath_check home/part1/part2 work/part1/part2/part3
relpath_check home/part1/part2 work/part1/part2/part3/part4
print "Done with checks."
}
if [[ $# -gt 0 ]] && [[ $1 = "-v" ]]; then
VERBOSE=true
shift
fi
if [[ $# -eq 0 ]]; then
run_checks
else
VERBOSE=true
relpath_check "$@"
fi
这个脚本只对路径名有效。它不需要任何文件存在。如果传递的路径不是绝对的，那么行为就有点不寻常，但是如果两条路径都是相对的，那么应该能正常工作。
我只在OS X上测试过，所以可能不太便携。
#!/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+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="$OFS"
#Count common prefix
common=0
for (( i=0 ; i<$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 [ $updir -eq 0 ]; then
echo .
exit
fi
#Print updirs
for (( i=0 ; i<$updir ; i++ )); do
echo -n ../
done
#Print remaining path
for (( i=$common ; i<$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
在bash中:
realDir=''
cd $(dirname $0) || exit
realDir=$(pwd)
cd -
echo $realDir
