给定一个绝对路径或相对路径(在类unix系统中)，我希望在解析任何中间符号链接之后确定目标的完整路径。同时还可以解析~用户名符号。
如果目标是一个目录，则可以将chdir()放入该目录，然后调用getcwd()，但我确实希望从shell脚本而不是编写C helper来完成此操作。不幸的是，shell倾向于试图向用户隐藏符号链接的存在(这是OS X上的bash):
$ ls -ld foo bar
drwxr-xr-x 2 greg greg 68 Aug 11 22:36 bar
lrwxr-xr-x 1 greg greg 3 Aug 11 22:36 foo -> bar
$ cd foo
$ pwd
/Users/greg/tmp/foo
$
我想要的是一个函数resolve()，这样当从上面的例子中的tmp目录执行时，resolve("foo") == "/Users/greg/tmp/bar"。
当前回答
为了解决Mac不兼容的问题，我想到了
echo `php -r "echo realpath('foo');"`
不是很好，但是跨越了操作系统
其他回答
因为我在过去的几年里遇到过很多次这样的情况，这一次我需要一个纯粹的bash可移植版本，可以在OSX和linux上使用，我继续写了一个:
活生生的版本就在这里:
https://github.com/keen99/shell-functions/tree/master/resolve_path
但为了SO，这里是当前的版本(我觉得它经过了很好的测试..但我愿意接受反馈!)
可能不难使它为普通bourne shell (sh)工作，但我没有尝试…我太喜欢$FUNCNAME了。：）
#!/bin/bash
resolve_path() {
#I'm bash only, please!
# usage: resolve_path <a file or directory>
# follows symlinks and relative paths, returns a full real path
#
local owd="$PWD"
#echo "$FUNCNAME for $1" >&2
local opath="$1"
local npath=""
local obase=$(basename "$opath")
local odir=$(dirname "$opath")
if [[ -L "$opath" ]]
then
#it's a link.
#file or directory, we want to cd into it's dir
cd $odir
#then extract where the link points.
npath=$(readlink "$obase")
#have to -L BEFORE we -f, because -f includes -L :(
if [[ -L $npath ]]
then
#the link points to another symlink, so go follow that.
resolve_path "$npath"
#and finish out early, we're done.
return $?
#done
elif [[ -f $npath ]]
#the link points to a file.
then
#get the dir for the new file
nbase=$(basename $npath)
npath=$(dirname $npath)
cd "$npath"
ndir=$(pwd -P)
retval=0
#done
elif [[ -d $npath ]]
then
#the link points to a directory.
cd "$npath"
ndir=$(pwd -P)
retval=0
#done
else
echo "$FUNCNAME: ERROR: unknown condition inside link!!" >&2
echo "opath [[ $opath ]]" >&2
echo "npath [[ $npath ]]" >&2
return 1
fi
else
if ! [[ -e "$opath" ]]
then
echo "$FUNCNAME: $opath: No such file or directory" >&2
return 1
#and break early
elif [[ -d "$opath" ]]
then
cd "$opath"
ndir=$(pwd -P)
retval=0
#done
elif [[ -f "$opath" ]]
then
cd $odir
ndir=$(pwd -P)
nbase=$(basename "$opath")
retval=0
#done
else
echo "$FUNCNAME: ERROR: unknown condition outside link!!" >&2
echo "opath [[ $opath ]]" >&2
return 1
fi
fi
#now assemble our output
echo -n "$ndir"
if [[ "x${nbase:=}" != "x" ]]
then
echo "/$nbase"
else
echo
fi
#now return to where we were
cd "$owd"
return $retval
}
这里有一个经典的例子，感谢brew:
%% ls -l `which mvn`
lrwxr-xr-x 1 draistrick 502 29 Dec 17 10:50 /usr/local/bin/mvn@ -> ../Cellar/maven/3.2.3/bin/mvn
使用这个函数，它将返回-real- path:
%% cat test.sh
#!/bin/bash
. resolve_path.inc
echo
echo "relative symlinked path:"
which mvn
echo
echo "and the real path:"
resolve_path `which mvn`
%% test.sh
relative symlinked path:
/usr/local/bin/mvn
and the real path:
/usr/local/Cellar/maven/3.2.3/libexec/bin/mvn
下面是如何使用内联Perl脚本在MacOS/Unix中获得文件的实际路径:
FILE=$(perl -e "use Cwd qw(abs_path); print abs_path('$0')")
类似地，要获取符号链接文件的目录:
DIR=$(perl -e "use Cwd qw(abs_path); use File::Basename; print dirname(abs_path('$0'))")
这是在Bash 3.2.57中测试过的最佳解决方案:
# Read a path (similar to `readlink`) recursively, until the physical path without any links (like `cd -P`) is found.
# Accepts any existing path, prints its physical path and exits `0`, exits `1` if some contained links don't exist.
# Motivation: `${BASH_SOURCE[0]}` often contains links; using it directly to extract your project's path may fail.
#
# Example: Safely `source` a file located relative to the current script
#
# source "$(dirname "$(rreadlink "${BASH_SOURCE[0]}")")/relative/script.sh"
#Inspiration: https://stackoverflow.com/a/51089005/6307827
rreadlink () {
declare p="$1" d l
while :; do
d="$(cd -P "$(dirname "$p")" && pwd)" || return $? #absolute path without symlinks
p="$d/$(basename "$p")"
if [ -h "$p" ]; then
l="$(readlink "$p")" || break
#A link must be resolved from its fully resolved parent dir.
d="$(cd "$d" && cd -P "$(dirname "$l")" && pwd)" || return $?
p="$d/$(basename "$l")"
else
break
fi
done
printf '%s\n' "$p"
}
这是Bash中的符号链接解析器，无论链接是目录还是非目录都可以工作:
function readlinks {(
set -o errexit -o nounset
declare n=0 limit=1024 link="$1"
# If it's a directory, just skip all this.
if cd "$link" 2>/dev/null
then
pwd -P
return 0
fi
# Resolve until we are out of links (or recurse too deep).
while [[ -L $link ]] && [[ $n -lt $limit ]]
do
cd "$(dirname -- "$link")"
n=$((n + 1))
link="$(readlink -- "${link##*/}")"
done
cd "$(dirname -- "$link")"
if [[ $n -ge $limit ]]
then
echo "Recursion limit ($limit) exceeded." >&2
return 2
fi
printf '%s/%s\n' "$(pwd -P)" "${link##*/}"
)}
注意，所有的cd和set都发生在一个子shell中。
readlink -f "$path"
编者注:上述内容适用于GNU readlink和FreeBSD/PC-BSD/OpenBSD readlink，但不适用于10.11版本的OS X。 GNU readlink提供了额外的相关选项，例如-m用于解析符号链接，无论最终目标是否存在。
注意，自从GNU coreutils 8.15(2012-01-06)以来，有一个realpath程序可用，它不那么迟钝，而且比上面的程序更灵活。它还兼容同名的FreeBSD util。它还包括在两个文件之间生成相对路径的功能。
realpath $path
[管理员添加以下评论由halloleo -danorton]
对于Mac OS X(至少10.11.x)，使用不带-f选项的readlink:
readlink $path
编者注:这将不会递归地解析符号链接，因此不会报告最终目标;例如，给定指向b的符号链接a, b又指向c，这将只报告b(并且不会确保它作为绝对路径输出)。 在OS X上使用以下perl命令来填补缺少readlink -f功能的空白: perl -MCwd -le 'print Cwd::abs_path(shift)' "$path"
