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
在这里，我提出了一个我认为是跨平台(至少Linux和macOS)的解决方案，目前对我来说效果很好。
crosspath()
{
local ref="$1"
if [ -x "$(which realpath)" ]; then
path="$(realpath "$ref")"
else
path="$(readlink -f "$ref" 2> /dev/null)"
if [ $? -gt 0 ]; then
if [ -x "$(which readlink)" ]; then
if [ ! -z "$(readlink "$ref")" ]; then
ref="$(readlink "$ref")"
fi
else
echo "realpath and readlink not available. The following may not be the final path." 1>&2
fi
if [ -d "$ref" ]; then
path="$(cd "$ref"; pwd -P)"
else
path="$(cd $(dirname "$ref"); pwd -P)/$(basename "$ref")"
fi
fi
fi
echo "$path"
}
这里有一个macOS(仅?)解决方案。也许更适合最初的问题。
mac_realpath()
{
local ref="$1"
if [[ ! -z "$(readlink "$ref")" ]]; then
ref="$(readlink "$1")"
fi
if [[ -d "$ref" ]]; then
echo "$(cd "$ref"; pwd -P)"
else
echo "$(cd $(dirname "$ref"); pwd -P)/$(basename "$ref")"
fi
}
其他回答
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。
另一种方法:
# Gets the real path of a link, following all links
myreadlink() { [ ! -h "$1" ] && echo "$1" || (local link="$(expr "$(command ls -ld -- "$1")" : '.*-> \(.*\)$')"; cd $(dirname $1); myreadlink "$link" | sed "s|^\([^/].*\)\$|$(dirname $1)/\1|"); }
# Returns the absolute path to a command, maybe in $PATH (which) or not. If not found, returns the same
whereis() { echo $1 | sed "s|^\([^/].*/.*\)|$(pwd)/\1|;s|^\([^/]*\)$|$(which -- $1)|;s|^$|$1|"; }
# Returns the realpath of a called command.
whereis_realpath() { local SCRIPT_PATH=$(whereis $1); myreadlink ${SCRIPT_PATH} | sed "s|^\([^/].*\)\$|$(dirname ${SCRIPT_PATH})/\1|"; }
把一些给定的解决方案放在一起，知道readlink在大多数系统上可用，但需要不同的参数，这对我来说在OSX和Debian上工作得很好。我对BSD系统不太确定。也许条件需要为[[$OSTYPE != darwin*]]，以仅从OSX中排除-f。
#!/bin/bash
MY_DIR=$( cd $(dirname $(readlink `[[ $OSTYPE == linux* ]] && echo "-f"` $0)) ; pwd -P)
echo "$MY_DIR"
根据标准，pwd -P应该返回已解析符号链接的路径。
C函数char *getcwd(char *buf, size_t size)从unistd.h应该有相同的行为。
getcwd 松材线虫病
