我想转换/foo/bar/../ foo
是否有bash命令可以做到这一点?
编辑:在我的实际案例中,目录确实存在。
我想转换/foo/bar/../ foo
是否有bash命令可以做到这一点?
编辑:在我的实际案例中,目录确实存在。
当前回答
我最近的解决方案是:
pushd foo/bar/..
dir=`pwd`
popd
根据蒂姆·惠特科姆的回答。
其他回答
使用coreutils包中的readlink实用程序。
MY_PATH=$(readlink -f "$0")
如果你只想规范化一个路径,不管是否存在,不涉及文件系统,不解析任何链接,也不使用外部utils,这里有一个从Python的posixpath.normpath转换而来的纯Bash函数。
#!/usr/bin/env bash
# Normalize path, eliminating double slashes, etc.
# Usage: new_path="$(normpath "${old_path}")"
# Translated from Python's posixpath.normpath:
# https://github.com/python/cpython/blob/master/Lib/posixpath.py#L337
normpath() {
local IFS=/ initial_slashes='' comp comps=()
if [[ $1 == /* ]]; then
initial_slashes='/'
[[ $1 == //* && $1 != ///* ]] && initial_slashes='//'
fi
for comp in $1; do
[[ -z ${comp} || ${comp} == '.' ]] && continue
if [[ ${comp} != '..' || (-z ${initial_slashes} && ${#comps[@]} -eq 0) || (\
${#comps[@]} -gt 0 && ${comps[-1]} == '..') ]]; then
comps+=("${comp}")
elif ((${#comps[@]})); then
unset 'comps[-1]'
fi
done
comp="${initial_slashes}${comps[*]}"
printf '%s\n' "${comp:-.}"
}
例子:
new_path="$(normpath '/foo/bar/..')"
echo "${new_path}"
# /foo
normpath "relative/path/with trailing slashs////"
# relative/path/with trailing slashs
normpath "////a/../lot/././/mess////./here/./../"
# /lot/mess
normpath ""
# .
# (empty path resolved to dot)
Personally, I cannot understand why Shell, a language often used for manipulating files, doesn't offer basic functions to deal with paths. In python, we have nice libraries like os.path or pathlib, which offers a whole bunch of tools to extract filename, extension, basename, path segments, split or join paths, to get absolute or normalized paths, to determine relations between paths, to do everything without much brain. And they take care of edge cases, and they're reliable. In Shell, to do any of these, either we call external executables, or we have to reinvent wheels with these extremely rudimentary and arcane syntaxes...
由于所介绍的解决方案都不适合我,所以在文件不存在的情况下,我实现了我的想法。 André Anjos的解决方案有一个问题,路径以../../都解决错了。例如../../a/b/变成了a/b/。
function normalize_rel_path(){
local path=$1
result=""
IFS='/' read -r -a array <<< "$path"
i=0
for (( idx=${#array[@]}-1 ; idx>=0 ; idx-- )) ; do
c="${array[idx]}"
if [ -z "$c" ] || [[ "$c" == "." ]];
then
continue
fi
if [[ "$c" == ".." ]]
then
i=$((i+1))
elif [ "$i" -gt "0" ];
then
i=$((i-1))
else
if [ -z "$result" ];
then
result=$c
else
result=$c/$result
fi
fi
done
while [ "$i" -gt "0" ]; do
i=$((i-1))
result="../"$result
done
unset IFS
echo $result
}
一种可移植且可靠的解决方案是使用python,几乎所有地方都预装了python(包括Darwin)。你有两个选择:
Abspath返回一个绝对路径,但不解析符号链接: import os,sys;打印(os.path.abspath (sys.argv[1]))“路径/ /文件 Realpath返回一个绝对路径并解析符号链接,生成一个规范路径: import os,sys;打印(os.path.realpath (sys.argv[1]))“路径/ /文件
在每种情况下,路径/to/file可以是相对路径,也可以是绝对路径。
我做了一个内置函数来处理这个问题,并专注于最高的性能(为了好玩)。它不解析符号链接,因此基本上与realpath -sm相同。
## A bash-only mimic of `realpath -sm`.
## Give it path[s] as argument[s] and it will convert them to clean absolute paths
abspath () {
${*+false} && { >&2 echo $FUNCNAME: missing operand; return 1; };
local c s p IFS='/'; ## path chunk, absolute path, input path, IFS for splitting paths into chunks
local -i r=0; ## return value
for p in "$@"; do
case "$p" in ## Check for leading backslashes, identify relative/absolute path
'') ((r|=1)); continue;;
//[!/]*) >&2 echo "paths =~ ^//[^/]* are impl-defined; not my problem"; ((r|=2)); continue;;
/*) ;;
*) p="$PWD/$p";; ## Prepend the current directory to form an absolute path
esac
s='';
for c in $p; do ## Let IFS split the path at '/'s
case $c in ### NOTE: IFS is '/'; so no quotes needed here
''|.) ;; ## Skip duplicate '/'s and '/./'s
..) s="${s%/*}";; ## Trim the previous addition to the absolute path string
*) s+=/$c;; ### NOTE: No quotes here intentionally. They make no difference, it seems
esac;
done;
echo "${s:-/}"; ## If xpg_echo is set, use `echo -E` or `printf $'%s\n'` instead
done
return $r;
}
注意:这个函数不处理以//开头的路径,因为路径开头的两个双斜杠是实现定义的行为。但是,它可以很好地处理/、///等等。
这个函数似乎正确地处理了所有的边缘情况,但可能还有一些我没有处理的情况。
性能注意:当调用数千个参数时,abspath运行速度比realpath -sm慢10倍左右;当使用单个参数调用abspath时,在我的机器上,abspath的运行速度比realpath -sm快110倍,这主要是因为不需要每次都执行新程序。