[英]regex for capturing path from a string with optional character ~ (perl|awk|sed|..)
I want to match everything between first and last slash /
including optional ~
before first slash.我想匹配第一个和最后一个斜杠之间的所有内容
/
包括可选的~
在第一个斜杠之前。
I used this for the first part:我在第一部分使用了这个:
echo ~~a~/dir1/di r2/b.c \
| perl -pe 's/[^\/]*(\/.*\/).*/\1/'
which produces /dir1/di r2/
.产生
/dir1/di r2/
。
This match includes the tilde:这场比赛包括波浪号:
perl -pe 's/
.* (
~ \\/.*\\/).*/\\1/'
perl -pe 's/
.* (
~ \\/.*\\/).*/\\1/'
but adding ?
但添加
?
for optional character doesn't seem to work like in these cases:在这些情况下,对于可选字符似乎不起作用:
perl -pe 's/
.* (
~? \\/.*\\/).*/\\1/'
-> /di r2/
perl -pe 's/
.* (
~? \\/.*\\/).*/\\1/'
-> /di r2/
perl -pe 's/
.* (
(?:~) \\/.*\\/).*/\\1/'
-> ~~a/dir1/di r2/bc
perl -pe 's/
.* (
(?:~) \\/.*\\/).*/\\1/'
-> ~~a/dir1/di r2/bc
What am I doing wrong?我做错了什么?
If I understood the desired output right, this works for me with or without tilde如果我正确理解了所需的输出,无论是否使用波浪号,这都适用于我
echo "path /d1/d2/43a/" | perl -nE 'm{ ( ~? (?: /.*/ | /) ) }x; say "$1"'
Prints版画
/d1/d2/43a/
Same Perl code, with a tilde before the first slash in the input相同的 Perl 代码,在输入的第一个斜杠前有一个波浪号
echo "path ~/d1/d2/43a/" | perl -nE 'm{ ( ~? (?: /.*/ | /) ) }x; say "$1"'
prints版画
~/d1/d2/43a/
Notes Use of /1
in the substitution is deprecated.注释不推荐在替换中使用
/1
。 Use $1
instead.请改用
$1
。 With {}
for the delimiters we don't have to escape /
, making it more readable (while with delimiters other than //
we can't leave out m
in front).使用
{}
作为分隔符,我们不必转义/
,使其更具可读性(而使用除//
以外的分隔符时,我们不能在前面省略m
)。 Otherwise the same works when using /
for delimiter and then escaping it inside.否则,在使用
/
作为分隔符然后将其转义到内部时,同样有效。
Update更新
To also catch a lone ~/
(or /
), the simplest change was to add that explicitly, /.*/ | /
为了同时捕获一个单独的
~/
(或/
),最简单的更改是显式添加/.*/ | /
/.*/ | /
. /.*/ | /
. In order to capture the (optinal) ~
in both cases there is a (non-capturing) grouping around this.为了在这两种情况下捕获(可选)
~
,围绕此有一个(非捕获)分组。 Removed -w
flag so no warnings are issued when the input string has no slashes at all, but only an empty line is printed.删除了
-w
标志,因此当输入字符串根本没有斜杠时不会发出警告,但只打印一个空行。
data
data
~~a~/dir1/di r2/b.c
/dir1/di r2/z.y
~/dir1/di r3/p.q
gobbledegook~/name/more/still/more/notwanted.c
xxx~//yyy
perl -ple 's%(?:^.*?)((?:^|~)/.*/).*%$1%' data
~/dir1/di r2/
/dir1/di r2/
~/dir1/di r3/
~/name/more/still/more/
~//
Is that what you needed?那是你需要的吗?
s%(?:^.*?)((?:^|~)/.*/).*%$1%
The first part, (?:^.*?)
is a non-capturing non-greedy match for an arbitrary sequence of characters at the start of the line.第一部分
(?:^.*?)
是对行首任意字符序列的非捕获非贪婪匹配。
The second part, ((?:^|~)/.*/)
, is a capturing expression that contains a non-capturing term that matches at the start of a line, or a tilde, followed by a slash and a greedy anything up to the last slash on the line.第二部分
((?:^|~)/.*/)
是一个捕获表达式,它包含一个在行首或波浪号匹配的非捕获术语,后跟一个斜杠和一个贪婪的任何东西直到最后一个斜线。
The trailing .*
matches everything after the second part.尾随的
.*
匹配第二部分之后的所有内容。
The replacement is simply what was captured;替换只是捕获的内容; the rest is Perl being Perl.
剩下的就是 Perl 就是 Perl。
The original problem statement was incomplete, it seems.原来的问题陈述似乎是不完整的。 Apparently:
显然:
for single slash it should output just
/
(with accompanying tilde if present).对于单斜杠,它应该只输出
/
(如果存在,则带有伴随的波浪号)。 For no slashes preferably empty string as there is no match.对于没有斜杠,最好是空字符串,因为没有匹配项。 … And for this case
~ab/c/df
it returns full string;... 对于这种情况,
~ab/c/df
它返回完整的字符串; instead it should return/c/
.相反,它应该返回
/c/
。
So, here is a revised script to deal with the special extra cases (what happened to 'learning how to fish'?).所以,这里有一个修改过的脚本来处理特殊的额外情况(“学习如何钓鱼”发生了什么?)。 The
~ab/c/df
case was a missing ?
~ab/c/df
案例丢失了?
qualifier on a 'start of string or tilde' grouping. “字符串开头或波浪号”分组上的限定符。
data
filedata
文件~~a~/dir1/di r2/b.c
/dir1/di r2/z.y
~/dir1/di r3/p.q
gobbledegook~/name/more/still/more/notwanted.c
xxx~//yyy
not-a-slash-in-sight
just-the-one/with-extra-info
just-the~/with-more-info
~/one-slash-at-start-with-tilde
/one-slash-at-start-without-tilde
~a b/c/d.f
perl -ple 's%^[^/]*$%%; s%(?:^[^/]*?)((?:^|~)?/)[^/]*$%$1%; s%(?:^[^/]*?)((?:^|~)?/.*/).*%$1%' data
A mildly modified of the original expression comes last.对原始表达式的轻微修改放在最后。
The first s///
looks for lines without any /
and replaces them with nothing.第一个
s///
查找没有任何/
并用空替换它们。
The second s///
looks for lines with a slash, possibly preceded by tilde or start of line, followed by non-slashes to end of line with the optional tilde and the slash.第二个
s///
查找带有斜杠的行,前面可能是波浪号或行首,然后是非斜杠到带有可选波浪号和斜杠的行尾。
The output of the first two in event of a match does not match the third s///
.匹配事件中前两个的输出与第三个
s///
不匹配。
~/dir1/di r2/
/dir1/di r2/
~/dir1/di r3/
~/name/more/still/more/
~//
/
~/
~/
/
/c/
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