正则表达式拆分 HTML 标签 [英] Regex to split HTML tags
问题描述
我有一个像这样的 HTML 字符串:
I have an HTML string like so:
<img src="http://foo"><img src="http://bar">
将其拆分为两个单独的 img 标签的正则表达式模式是什么?
What would be the regex pattern to split this into two separate img tags?
推荐答案
你有多确定你的字符串完全是那个?像这样的输入怎么样:
How sure are you that your string is exactly that? What about input like this:
<img alt=">" src="http://foo" >
<img src='http://bar' alt='<' >
这是什么编程语言?是否有某种原因您没有使用标准的 HTML 解析类来处理这个问题?当您拥有一组非常知名的输入时,正则表达式只是一种很好的方法.它们不适用于真正的 HTML,仅适用于操纵演示.
What programming language is this? Is there some reason you're not using a standard HTML-parsing class to handle this? Regexes are only a good approach when you have an extremely well-known set of inputs. They don't work for real HTML, only for rigged demos.
即使您必须使用正则表达式,也应该使用正确的语法.这很容易.我已经在无数网页上测试了以下程序.它处理我上面概述的案例 - 以及其他一两个案例.
Even if you must use a regex, you should use a proper grammatical one. This is quite easy. I've tested the following programacita on a zillion web pages. It takes care of the cases I outline above — and one or two others, too.
#!/usr/bin/perl
use 5.10.0;
use strict;
use warnings;
my $img_rx = qr{
# save capture in $+{TAG} variable
(?<TAG> (?&image_tag) )
# remainder is pure declaration
(?(DEFINE)
(?<image_tag>
(?&start_tag)
(?&might_white)
(?&attributes)
(?&might_white)
(?&end_tag)
)
(?<attributes>
(?:
(?&might_white)
(?&one_attribute)
) *
)
(?<one_attribute>
\b
(?&legal_attribute)
(?&might_white) = (?&might_white)
(?:
(?"ed_value)
| (?&unquoted_value)
)
)
(?<legal_attribute>
(?: (?&required_attribute)
| (?&optional_attribute)
| (?&standard_attribute)
| (?&event_attribute)
# for LEGAL parse only, comment out next line
| (?&illegal_attribute)
)
)
(?<illegal_attribute> \b \w+ \b )
(?<required_attribute>
alt
| src
)
(?<optional_attribute>
(?&permitted_attribute)
| (?&deprecated_attribute)
)
# NB: The white space in string literals
# below DOES NOT COUNT! It's just
# there for legibility.
(?<permitted_attribute>
height
| is map
| long desc
| use map
| width
)
(?<deprecated_attribute>
align
| border
| hspace
| vspace
)
(?<standard_attribute>
class
| dir
| id
| style
| title
| xml:lang
)
(?<event_attribute>
on abort
| on click
| on dbl click
| on mouse down
| on mouse out
| on key down
| on key press
| on key up
)
(?<unquoted_value>
(?&unwhite_chunk)
)
(?<quoted_value>
(?<quote> ["'] )
(?: (?! \k<quote> ) . ) *
\k<quote>
)
(?<unwhite_chunk>
(?:
# (?! [<>'"] )
(?! > )
\S
) +
)
(?<might_white> \s * )
(?<start_tag>
< (?&might_white)
img
\b
)
(?<end_tag>
(?&html_end_tag)
| (?&xhtml_end_tag)
)
(?<html_end_tag> > )
(?<xhtml_end_tag> / > )
)
}six;
$/ = undef;
$_ = <>; # read all input
# strip stuff we aren't supposed to look at
s{ <! DOCTYPE .*? > }{}sx;
s{ <! \[ CDATA \[ .*? \]\] > }{}gsx;
s{ <script> .*? </script> }{}gsix;
s{ <!-- .*? --> }{}gsx;
my $count = 0;
while (/$img_rx/g) {
printf "Match %d at %d: %s\n",
++$count, pos(), $+{TAG};
}
你去吧.没什么!
哎呀,考虑到在正则表达式中处理 HTML 是多么容易,你为什么要永远想要使用 HTML 解析类.☺
Gee, why would you ever want to use an HTML-parsing class, given how easily HTML can be dealt with in a regex. ☺
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