Perl正则表达式-gc修饰符是什么意思? [英] Perl Regular Expression - What does gc modifier means?

问题描述

我有一个正则表达式，可以将某些文本匹配为:

I have a regex which matches some text as:

$text =~ m/$regex/gcxs

现在，我想知道'gc'修饰符的含义:

Now I want to know what 'gc' modifier means:

我搜索并发现 gc 表示在/g匹配失败后允许继续搜索" .

我不清楚.继续搜索意味着什么?

This is not clear to me. What does continued search means?

据我了解，这意味着如果/g 搜索失败，则从头开始匹配.但是/g 修饰符不匹配整个字符串吗?

As far as I have understood, it means that start matching at the beginning if the /g search fails. But doesn't /g modififier matches the whole string?

推荐答案

/g修饰符用于记住字符串中的位置"，以便您可以递增地处理字符串.例如

The /g modifier is used to remember the "position in a string" so you can incrementally process a string. e.g.

my $txt = "abc3de";
while( $txt =~ /\G[a-z]/g )
{
    print "$&";
}
while( $txt =~ /\G./g )
{
    print "$&";
}

因为在失败的比赛中位置被重置，上面的内容将输出

Because the position is reset on a failed match, the above will output

abcabc3de

/c标志不会在失败的比赛中重置位置.因此，如果我们像这样在第一个正则表达式中添加/c

The /c flag does not reset the position on a failed match. So if we add /c to the first regex like so

my $txt = "abc3de";
while( $txt =~ /\G[a-z]/gc )
{
    print "$&";
}
while( $txt =~ /\G./g )
{
    print "$&";
}

我们最终得到

abc3de

示例代码: http://ideone.com/cC9wb

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