什么是“非法原住民"?在awk中? [英] What is an "illegal primary" in awk?

问题描述

Awk给我以下错误:

Awk gives me the following error:

awk: illegal primary in regular expression (?<=\>)(.*?)(?=\<) at <=\>)(.*?)(?=\<)
source line number 10 source file transpile.awk
context is
    match($0, >>>  /(?<=\>)(.*?)(?=\<)/) <<< 

但是什么是"emem"?

But what is an "illegal primary"?

推荐答案

用awk的话来说，"primary"是正则表达式的基本单位.

A "primary", in awk parlance, is the basic unit of a regex.

正则表达式由(1个或多个)分支的替代组成.每个分支都由一个(0个或多个)主键组成.

A regex consists of an alternative of (1 or more) branches. Each branch consists of a concatenation of (0 or more) primaries.

主要字符可以是普通字符(例如a)，转义的特殊字符(例如\*)，字符类([...])，点(.)或定位符(^或$)或带括号的子表达式((...)).其中大多数也可以有一个量词(?，+，*).

A primary is either a normal character (e.g. a), or an escaped special character (e.g. \*), or a character class ([...]), or a dot (.), or an anchor (^ or $), or a parenthesized subexpression ((...)). Most of these can have a quantifier (?, +, *), too.

正则表达式的问题是(?<=\>)首先解析为(，这将启动一个子组.然后，下一项需要是主要的. ?不是有效的主数据库，因此会出现错误.

The problem with your regex is that (?<=\>) parses as ( first, which starts a subgroup. The next item then needs to be a primary. ? is not a valid primary, hence you get an error.

Awk不支持先行或先行.

Awk does not support look-ahead or look-behind.

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