perl 数组grep_Perl数组Grep（）函数

向右看齐 2022-12-06 15:38 102阅读 0赞

perl 数组grep

The Perl grep() function is a filter that runs a regular expression on each element of an array and returns only the elements that evaluate as **true**. Using regular expressions can be extremely powerful and complex. The grep() functions uses the syntax @List = grep(Expression, @array).

Perl grep()函数是一个过滤器，它在数组的每个元素上运行正则表达式，并且仅返回评估为**true**的元素。 使用正则表达式可能非常强大和复杂。 grep()函数使用语法@List = grep(Expression，@array)。

## 使用Grep()函数返回真表达式 **(** Using Grep() Function to Return True Expressions **)** ##

@myNames = ('Jacob', 'Michael', 'Joshua', 'Mathew', 'Alexander', &

@grepNames = grep(/^A

Think of the @myNames array as a row of numbered boxes, going from left to right and numbered starting with a zero. The grep() function goes through each of the elements (boxes) in the array and compares their contents to the regular expression. If the result is **true**, the contents are then added to the new @grepNames array.

将@myNames数组视为一排带编号的框，从左到右并从零开始编号。 grep()函数遍历数组中的每个元素(框)，并将其内容与正则表达式进行比较。 如果结果为**true** ，则将内容添加到新的@grepNames数组中。

In the above example, the regular expression /^A/ is looking for any value that starts with a capital A. After sifting through the contents of the @myNames array, the value of @grepNames becomes ('Alexander', 'Andrew'), the only two elements that start with a capital A.

在上面的示例中，正则表达式/ ^ A /正在查找以大写字母A开头的任何值。在@myNames数组的内容中进行筛选后，@ grepNames的值变为('Alexander'，'Andrew') ，只有两个以大写字母A开头的元素。

## 反转Grep()函数中的表达式 **(** Reversing the Expression in a Grep() Function **)** ##

One quick way to make this particular function more powerful is to reverse the regular expression with the NOT operator. The regular expression then looks for elements that evaluate to **false** and moves them into the new array.

使此特定功能更强大的一种快速方法是使用NOT运算符反转正则表达式。 然后，正则表达式将查找结果为**false的**元素，并将其移动到新数组中。

@myNames = ('Jacob', 'Michael', 'Joshua', 'Mathew', 'Alexander', &

@grepNames = grep(!/^A

In the above example, the regular expression is looking for any value that does not start with a capital A. After sifting through the contents of the @myNames array, the value of @grepNames becomes ('Jacob', 'Michael', 'Joshua', 'Matthew').

在上面的示例中，正则表达式正在寻找不以大写字母A开头的任何值。在@myNames数组的内容中进行筛选后，@ grepNames的值变为('Jacob'，'Michael'，'Joshua '， '马修')。

## 关于Perl **(** About Perl **)** ##

[Perl][] is an adaptable programming language frequently used to develop web applications. Perl is an interpreted, not compiled, language, so its programs take up more CPU time than a compiled language—a problem that becomes less important as the speed of processors increases. However, writing in Perl is faster than writing in a compiled language, so the time you save is yours.

[Perl][]是一种经常用于开发Web应用程序的适应性编程语言。 Perl是一种解释性而非编译语言，因此它的程序比编译语言占用更多的CPU时间-随着处理器速度的提高，此问题变得不那么重要了。 但是，用Perl编写要比用编译语言编写要快，因此节省的时间就是您自己的。

> 翻译自: [https://www.thoughtco.com/perl-array-grep-function-quick-tutorial-2641158][https_www.thoughtco.com_perl-array-grep-function-quick-tutorial-2641158]

perl 数组grep

[Perl]: https://www.thoughtco.com/perl-4133481
[https_www.thoughtco.com_perl-array-grep-function-quick-tutorial-2641158]: https://www.thoughtco.com/perl-array-grep-function-quick-tutorial-2641158