Ruby Regular Expressions

Regular expressions are a special character sequence, which through the use of a special syntax patterns to match or find a collection of strings.

Regular expressions are used a number of pre-defined combinations of certain characters, and these particular characters, form a "string rule", the "rule string" is used to express a string filtering logic.

grammar

Regular expressions literally is a slash, or somewhere in between after the% r mode with any delimiter between, as follows:

/pattern/
/pattern/im    # 可以指定选项
%r!/usr/local! # 使用分隔符的正则表达式

Examples

#!/usr/bin/ruby

line1 = "Cats are smarter than dogs";
line2 = "Dogs also like meat";

if ( line1 =~ /Cats(.*)/ )
  puts "Line1 contains Cats"
end
if ( line2 =~ /Cats(.*)/ )
  puts "Line2 contains  Dogs"
end

try it"

Run the above example output is:

Line1 contains Cats

Regular expression modifiers

Regular expressions literally may contain an optional modifier for controlling various aspects of the match. Modifier after the second slash character designation, as shown in the example above. Index lists the possible modifiers:

Like strings separated by% Q Like, Ruby allows you to% r as the beginning of the regular expression, followed by an arbitrary delimiter. This description contains a large number of very useful when you do not want to escape the slash character.

# 下面匹配单个斜杠字符，不转义
%r|/|               

# Flag 字符可通过下面的语法进行匹配
%r[</(.*)>]i  

Regular expression pattern

In addition to the controlcharacters, (+ * ^ $ () [] {} |?. \), All other characters match themselves.You can control the character before placing a backslash to escape the control characters.

The following table lists the regular expression syntax Ruby available.

Examples of regular expressions

character

Character Classes

Special character classes

repeat

Non-greedy repeat

This will match the minimum number of repetition.

Grouped by parentheses

Backreferences

This match before the match had grouped again.

replace

anchor

This requires matching the specified location.

Parentheses special syntax

Search and Replace

sub and gsubsubstitution variables and theirsub!andgsub!is important when using a regular expression string method.

All of these methods are using regular expression pattern to perform search and replace operations.sub and sub!first replacement pattern ofoccurrence,gsub andgsub!replace all occurrences of pattern.

sub and gsubreturn a new string leaving the original string is not modified, andsub!andgsub!modify the strings they will call.

Here is an example:

#!/usr/bin/ruby
# -*- coding: UTF-8 -*-

phone = "138-3453-1111 #这是一个电话号码"

# 删除 Ruby 的注释
phone = phone.sub!(/#.*$/, "")   
puts "电话号码 : #{phone}"

# 移除数字以外的其他字符
phone = phone.gsub!(/\D/, "")    
puts "电话号码 : #{phone}"

try it"

Run the above example output is:

电话号码 : 138-3453-1111 
电话号码 : 13834531111

Here is another example:

#!/usr/bin/ruby
# -*- coding: UTF-8 -*-

text = "rails 是 rails,  Ruby on Rails 非常好的 Ruby 框架"

# 把所有的 "rails" 改为 "Rails"
text.gsub!("rails", "Rails")

# 把所有的单词 "Rails" 都改成首字母大写
text.gsub!(/\brails\b/, "Rails")

puts "#{text}"

try it"

Run the above example output is:

Rails 是 Rails,  Ruby on Rails 非常好的 Ruby 框架