Regular Expression
Most of Ruby's built-in types and otherProgramming LanguageVery similar. Mainly include strings, integers, floats, and arrays. However, only the script language,
Such as Ruby, Perl, and awk provide support for built-in expression types. It is a powerful text processing tool, though the
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The odd words used together in those patterns are called regular expressions. Like Perl, Ruby uses a front slash, not a double quote, to enclose them. If you've never used regular expressions before, maybe they seem to be nothing but rules (regular). But it's wise to spend a little time understanding them. When y
expressions. like Perl, Ruby also uses forward slashes (instead of double quotation marks) to enclose them. if you have never used regular expressions before, maybe they seem to be nothing except Rules (regular), but it is wise to spend a little time learning about them. when you need to perform pattern matching, search, or other operations on strings, its effic
A regular expression is a special sequence of characters that matches or finds a collection of other strings or strings by using a pattern that has a specialized syntax.Grammar
A regular expression is literally a pattern between a slash or between any delimiter that follows a%r, as follows:
/pattern/
/pattern/
Literal constructor for Ruby regular expression:
//Try this:
>>//.class=> RegexpPattern matching consists of two parts, a regular expression (regexp), and a string. A regular expression
Regular expressions are a special sequence of characters that can help match or find other strings or string sets, using patterns that maintain a specialized syntax.
The regular expression literal is a pattern between a slash or any delimiter%r as follows:Grammar:
Copy Code code as follows:
/pattern/
/PATTERN/IM # option can be specified
%r!/
Most of Ruby's built-in types are similar to other programming languages. Mainly have strings,integers,floats,arrays and so on. However, only the scripting language,
such as Ruby,perl, and awk provide support for built-in expression types. Shame: Regular expressions are a powerful text-processing tool, albeit covert.
They are very different than simply adding a
Perl, Ruby also uses forward slashes (instead of double quotation marks) to enclose them. if you have never used regular expressions before, maybe they seem to be nothing except Rules (regular), but it is wise to spend a little time learning about them. when you need to perform pattern matching, search, or other operations on strings, its efficient
Speaking of Ruby, of course, we need to mention its regular expression mechanism. As a powerful matching language, regular expressions are increasingly used in different fields, from string verification, matching, to web page extraction. Although some people criticize the matching efficiency with
Regular Expression
Regular Expressions are applicable in many scenarios. For example, verify whether the string matches the format, find the matched string, and replace the matched string.
Many programming languages support regular expressions with similar syntax.
A regular
In the PP file for writing puppet, many of the regular expressions for Ruby are used and are commonly used as follows:
Regular expression:
[Codesyntax lang= "Ruby"]
{}: The number of repetitions (such as {4} indicates that the preceding repeat occurs exactly 4 time
Tutorial on the basic usage of Regular Expressions in Ruby programs, ruby Regular Expressions
Most of Ruby's built-in types are similar to other programming languages. Mainly include strings, integers, floats, and arrays. However, only script languages such as Ruby, Perl, an
Detailed description of matching and replacement operations on strings by regular expressions in Ruby, and ruby Regular Expressions
Regular Expression matching
Speaking of Ruby, of cour
Basic instructions for using regular expressions in Ruby, ruby Regular Expressions
Built-in support for regular expressions is usually limited to scripting languages such as Ruby, Perl, and awk. This is a shame: although
This section describes the regular expressions and Ruby Regular Expressions in ruby.
A regular expression is a character of a special sequence. It matches or searches for other strings or string sets by using a pattern with specia
An example is provided to explain the regular expressions in Ruby and the regular expressions in ruby.
A regular expression is a special character sequence that can help match or find other strings or strings. The pattern used mai
finite automatonDeterministic Finite Automaton
DFA engines do not require backtracking (and therefore they never test the same character twice), So matchFast! The DFA engine can also match the longest possible string. However, the DFA engine only contains a limited number of States, so it cannot match a pattern with a reverse reference.Subexpressions cannot be captured.. Representativeness:Awk, egrep, flex, lex, MySQL, Procmail
NFA Non-deterministic finite automatic Non-determin
DFA engine they do not require backtracking (and therefore they never test the same characters two times), so the match is fast ! The DFA engine can also match the longest possible string. However, the DFA engine contains only a limited state, so it cannot match a pattern with a reverse reference, and no subexpression can be captured . Representative: awk,egrep,flex,lex,mysql,procmail
NFA non-deterministic Finite automaton is a finite automaton, and is divided into tra
$string='April15,2003';$pattern='/(\w+)(\d+),(\d+)/i';$replacement='${1},${3}';echo preg_replace($pattern,$replacement,$string);?>
The result of this expression is april1,2003Cause: (\w+) can match April15 completely, but because (\d+) is behind (\w+), in order to be able to match defined rules, (\w+) matches April1, (\d+) matches 5You can change the expression to avoid this situation such as:$pattern = '/
Regular expression is regular expression, it seems that English is better than Chinese understand more, is to check expression characters
Not meet the rules!! Regular expressions have a very powerful and very complex object regexp
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