std::regex_match, std::regex_replace() | Regex (Regular Expression) In C++
Last Updated :
04 Jul, 2022
Regex is the short form for “Regular expression”, which is often used in this way in programming languages and many different libraries. It is supported in C++11 onward compilers.
Function Templates used in regex
regex_match() -This function return true if the regular expression is a match against the given string otherwise it returns false.
CPP
#include <iostream>
#include <regex>
using namespace std;
int main()
{
string a = "GeeksForGeeks" ;
regex b( "(Geek)(.*)" );
if ( regex_match(a, b) )
cout << "String 'a' matches regular expression 'b' \n" ;
if ( regex_match(a.begin(), a.end(), b) )
cout << "String 'a' matches with regular expression "
"'b' in the range from 0 to string end\n" ;
return 0;
}
|
Output
String 'a' matches regular expression 'b'
String 'a' matches with regular expression 'b' in the range from 0 to string end
regex_search() – This function is used to search for a pattern matching the regular expression
CPP
#include <iostream>
#include <regex>
#include<string.h>
using namespace std;
int main()
{
string s = "I am looking for GeeksForGeeks "
"articles" ;
regex r( "Geek[a-zA-Z]+" );
smatch m;
regex_search(s, m, r);
for ( auto x : m)
cout << x << " " ;
return 0;
}
|
regex_replace() This function is used to replace the pattern matching to the regular expression with a string.
CPP
#include <iostream>
#include <string>
#include <regex>
#include <iterator>
using namespace std;
int main()
{
string s = "I am looking for GeeksForGeek \n" ;
regex r( "Geek[a-zA-z]+" );
cout << std::regex_replace(s, r, "geek" );
string result;
regex_replace(back_inserter(result), s.begin(), s.end(),
r, "geek" );
cout << result;
return 0;
}
|
Output
I am looking for geek
I am looking for geek
So Regex operations make use of following parameters :
- Target sequence (subject) – The string to be matched.
- Regular Expression (Pattern) – The regular expression for the target sequence.
- Matched Array – The information about matches is stored in a special match_result array.
- Replacement String – These string are used for allowing replacement of the matches.
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