C++ || How To Execute & Get Regex Match Results Using C++

December 11, 2020 admin No comments

The following is a module with functions which demonstrates how to execute and get regex match results using C++.

The function demonstrated on this page uses regex to search a specified input string for all occurrences of a specified regular expression. The function returns a collection of std::smatch objects found by the search.

1. Get Regex Matches

The example below demonstrates the use of ‘Utils::getRegexMatches‘ to search an input string for all occurrences of a regular expression.





		
		
			1. Get Regex Matches
			
C++
			
			// Get Regex Matches

// Declare source 
std::string input = "Kenneth, Jennifer, Lynn, Sole";

// Declare pattern
std::string pattern = R"(\w+)";

// Find matches
auto matches = Utils::getRegexMatches(pattern, input);

// Display results
for (const auto& match : matches) {
    // Display full match
    std::cout << "Match: " << match.str() << std::endl;
}

// example output:
/*
    Match: Kenneth
    Match: Jennifer
    Match: Lynn
    Match: Sole
*/
			
				
					
				
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						// Get Regex Matches
 
// Declare source 
std::string input = "Kenneth, Jennifer, Lynn, Sole";
 
// Declare pattern
std::string pattern = R"(\w+)";
 
// Find matches
auto matches = Utils::getRegexMatches(pattern, input);
 
// Display results
for (const auto& match : matches) {
    // Display full match
    std::cout << "Match: " << match.str() << std::endl;
}
 
// example output:
/*
    Match: Kenneth
    Match: Jennifer
    Match: Lynn
    Match: Sole
*/

2. Get Regex Matches – Sub Match

The example below demonstrates the use of ‘Utils::getRegexMatches‘ to search an input string for all occurrences of a regular expression.

In this example, sub matches are expected and displayed.





		
		
			2. Get Regex Matches - Sub Match
			
C++
			
			// Get Regex Matches - Sub Match

// Declare source 
std::string input = "212-555-6666 906-932-1111 415-222-3333 425-888-9999";

// Declare pattern
std::string pattern = R"((\d{3})-(\d{3}-\d{4}))";

// Find matches
auto matches = Utils::getRegexMatches(pattern, input);

// Display results
for (const auto& match : matches) {
    // Display full match
    std::cout << "Full Match: " << match.str() << std::endl;

    // Display any submatches
    for (unsigned index = 1; index < match.size(); ++index) {
        std::cout << "  Sub Match #" << index 
            << ": " << match.str(index) << std::endl;
    }
}

// example output:
/*
    Full Match: 212-555-6666
      Sub Match #1: 212
      Sub Match #2: 555-6666
    Full Match: 906-932-1111
      Sub Match #1: 906
      Sub Match #2: 932-1111
    Full Match: 415-222-3333
      Sub Match #1: 415
      Sub Match #2: 222-3333
    Full Match: 425-888-9999
      Sub Match #1: 425
      Sub Match #2: 888-9999
*/
			
				
					
				
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						// Get Regex Matches - Sub Match
 
// Declare source 
std::string input = "212-555-6666 906-932-1111 415-222-3333 425-888-9999";
 
// Declare pattern
std::string pattern = R"((\d{3})-(\d{3}-\d{4}))";
 
// Find matches
auto matches = Utils::getRegexMatches(pattern, input);
 
// Display results
for (const auto& match : matches) {
    // Display full match
    std::cout << "Full Match: " << match.str() << std::endl;
 
    // Display any submatches
    for (unsigned index = 1; index < match.size(); ++index) {
        std::cout << "  Sub Match #" << index 
            << ": " << match.str(index) << std::endl;
    }
}
 
// example output:
/*
    Full Match: 212-555-6666
      Sub Match #1: 212
      Sub Match #2: 555-6666
    Full Match: 906-932-1111
      Sub Match #1: 906
      Sub Match #2: 932-1111
    Full Match: 415-222-3333
      Sub Match #1: 415
      Sub Match #2: 222-3333
    Full Match: 425-888-9999
      Sub Match #1: 425
      Sub Match #2: 888-9999
*/

3. Utils Namespace

The following is the Utils Namespace. Include this in your project to start using!





		
		
			Utils Namespace
			
C++
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 11, 2020
//    Taken From: http://programmingnotes.org/
//    File:  Utils.h
//    Description: Handles general utility functions
// ============================================================================
#pragma once
#include <regex>
#include <vector>

namespace Utils {
    /**
    * FUNCTION: getRegexMatches 
    * USE: Searches the specified input string for all occurrences of a 
    *   specified regular expression
    * @param pattern: The regular expression pattern to match
    * @param input: The string to search for a match
    * @return: A collection of std::smatch objects found by the search. If 
    *   no matches are found, the method returns an empty collection
    */
    auto getRegexMatches(const std::string& pattern, const std::string& input) {
        std::vector<std::smatch> results;
        std::regex rgx(pattern);
        for (std::sregex_iterator it(input.begin(), input.end(), rgx), end; it != end; ++it) {
            results.push_back(*it);
        }
        return results;
    }
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 11, 2020
//    Taken From: http://programmingnotes.org/
//    File:  Utils.h
//    Description: Handles general utility functions
// ============================================================================
#pragma once
#include <regex>
#include <vector>
 
namespace Utils {
    /**
    * FUNCTION: getRegexMatches 
    * USE: Searches the specified input string for all occurrences of a 
    *   specified regular expression
    * @param pattern: The regular expression pattern to match
    * @param input: The string to search for a match
    * @return: A collection of std::smatch objects found by the search. If 
    *   no matches are found, the method returns an empty collection
    */
    auto getRegexMatches(const std::string& pattern, const std::string& input) {
        std::vector<std::smatch> results;
        std::regex rgx(pattern);
        for (std::sregex_iterator it(input.begin(), input.end(), rgx), end; it != end; ++it) {
            results.push_back(*it);
        }
        return results;
    }
}// http://programmingnotes.org/

4. More Examples

Below are more examples demonstrating the use of the ‘Utils‘ Namespace. Don’t forget to include the module when running the examples!





		
		
			More Examples
			
C++
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 11, 2020
//    Taken From: http://programmingnotes.org/
//    File:  program.cpp
//    Description: The following demonstrates the use of the Utils Namespace
// ============================================================================
#include <iostream>
#include <string>
#include <exception>
#include "Utils.h"

void display(const std::string& message);

int main() {
    try {
        // Declare source 
        std::string input = "Kenneth, Jennifer, Lynn, Sole";
        // input = "212-555-6666 906-932-1111 415-222-3333 425-888-9999";

        // Declare pattern
        std::string pattern = R"(\w+)";
        // pattern = R"((\d{3})-(\d{3}-\d{4}))";

        // Find matches
        auto matches = Utils::getRegexMatches(pattern, input);

        // Display results
        for (const auto& match : matches) {
            // Display full match
            std::cout << "Full Match: " << match.str() << std::endl;

            // Display any submatches
            for (unsigned index = 1; index < match.size(); ++index) {
                std::cout << "  Sub Match #" << index 
                    << ": " << match.str(index) << std::endl;
            }
        }
    } catch (std::exception& e) {
        display("\nAn error occurred: " + std::string(e.what()));
    }

    std::cin.get();
    return 0;
}

void display(const std::string& message) {
    std::cout << message << std::endl;
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Dec 11, 2020
//    Taken From: http://programmingnotes.org/
//    File:  program.cpp
//    Description: The following demonstrates the use of the Utils Namespace
// ============================================================================
#include <iostream>
#include <string>
#include <exception>
#include "Utils.h"
 
void display(const std::string& message);
 
int main() {
    try {
        // Declare source 
        std::string input = "Kenneth, Jennifer, Lynn, Sole";
        // input = "212-555-6666 906-932-1111 415-222-3333 425-888-9999";
 
        // Declare pattern
        std::string pattern = R"(\w+)";
        // pattern = R"((\d{3})-(\d{3}-\d{4}))";
 
        // Find matches
        auto matches = Utils::getRegexMatches(pattern, input);
 
        // Display results
        for (const auto& match : matches) {
            // Display full match
            std::cout << "Full Match: " << match.str() << std::endl;
 
            // Display any submatches
            for (unsigned index = 1; index < match.size(); ++index) {
                std::cout << "  Sub Match #" << index 
                    << ": " << match.str(index) << std::endl;
            }
        }
    } catch (std::exception& e) {
        display("\nAn error occurred: " + std::string(e.what()));
    }
 
    std::cin.get();
    return 0;
}
 
void display(const std::string& message) {
    std::cout << message << std::endl;
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

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Posted in: Advanced, C++ Tags: c++, regex

C++ || How To Execute & Get Regex Match Results Using C++

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