C++ code for regular expression matching

In this blog, we will create a program for regular expression matching in C++ programming language.

What is Regular expression?

A regular expression or regular expressions or regular expressions as they are commonly called are used to represent a particular pattern of string or text. Regexes are often used to indicate the standard text syntax of a string.

Algorithm for the code

The function that is regex_match() template is used to match the given pattern. This function returns true if the given expression matches a string. Otherwise, the function returns false.

C++ code for the respective program

#include <iostream>
#include <string>
#include <regex>
using namespace std;
int main () {
   if (regex_match ("softwareTesting", regex("(soft)(.*)") ))
      cout << "string:literal => matched\n";
   const char mystr[] = "SoftwareTestingHelp";
   string str ("software");
   regex str_expr ("(soft)(.*)");
   if (regex_match (str,str_expr))
      cout << "string:object => matched\n";
   if ( regex_match ( str.begin(), str.end(), str_expr ) )
      cout << "string:range(begin-end)=> matched\n";
   cmatch cm;
   regex_match (mystr,cm,str_expr);
   smatch sm;
   regex_match (str,sm,str_expr);
   regex_match ( str.cbegin(), str.cend(), sm, str_expr);
   cout << "String:range, size:" << sm.size() << " matches\n";
   regex_match ( mystr, cm, str_expr, regex_constants::match_default );
   cout << "the matches are: ";
   for (unsigned i=0; i<sm.size(); ++i) {
      cout << "[" << sm[i] << "] ";
   cout << endl;
   return 0;

Output of the above code

 Explanation of the code

In the above program, we first compare the string “softwareTesting” with the regular expression “(“(soft)(.*)” using the regex_match function. Then we also demonstrate the different variations of regex_match by passing it a string object, range, etc.