char regex_filename[] = “[a-zA-Z_] [a-zA-Z_0-9]*\\.[a-zA-Z0-9]+”;

#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;  //匹配的詞語檢索出來
   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;
}

#include <iostream> 
#include <regex> 
#include<string.h> 
using namespace std; 
   
int main() 
{ 
    //string to be searched
    string mystr = "She sells_sea shells in the sea shore"; 
   
    // regex expression for pattern to be searched 
    regex regexp("s[a-z_]+"); 
   
    // flag type for determining the matching behavior (in this case on string objects)
     smatch m; 
   
    // regex_search that searches pattern regexp in the string mystr  
    regex_search(mystr, m, regexp); 
  
    cout<<"String that matches the pattern:"<<endl;
    for (auto x : m) 
        cout << x << " "; 
    return 0; 
}

#include <iostream> 
#include <string> 
#include <regex> 
#include <iterator> 
using namespace std; 
   
int main() 
{  
    string mystr = "This is software testing Help portal \n"; 
     
    cout<<"Input string: "<<mystr<<endl;
       
    // regex to match string beginning with 'p' 
    regex regexp("p[a-zA-z]+"); 
    cout<<"Replace the word 'portal' with word 'website' : "; 
    // regex_replace() for replacing the match with the word 'website'  
    cout << regex_replace(mystr, regexp, "website"); 
     
    string result; 
       
    cout<<"Replace the word 'website' back to 'portal': ";
    // regex_replace( ) for replacing the match back with 'portal' 
    regex_replace(back_inserter(result), mystr.begin(), mystr.end(), 
                  regexp,  "portal"); 
   
    cout << result; 
   
    return 0; 
}

#include <iostream>
#include <regex>
#include <string>
using namespace std;
  
int main()
{
    string input;
    regex integer_expr("(\\+|-)?[[:digit:]]+");
    //As long as the input is correct ask for another number
    while(true)
    {
        cout<<"Enter the input: ";
        cin>>input;
        if(!cin) break;
        //Exit when the user inputs q
        if(input=="q")
            break;
        if(regex_match(input,integer_expr))
            cout<<"Input is an integer"<<endl;
        else
        {cout<<"Invalid input : Not an integer"<<endl;}
    }
}