C++ strstr() Function Example | strstr() in C++

C++ strstr() is an inbuilt string handling function that is used to find the first occurrence of a substring in a given string.  It is defined in string.h header file. It is used to find the occurrence of a substring in a string. This process of matching stops at ‘\0’ and does not include it.

C++ strstr()

The strstr() method in C++ finds the first occurrence of the byte string target in the byte string pointed to by the str. The terminating null characters are not compared.

Syntax

char *strstr( const char *str_var, const char *str_var2)

The function finds the occurrence of str_var2 in str_var1 and stops where it gets the first occurrence. (It doesn’t count the null character).

Parameters

It takes two parameters. The first one, str_var is the main string from which we will search the substring. The second one is the substring (str_var2), which is to be searched in the main string(str_var).

Return Value

It returns a pointer which points to the first character of the substring (str_var2) with the index of main string(str_var) only if the substring is found. If a substring is not found, it returns a null pointer.  If the substring is found, then strstr() method returns the pointer to the first character of a substring in dest. If the substring is not found, a null pointer is returned. If the dest points to an empty string, str is returned

Example program on strstr() function in C++

Example 1: Write a program to show the working of strstr() in C++.

#include <iostream>
#include <string.h>
#include <stdio.h>

using namespace std;

int main()
{
  char str_var[] = "HelloBOYSandGIRLS";
  char str_var2[] = "BOYS";
  char *k;
  k = strstr(str_var, str_var2);
  if (k)
  {
    cout << "Main string: " << str_var << endl;
    cout << "Substring: " << str_var << endl;
    cout << "Congo! Substring is present";
  }
  else
  {
    cout << "Substring not found";
  }
  return 0;
}

Output

Main string: HelloBOYSandGIRLS	
Substring:  BOYS
Congo! Substring is present

Example 2: Write a program in which the substring points to an empty string and then print the output.

See the following code.

#include <iostream>
#include <string.h>
#include <stdio.h>

using namespace std;

int main()
{
  char str_var[] = "HelloBOYSandGIRLS";
  char str_var2[] = " ";
  char *k;
  k = strstr(str_var, str_var2);
  if (k)
  {
    cout << k;
  }
  else
  {
    cout << "Substring not found";
  }
  return 0;
}

Output

Substring not found

See also

C++ strtok()

C++ strspn()

C++ strpbrk()

C++ strcspn()

C++ strchr()