Library Function strstr() in C++
C++ Library Function : strstr()
On this page we will discuss about library function strstr() in string class which is used in C++. The cstring header file is a C++ header file that provides functions for manipulating C-style strings. strstr() is a function in the C++ standard library that searches for the first occurrence of a substring within a string.
Library Function strstr() in C++
In C++ programming language, the strstr function is included in cstring header file.
This function takes two arguments: str1 and str2. It searches for the first occurrence of a str2 within str1 and stops on ‘\0′(null terminating character).
Declaration
char *strstr(const char *str1, const char *str2);
Parameters
The strstr function in C++ takes two parameters:
| Parameter | Description |
|---|---|
| str1 | This is the string in which to search for the substring. It is a pointer to a null-terminated string. |
| str2 | This is the string to search for within str1. It is also a pointer to a null-terminated string. |
Return value
- If str2 is found within str1, a pointer to the first occurrence of str2 within str1 is returned.
- If str2 is not found within str1, a null pointer is returned.
- If an empty string is found in str2 then str1 is returned.
Implementation of Library Function strstr() :
Example 1:
The following code shows the use of strstr() function.
#include<iostream>
#include<cstring>
using namespace std;
int main()
{
char str1[] = "PrepInsta Prime";
char str2[] = "Prime";
char *p = strstr(str1, str2);
if (p)
cout << " Found " << str2 << " in " << str1 << " at index " << p-str1;
else
cout << str2 << " Did not find " << str1 << " in ";
return 0;
}
Output:
Found Prime in PrepInsta Prime at index 10
Example 2:
The following code shows the use of strstr() function when str2 is an empty string.
#include <iostream>
#include <cstring>
using namespace std;
int main()
{
char str1[] = "PrepInsta Prime";
char str2[] = "";
char *p = strstr(str1, str2);
if (p)
cout << " Found " << str2 << " in " << str1 << " at index " << p-str1;
else
cout << str2 << " Did not find " << str1 << " in ";
return 0;
}
Output:
Found in PrepInsta Prime at index 0
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