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C - strstr() Function With Example

Here, we are going to demonstrate the strstr() function in C programming language.
Submitted by Nidhi, on July 21, 2021

C strstr() Function Definition

The strstr() function is used to find the first occurrence of a specified substring within the string and return the pointer to the calling function. It returns NULL if the substring is not found within the string.

Syntax

char *strstr(const char *str, const char *substr);

Parameters

• str - string to be searched.
• substr - substring to search for.

Return Value

This function returns a pointer to the first occurrence of the substring.

strstr() Function Example

The source code to demonstrate the strstr() function is given below. The given program is compiled and executed using GCC compile on UBUNTU 18.04 OS successfully.

// C - strstr() Function With Example

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

int main()
{
    char str[32] = "India is great country";
    char* ptr;

    ptr = strstr(str, "great");
    if (ptr != NULL)
        printf("String is: '%s'\n", ptr);
    else
        printf("Word 'great' is not found\n");

    ptr = strstr(str, "power");
    if (ptr != NULL)
        printf("String is: %s\n", ptr);
    else
        printf("Word 'power' is not found\n");

    return 0;
}

Output

String is: 'great country'
Word 'power' is not found

Explanation

In the main() function, we created a string str initialized with "India is great country". Then we used the strstr() function to find the specified substring "reat" within the string. The strstr() function is used to find the first occurrence of a specified substring within the string and returns the pointer to the calling function. It returns NULL if the substring is not found within the string.

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