C Reference String Operation: strstr()

The function strstr() returns a pointer to the first occurrence of x in a string.
It is also know as searching for a sub-string in a string.

Usage:

char * strstr ( const char *, const char * );
char * strstr ( char * str1, const char * str2 );

Return Value

A pointer to the first occurrence in str1 of any of the entire sequence of characters specified in str2. If nothing is found a null pointer is returned if the sequence is not present in str1.

strstr() source code example:

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

int main ()
{
  char a[] ="Just some random string";
  char * ptr_b;
  ptr_b = strstr (a,"string");
  printf("%s\n",ptr_b);
  ptr_b = strstr (a,"wrong");
  printf("%s",ptr_b);
  return 0;
}

Output of the example:

	string
	(null)

Note: the first output the word string because the word is found, the second word isn’t found that’s why null is returned.