Usage of strstr function in c language

The strstr() function searches a string for a substring, returning a pointer to the first matching substring or NULL (not found). The usage steps are as follows: 1. Search from the beginning of the string; 2. Compare character by character to find a match or reach the end of the string; 3. Return the matching character pointer if found, or NULL if not found.

Usage of strstr function in C language

The strstr function is used to find subcharacters in a string Standard C function for strings. It returns a pointer to the first matching substring, or NULL if no match is found.

Syntax:

<code class="c">char *strstr(const char *haystack, const char *needle);</code>

Parameters:

• haystack: Characters to search for string.
• needle: The substring to find.

Return value:

• If needle is found in haystack, a pointer to the first character of needle is returned.
• If needle is an empty string, return haystack.
• If needle is not found in haystack, NULL is returned.

Usage:

The strstr function works as follows:

1. It starts searching from the beginning of the haystack.
2. It compares haystack and needle character by character until a match is found or the end of haystack is reached.
3. If a match is found, it returns a pointer to the first matching character.
4. If no match is found, it returns NULL.

Example:

<code class="c">#include <stdio.h>
#include <string.h>

int main() {
  char haystack[] = "Hello, world!";
  char needle[] = "world";

  char *result = strstr(haystack, needle);

  if (result) {
    printf("Found '%s' at position %ld\n", needle, result - haystack);
  } else {
    printf("'%s' not found in '%s'\n", needle, haystack);
  }

  return 0;
}</code>

Output:

<code>Found 'world' at position 7</code>

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