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:
char *strstr(const char *haystack, const char *needle);
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:
- It starts searching from the beginning of the haystack.
- It compares haystack and needle character by character until a match is found or the end of haystack is reached.
- If a match is found, it returns a pointer to the first matching character.
- If no match is found, it returns NULL.
Example:
#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; }
Output:
<code>Found 'world' at position 7</code>
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