YouTipC Function Strstr
# C Library Function - strstr()
[ C Standard Library - ](#)
## Description
The C library function **char *strstr(const char *haystack, const char *needle)** finds the first occurrence of the string **needle** in the string **haystack**, not including the terminating null character ().
strstr() is a string handling function in the C standard library used to find the first occurrence of a substring within a string.
## Declaration
Below is the declaration for the strstr() function.
char *strstr(const char *haystack, const char *needle);
The strstr() function is used to find the first occurrence of the substring needle in the string haystack. If found, it returns a pointer to that location; if not found, it returns NULL.
## Parameters
* **haystack** -- The main string to be searched.
* **needle** -- The substring to be searched for.
## Return Value
Returns a pointer to the first occurrence of needle in haystack. If needle is not found in haystack, NULL is returned.
## Example
The following example demonstrates the usage of the strstr() function.
## Example 1
#include#includeint main(){const char haystack = "TUTORIAL"; const char needle = "NOOB"; char *ret; ret = strstr(haystack, needle); printf("Substring is: %sn", ret); return(0); }
Let us compile and run the above program, this will produce the following result:
Substring is: NOOB
## Example 2
#include
#include
int main(){
const char*haystack ="Hello, world! This is a test string.";
const char*needle ="world";
// Find needle in haystack
char*result =strstr(haystack, needle);
if(result != NULL){
printf("Substring found: %sn", result);
}else{
printf("Substring not found.n");
}
return 0;
}
**Code Explanation:**
* The `strstr()` function starts searching for `needle` from the beginning of `haystack` until a match is found or the end of `haystack` is reached.
* If `needle` is an empty string (`""`), `strstr()` returns the starting address of `haystack`.
* `strstr()` is case-sensitive. If a case-insensitive search is needed, you can use `strcasestr()` (a non-standard function that may require specific library support).
Output:
Substring found: world! This is a test string.
[ C Standard Library - ](#)