# SDL_strcasestr

Search a UTF-8 string for the first instance of a specific substring, case-insensitively.

## Header File

Defined in [<SDL3/SDL_stdinc.h>](https://github.com/libsdl-org/SDL/blob/main/include/SDL3/SDL_stdinc.h)

## Syntax

```c
char * SDL_strcasestr(const char *haystack, const char *needle);
```

## Function Parameters

|              |              |                                             |
| ------------ | ------------ | ------------------------------------------- |
| const char * | **haystack** | the string to search. Must not be NULL.     |
| const char * | **needle**   | the string to search for. Must not be NULL. |

## Return Value

(char *) Returns a pointer to the first instance of `needle` in the string,
or NULL if not found.

## Remarks

This will work with Unicode strings, using a technique called
"case-folding" to handle the vast majority of case-sensitive human
languages regardless of system locale. It can deal with expanding values: a
German Eszett character can compare against two ASCII 's' chars and be
considered a match, for example. A notable exception: it does not handle
the Turkish 'i' character; human language is complicated!

Since this handles Unicode, it expects the strings to be well-formed UTF-8
and not a null-terminated string of arbitrary bytes. Bytes that are not
valid UTF-8 are treated as Unicode character U+FFFD (REPLACEMENT
CHARACTER), which is to say two strings of random bits may turn out to
match if they convert to the same amount of replacement characters.

## Thread Safety

It is safe to call this function from any thread.

## Version

This function is available since SDL 3.2.0.

----
[CategoryAPI](CategoryAPI), [CategoryAPIFunction](CategoryAPIFunction), [CategoryStdinc](CategoryStdinc)

