###### (This is the documentation for SDL3, which is under heavy development and the API is changing! [SDL2](https://wiki.libsdl.org/SDL2/) is the current stable version!)
# SDL_RWwrite

Write to an [SDL_RWops](SDL_RWops) data stream.

## Syntax

```c
size_t SDL_RWwrite(SDL_RWops *context, const void *ptr, size_t size);

```

## Function Parameters

|                 |                                                  |
| --------------- | ------------------------------------------------ |
| **context**     | a pointer to an [SDL_RWops](SDL_RWops) structure |
| **ptr**         | a pointer to a buffer containing data to write   |
| **size**        | the number of bytes to write                     |

## Return Value

Returns the number of bytes written, which will be less than `num` on
error; call [SDL_GetError](SDL_GetError)() for more information.

## Remarks

This function writes exactly `size` bytes from the area pointed at by `ptr`
to the stream. If this fails for any reason, it'll return less than `size`
to demonstrate how far the write progressed. On success, it returns `num`.

On error, this function still attempts to write as much as possible, so it
might return a positive value less than the requested write size. If the
function failed to write anything and there was an actual error, it will
return -1. For streams that support non-blocking operation, if nothing was
written because it would require blocking, this function returns -2 to
distinguish that this is not an error and the caller can try again later.

[SDL_RWwrite](SDL_RWwrite) is actually a function wrapper that calls the
[SDL_RWops](SDL_RWops)'s `write` method appropriately, to simplify
application development.

It is an error to specify a negative `size`, but this parameter is signed
so you definitely cannot overflow the return value on a successful run with
enormous amounts of data.

## Version

This function is available since SDL 3.0.0.

## Code Examples

```c++
SDL_RWops *rw = SDL_RWFromFile("hello.txt", "w");
if(rw != NULL) {
    const char *str = "Hello World";
    size_t len = SDL_strlen(str);
    if (SDL_RWwrite(rw, str, 1, len) != len) {
        printf("Couldn't fully write string\n");
    } else {
        printf("Wrote %d 1-byte blocks\n", len);
    }
    SDL_RWclose(rw);
}
```

## Related Functions

* [SDL_RWclose](SDL_RWclose)
* [SDL_RWFromConstMem](SDL_RWFromConstMem)
* [SDL_RWFromFile](SDL_RWFromFile)
* [SDL_RWFromMem](SDL_RWFromMem)
* [SDL_RWprint](SDL_RWprint)
* [SDL_RWread](SDL_RWread)
* [SDL_RWseek](SDL_RWseek)

----
[CategoryAPI](CategoryAPI), [CategoryIO](CategoryIO)