# fsIORead<no value>
The **fsIORead** function is used to read data from a file.

 

##### Syntax

``` wasm
FsIOErr fsIORead(
    FsIOFile file,
    char* outBuffer,
    int byteOffset,
    int byteToRead,
    FsIOFileReadCallback callback,
    void* pUserData
);
```

 

##### Members

{{< table-wrapper >}}

| Parameters   | Description                                                                                                                                                                                                       |
|--------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `file`       | This is the ID of a previously opened file, as returned by the `fsIOOpen` function.                                                                                                                               |
| `outBuffer`  | This is a pointer to a previously created buffer which will store the data being read. It needs to be allocated and must be large enough to contains the whole file or the `byteToRead` bytes (if not set to -1). |
| `byteOffset` | This is the offset into the file from which data will be read. If this is not `null` then `byteToRead` must *not* be set to -1.                                                                                   |
| `byteToRead` | This defines the number of bytes to read from the file. If set to -1, the entire file will be read.                                                                                                               |
| `callback`   | Callback (`FsIOFileReadCallback`) that is sent when the read operation is finished.                                                                                                                               |
| `pUserData`  | Pointer given to the callback to identify the function call.                                                                                                                                                      |

{{< /table-wrapper >}}


 

##### Return Values

The function returns one of the `FsIOErr` codes.

 

##### Remarks

This function is non-blocking: it will not wait for the file to be read to pass to the next line of code.