# fsIOOpenRead<no value>
The **fsIOOpenRead** function is used to open a file and read data from it.

 

##### Syntax

``` wasm
FsIOFile fsIOOpenRead(
    const char* path,
    FsIOOpenFlags flags,
    char* outBuffer,
    int byteOffset,
    int byteToRead,
    FsIOFileReadCallback callback,
    void* pUserData
);
```

 

##### Members

<table><thead><tr class="header"><th>Parameters</th><th>Description</th></tr></thead><tbody><tr class="odd"><td><code>path</code></td><td><p>Path to the file being opened for reading. Files must exist within the package using the module to be able to be read, however please note that some files may be encrypted or inaccessible, as explained here: <a href="IO_API/#inaccessible">Inaccessible Files</a></p><p>You can use the following to target files from the package folder root or the persistent storage root:</p><ol><li><p><code>./</code> - to access the files from within the add-on package, eg:</p><pre class="language-wasm"><code>./data/pi.txt</code></pre><p>The above path will look for the <code>pi.txt</code> file in the data folder from the <strong>package root in the VFS</strong>.</p></li></ol><ol><li><p><code>/work/</code> - to access a persistent storage that the add-on can use, eg:</p><pre class="language-wasm"><code>/work/pi.txt</code></pre><p>The path above will look in the <strong>persistent storage</strong> folder for the <code>pi.txt</code> file. This file is located here:  

<code>%appdata%/Microsoft Flight Simulator/WASM/MSFS2020/PackageName/work</code></p></li></ol></td></tr><tr class="even"><td><code>flags</code></td><td>This is a bit-flag defining how the file should be opened. Please see <code>FsIOOpenFlags</code> for details.</td></tr><tr class="odd"><td><code>outBuffer</code></td><td>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 <code>byteToRead</code> bytes (if not set to -1).</td></tr><tr class="even"><td><code>byteOffset</code></td><td>This is the offset into the file from which data will be read. If this is not <code>null</code> then <code>byteToRead</code> must <em>not</em> be set to -1.</td></tr><tr class="odd"><td><code>byteToRead</code></td><td>This defines the number of bytes to read from the file. If set to -1, the entire file will be read.</td></tr><tr class="even"><td><code>callback</code></td><td>Callback (<code>FsIOFileReadCallback</code>) that is sent when the open operation is finished.</td></tr><tr class="odd"><td><code>pUserData</code></td><td>Pointer given to the callback to identify the function call.</td></tr></tbody></table>

 

##### Return Values

An ID pointer representing the file being opened.

 

##### Remarks

This function is non-blocking: it will not wait for the file to be opened to pass to the next line of code. Errors can be checked for using the `fsIOGetLastError` function.