Class

# IOException

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## Description

Raised when an IO error occurs in classes that perform file or stream operations, including `BinaryStream</api/files/binarystream>`, `FolderItem</api/files/folderitem>`, `PDFDocument</api/pdf/pdfdocument>`, `SerialConnection</api/hardware/serialconnection>`, `SpecialFolder</api/files/specialfolder>`, `TextInputStream</api/files/textinputstream>`, and `TextOutputStream</api/files/textoutputstream>`.

## Properties

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| Name                                   | Type                               | Read-Only | Shared |
|----------------------------------------|------------------------------------|-----------|--------|
| `ErrorNumber<ioexception.errornumber>` | `Integer</api/data_types/integer>` |           |        |
| `Message<ioexception.message>`         | `String</api/data_types/string>`   |           |        |

## Methods

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| Name                                    | Parameters                                                                                              | Returns                                    | Shared |
|-----------------------------------------|---------------------------------------------------------------------------------------------------------|--------------------------------------------|--------|
| `Constructor<ioexception.constructor0>` | message As `String</api/data_types/string>` = "", errorNumber As `Integer</api/data_types/integer>` = 0 |                                            |        |
| `Stack<ioexception.stack>`              |                                                                                                         | `String()</api/data_types/string>`         |        |
| `StackFrames<ioexception.stackframes>`  |                                                                                                         | `StackFrame()</api/exceptions/stackframe>` |        |

## Property descriptions

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IOException.ErrorNumber

**ErrorNumber** As `Integer</api/data_types/integer>`

> Used to contain an error number that describes the runtime error.

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IOException.Message

**Message** As `String</api/data_types/string>`

> Used to contain descriptive text to display when the runtime exception is encountered.

## Method descriptions

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IOException.Constructor

**Constructor**(message As `String</api/data_types/string>` = "", errorNumber As `Integer</api/data_types/integer>` = 0)

> <div class="note">
>
> <div class="title">
>
> Note
>
> </div>
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> `Constructors</api/language/constructor>` are special methods called when you create an object with the `New</api/language/new>` keyword and pass in the parameters above.
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> </div>
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> Used to raise your own `RuntimeException</api/exceptions/runtimeexception>` with a *message* and optional error number.

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IOException.Stack

**Stack** As `String()</api/data_types/string>`

> Returns a `String</api/data_types/string>` array that contains a list of all of the methods in the stack from the main entrypoint to the point at which the exception was invoked.
>
> The stack contains all the method names up and including the current method name.
>
> This feature only works if the **IncludeFunctionNames** property on the App object is selected in the Shared Build Settings.
>
> In addition to your own method calls, you will also see framework method calls, but these may not always be completely accurate due to insufficient symbols for the OS to resolve.

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IOException.StackFrames

**StackFrames** As `StackFrame()</api/exceptions/stackframe>`

> Returns an array containing the stack when the exception was first raised.

## Notes

An <span class="title-ref">IOException</span> can be raised by any class that performs file or stream operations. This includes `BinaryStream</api/files/binarystream>`, `FolderItem</api/files/folderitem>`, `PDFDocument</api/pdf/pdfdocument>`, `SerialConnection</api/hardware/serialconnection>`, `SpecialFolder</api/files/specialfolder>`, `TextInputStream</api/files/textinputstream>`, and `TextOutputStream</api/files/textoutputstream>`. Always wrap IO operations in a `Try/Catch</api/language/try>` block to handle these errors gracefully.

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### Error codes

The `ErrorNumber<runtimeexception.errornumber>` property of an <span class="title-ref">IOException</span> may be set to an OS error code.

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#### macOS

The [OS Status](https://osstatus.com) web site can help track down error code meanings.

In addition, you can use the `macerror` command in Terminal to find a description of an error.

For example:

`macerror -49` displays: `Mac OS error -49 (opWrErr): file already open with write permission`

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#### Windows

Windows error codes are available at [MSDN](http://msdn.microsoft.com/en-us/library/ms681382(VS.85).aspx).

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#### Linux

Error Codes for Linux can be found [here](https://www.thegeekstuff.com/2010/10/linux-error-codes/).

## Sample code

The following example catches an <span class="title-ref">IOException</span> if it occurs.

``` xojo
Var f As FolderItem = FolderItem.ShowSaveFileDialog(FileTypes1.Text, "Create Example.txt")

If f <> Nil Then
  Var t As TextOutputStream = TextOutputStream.Create(f)  ' this line could raise an IOException.
  t.WriteLine(TextField1.Text)
  t.Close
End If

Exception err As IOException
  MessageBox("An error occurred while attempting to create/save the file.")
```

## Compatibility

|                       |     |
|-----------------------|-----|
| **Project Types**     | All |
| **Operating Systems** | All |

<div class="seealso">

`RuntimeException</api/exceptions/runtimeexception>` parent class; `BinaryStream</api/files/binarystream>`, `TextInputStream</api/files/textinputstream>`, `TextOutputStream</api/files/textoutputstream>` classes.

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