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# Single Application

## Description

The QtSingleApplication component provides support for applications that can be only started once per user.

For some applications it is useful or even critical that they are started only once by any user. Future attempts to start the application should activate any already running instance, and possibly perform requested actions, e.g. loading a file, in that instance.

The QtSingleApplication class provides an interface to detect a running instance, and to send command strings to that instance. For console (non-GUI) applications, the QtSingleCoreApplication variant is provided, which avoids dependency on QtGui.

## Classes

- QtSingleApplication
- QtSingleCoreApplication

## Examples

- A Trivial Example
- Loading Documents
- A Non-GUI Example

## Tested platforms

- Qt 4.4, 4.5 / Windows XP / MSVC.NET 2005
- Qt 4.4, 4.5 / Linux / gcc
- Qt 4.4, 4.5 / MacOS X 10.5 / gcc