Development/Architecture/KDE4/Starting Other Programs

KDE Architecture - Starting programs

In KDE there are several ways to start other programs from within your application. Here is a short summary of your options with reasons why you should or should not use them.

fork + exec

You never want to use this unless you have a very good reason why it is impossible to use KProcess.

KProcess

You want to use KProcess class if you need to start a new process which needs to be a child of your process, e.g. because you want to catch stdout/stderr or need to send it data via stdin. You should never use this to start other KDE applications (unless your application is a debugger :-)

KToolInvocation::startServiceByDesktopPath

KToolInvocation::startServiceByDesktopPath is the preferred way to launch desktop (KDE/Gnome/X) applications or KDE services. The application/service must have a .desktop file, and you must know the name of that file. It will make use of KDEinit for increased startup performance and lower memory usage. These benefits only apply to applications available as KDEinit loadable module (KLM).

KRun

Generic way to open documents/applications/shell commands. Uses startServiceByDesktopPath where applicable. Offers the additional benefit of startup-notification.
KRun can start any application, from the binary or the desktop file, it will determine the mimetype of a file before running the preferred handler for it, and it can also start shell commands. This makes KRun the recommended way to run another program in KDE.

KToolInvocation::invokeBrowser

KToolInvocation::invokeBrowser launches a web browser. The difference with KRun is that KRun has to determine the mimetype of the URL first (which, for HTTP, involves starting a download to read the headers), so if you know that the URL is an HTML webpage, use invokeBrowser in order to skip that step and let the browser window show faster (the mimetype check is especially annoying if the user's preferred browser is a non-kde application like firefox, rather than konqueror, which can reuse the kioslave started by KRun).