On startup, SWI-Prolog reads both site initialisation and personal initialisation files. Both can be controlled explicitly using commandline options (-F base for site, and -f base for personal initialisation).

The site-initialisation file is located in the SWI-Prolog home directory. Its name is deduced from the commandname by taking the leading alphanumerical characters, followed by the extension .rc. Using default installation this implies swipl.rc for the Unix version and swipl-win.rc for the Windows GUI version.

If XPCE is installed, it is activated through the above named system default file.

The personal initialisation file depends on version and OS:

• 8.1 and later
  The file is called init.pl and resides in a directory swi-prolog below the the XDG config home. On Unix the default XDG config home is ~/.config. On Windows it is the directory provided by win_folder/2 on appdata.

  These files are available using the file_search_path/2 alias user_app_config as well as the deprecated aliases user_profile and app_preferences

• Up to 8.0
  The file is named .swiplrc on Unix (.plrc for really old versions) and swipl.ini on Windows (pl.ini for really old versions). The file resides in the user's home (Unix) or in the appdata directory (Windows).

  These files are available using the file_search_path/2 alias user_profile.

In plwin.exe, the personal initialisation file is accessible through the Settings menu. On first use, it copies a default file with some commented commonly used customization options. The same behaviour is also available from the PceEmacs menu Edit/Prolog preferences.

The -s file command line option is often used on Unix systems to load and start applications using a single command. This option can also be used to create PrologScript files. Recent versions interpret a *.pl file on the command line as a source file. When used in a terminal, a session is typically started as

swipl file.pl