The power of built-in variables

What are built-in variables?

As the name says, built-in variables are built-in. Their content is not filled by the user but by AutoHotkey itself. There are several differences with their handling:

• built-in variables are available everywhere, in the auto-execute section, any label and any user-defined function
• the content of a built-in variable can not be changed directly by the user (some exceptions listed below)
• all built-in variables begin with an A_ prefix, except for ErrorLevel, ComSpec and ProgramFiles (which is also available as A_ProgramFiles)

Note: In AutoHotkey v2 and AutoHotkey_H v2, the ComSpec and ProgramFiles variables are removed (and A_ComSpec is introduced).

Setting the content

As noted above, you usually can’t change the content of a built-in variable. There are 2 exceptions of that rule:

• ErrorLevel can be set
• IronAHK uses built-in variable assignment to replace some commands such as SetWorkingDir C:\Any\Dir by A_WorkingDir := "C:\Any\Dir"

Which variables are available?

There are way too much built-in variables to list them all here. The areas they cover reach from A_Space over script properties, date & time, script settings, user idle time, GUI variables, OS info up to things like A_LastHotkey.

A list of them can be found in the respective manual. Online links:

• AutoHotkey classic
• AutoHotkey_L

booleans

Additionally to those listed in the links above, AutoHotkey has the built-in variables (or constants) true and false. IronAHK also introduces null.