frame-title-format

frame-title-format is a variable defined in `C source code'.
Its value is

(multiple-frames "%b"
		 ("" invocation-name "@" system-name))

• This variable may be risky if used as a file-local variable.

Documentation:
Template for displaying the title bar of visible frames.
(Assuming the window manager supports this feature.)

This variable has the same structure as `mode-line-format', except that
the %c and %l constructs are ignored. It is used only on frames for
which no explicit name has been set (see `modify-frame-parameters').