[CALUG] %d, %f, %s?

[John Cunningham]

I notice from creating desktop launchers in Gnome and Xfce that I can
specify that a program work with a particular file by sticking "%f" at
the end of the command.  I learned by trial and error that I can get
it to work on a directory by using "%d".  In .mailcap I can tell a
program to use data from stdin by sticking %s after the command.  What
is this notation called, and where is it documented?

Thanks,

John