Unix in a Nutshell, 4th Edition

Internal Macros

$?	The list of prerequisites that have been changed more recently than the current target. Can be used only in normal makefile entries—not suffix rules.
$@	The name of the current target, except in makefile entries for making libraries, where it becomes the library name. (For libguide.a(dontpanic.o), $@ is libguide.a). Can be used both in normal makefile entries and in suffix rules.
$$@	The name of the current target. Can be used only to the right of the colon in dependency lines. This is provided only for compatibility with System V make; its use is not recommended.
$<	The name of the current prerequisite that has been modified more recently than the current target.
$*	The name—without the suffix—of the current prerequisite that has been modified more recently than the current target. Should be used only in implicit rules or static pattern rules.
$%	The name of the corresponding .o file when the current target is a library module. (For libguide.a(dontpanic.o), $% is dontpanic.o). Can be used both in normal makefile entries and in suffix rules.
$^	The list of prerequisites for the current target. For archive members, only the member name is listed. Even if a prerequisite appears multiple times in a dependency list for a target, it only appears once in the value of $^.
$+	Like $^, but prerequisites that appear multiple times in a dependency list for a target are repeated. This is most useful for libraries, since multiple dependencies ...