$@ | The file name of the target of the rule |
$% | The target member name, when the target is an archive member |
$< | The name of the first prerequisite |
$? | The names of all the prerequisites that are newer than the target |
$^ | The names of all the prerequisites with spaces between them |
$+ | Similar to '$^', but prerequisites listed more than once are duplicated in the order they were listed in the makefile |
$* | The stem with which an implicit rule matches. For example, the target aa.o matches the pattern '%.o', then 'aa' is the stem. |