What are automatic variables (dollar variables) in a
Suppose in your
Makefile you wrote:
prog: main.c clang -o prog main.c
There are a couple of repetitions: you mention
main.c twice, and
prog twice. You can eliminate the repetition with automatic variables:
prog: main.c clang -o $@ $^
$@ (“dollar at”) is part of the
Makefile language. In your recipe, it refers to the thing it is going to build (above, that’s
prog). Mnemonic: it’s the target you’re aiming at.
$^ (“dollar caret”) refers to the dependencies/inputs (above, that’s
main.c). If it contains multiple dependencies, they are separated by spaces.