Makefile中的 Automatic Variables 含义

$@    The filename representing the target.

$%    The filename element of an archive member specification.

$<    The filename of the first prerequisite.

$?    The names of all prerequisites that are newer than the target, separated by spaces.

$^    The filenames of all the prerequisites, separated by spaces. This list has duplicate filenames removed since for most uses, such as compiling, copying, etc., duplicates are not wanted.

$+    Similar to $^, this is the names of all the prerequisites separated by spaces, except that $+ includes duplicates. This variable was created for specific situations such as arguments to linkers where duplicate values have meaning.

$*    The stem of the target filename. A stem is typically a filename without its suffix. (We’ll discuss how stems are computed later in the section “Pattern Rules.”) Its use outside of pattern rules is discouraged.