Makefile 规则

1 Automatic Variables

$@ The filename representing the target.

$% The filename element of an archive member specification.

$< The filename of the first prerequi$? 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 dupli-

   cate 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 situa-

   tions 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.

2 VPATH

You can tell make to look in different directories for its source files using the VPATH

and vpath features. To fix our immediate problem, we can add a VPATH assignment to

the makefile:

VPATH = src

3 vpath

The vpath directive is a more precise way to achieve our goals. The syntax of this

directive is:

So our previous VPATH use can be rewritten as:

    vpath %.c src

    vpath %.h include