A pattern rule contains the character ‘
%’ (exactly one of them)
in the target; otherwise, it looks exactly like an ordinary rule. The
target is a pattern for matching file names; the ‘
%’ matches any
nonempty substring, while other characters match only themselves.
For example, ‘
%.c’ as a pattern matches any file name that ends in
s.%.c’ as a pattern matches any file name that starts
s.’, ends in ‘
.c’ and is at least five characters long.
(There must be at least one character to match the ‘
%’.) The substring
that the ‘
%’ matches is called the stem.
%’ in a prerequisite of a pattern rule stands for the same stem
that was matched by the ‘
%’ in the target. In order for the
pattern rule to apply, its target pattern must match the file name
under consideration and all of its prerequisites (after pattern
substitution) must name files that exist or can be made. These files
become prerequisites of the target.
Thus, a rule of the form
%.o : %.c ; recipe…
specifies how to make a file
n.o, with another file
n.c as its prerequisite, provided that
exists or can be made.
There may also be prerequisites that do not use ‘
%’; such a prerequisite
attaches to every file made by this pattern rule. These unvarying
prerequisites are useful occasionally.
A pattern rule need not have any prerequisites that contain ‘
in fact any prerequisites at all. Such a rule is effectively a general
wildcard. It provides a way to make any file that matches the target
pattern. See Last Resort.
More than one pattern rule may match a target. In this case
make will choose the “best fit” rule. See How Patterns Match.
Pattern rules may have more than one target; however, every target
must contain a
% character. Pattern rules are always treated
as grouped targets (see Multiple Targets in a
Rule) regardless of whether they use the