10.5.2 Pattern Rule Examples
Here are some examples of pattern rules actually predefined in
make. First, the rule that compiles `.c' files into `.o'
defines a rule that can make any file `x.o' from
`x.c'. The command uses the automatic variables `[email protected]' and
`$<' to substitute the names of the target file and the source file
in each case where the rule applies (see section Automatic Variables).
Here is a second built-in rule:
% :: RCS/%,v
$(CO) $(COFLAGS) $<
defines a rule that can make any file `x' whatsoever from a
corresponding file `x,v' in the subdirectory `RCS'. Since
the target is `%', this rule will apply to any file whatever, provided
the appropriate prerequisite file exists. The double colon makes the rule
terminal, which means that its prerequisite may not be an intermediate
file (see section Match-Anything Pattern Rules).
This pattern rule has two targets:
%.tab.c %.tab.h: %.y
bison -d $<
make that the command `bison -d x.y' will
make both `x.tab.c' and `x.tab.h'. If the file
`foo' depends on the files `parse.tab.o' and `scan.o'
and the file `scan.o' depends on the file `parse.tab.h',
when `parse.y' is changed, the command `bison -d parse.y'
will be executed only once, and the prerequisites of both
`parse.tab.o' and `scan.o' will be satisfied. (Presumably
the file `parse.tab.o' will be recompiled from `parse.tab.c'
and the file `scan.o' from `scan.c', while `foo' is
linked from `parse.tab.o', `scan.o', and its other
prerequisites, and it will execute happily ever after.)