Roland Ver. 4.5 Informações Técnicas descarregar pdf (Página 33)

Chapter 4: Writing Rules 23

$(OBJS): | $(OBJDIR)

$(OBJDIR):

mkdir $(OBJDIR)

Now the rule to create the objdir directory will be run, if needed, before any ‘.o’ is

built, but no ‘.o’ will be built because the objdir directory timestamp changed.

4.3 Using Wildcard Characters in File Names

A single ﬁle name can specify many ﬁles using wildcard characters. The wildcard characters

in make are ‘*’, ‘?’ and ‘[...]’, the same as in the Bourne shell. For example, *.c speciﬁes

a list of all the ﬁles (in the working directory) whose names end in ‘.c’.

The character ‘~’ at the beginning of a ﬁle name also has special signiﬁcance. If alone,

or followed by a slash, it represents your home directory. For example ~/bin expands to

/home/you/bin. If the ‘~’ is followed by a word, the string represents the home directory

of the user named by that word. For example ~john/bin expands to /home/john/bin. On

systems which don’t have a home directory for each user (such as MS-DOS or MS-Windows),

this functionality can be simulated by setting the environment variable HOME.

Wildcard expansion is performed by make automatically in targets and in prerequisites.

In recipes, the shell is responsible for wildcard expansion. In other contexts, wildcard

expansion happens only if you request it explicitly with the wildcard function.

The special signiﬁcance of a wildcard character can be turned oﬀ by preceding it with

a backslash. Thus, foo\*bar would refer to a speciﬁc ﬁle whose name consists of ‘foo’, an

asterisk, and ‘bar’.

4.3.1 Wildcard Examples

Wildcards can be used in the recipe of a rule, where they are expanded by the shell. For

example, here is a rule to delete all the object ﬁles:

clean:

rm -f *.o

Wildcards are also useful in the prerequisites of a rule. With the following rule in the

makeﬁle, ‘make print’ will print all the ‘.c’ ﬁles that have changed since the last time you

printed them:

print: *.c

lpr -p $?

touch print

This rule uses print as an empty target ﬁle; see Section 4.7 [Empty Target Files to Record

Events], page 31. (The automatic variable ‘$?’ is used to print only those ﬁles that have

changed; see Section 10.5.3 [Automatic Variables], page 120.)

Wildcard expansion does not happen when you deﬁne a variable. Thus, if you write this:

objects = *.o

then the value of the variable objects is the actual string ‘*.o’. However, if you use the

value of objects in a target or prerequisite, wildcard expansion will take place there. If

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