make: Wildcard Examples
1
1 4.4.1 Wildcard Examples
1 -----------------------
1
1 Wildcards can be used in the recipe of a rule, where they are expanded
1 by the shell. For example, here is a rule to delete all the object
1 files:
1
1 clean:
1 rm -f *.o
1
1 Wildcards are also useful in the prerequisites of a rule. With the
1 following rule in the makefile, 'make print' will print all the '.c'
1 files that have changed since the last time you printed them:
1
1 print: *.c
1 lpr -p $?
1 touch print
1
11 This rule uses 'print' as an empty target file; see ⇒Empty Target
Files to Record Events Empty Targets. (The automatic variable '$?' is
11 used to print only those files that have changed; see ⇒Automatic
Variables.)
1
1 Wildcard expansion does not happen when you define a variable. Thus,
1 if you write this:
1
1 objects = *.o
1
1 then the value of the variable 'objects' is the actual string '*.o'.
1 However, if you use the value of 'objects' in a target or prerequisite,
1 wildcard expansion will take place there. If you use the value of
1 'objects' in a recipe, the shell may perform wildcard expansion when the
1 recipe runs. To set 'objects' to the expansion, instead use:
1
1 objects := $(wildcard *.o)
1
1 ⇒Wildcard Function.
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