Pattern-Matching Rules

Pattern-matching rules have been added to simplify the process of adding new implicit rules of your own design. A target entry of the form:

tp%ts : dp%ds
      rule

defines a pattern-matching rule for building a target from a related dependency file. tp is the target prefix; ts, its suffix.dp is the dependency prefix; ds, its suffix. The % symbol is a wild card that matches a contiguous string of zero or more characters appearing in both the target and the dependency file name. For example, the following target entry defines a pattern-matching rule for building a troff output file, with a name ending in .tr from a file that uses the -ms macro package ending in .ms:

%.tr: %ms
troff -t -ms $< > $@

With this entry in the makefile, the command:

make doc.tr

produces:

$ make doc.tr 
troff -t -ms doc.ms > doc.tr

Using that same entry, if there is a file named doc2.ms, the command:

make doc2.tr

produces:

$ make doc2.tr 
troff -t -ms doc2.ms > doc2.tr

An explicit target entry overrides any pattern-matching rule that might apply to a target. Pattern-matching rules, in turn, normally override implicit rules. An exception to this is when the pattern-matching rule has no commands in the rule portion of its target entry. In this case, make continues the search for a rule to build the target, and uses as its dependency the file that matched the (dependency) pattern.