On Mon, 2011-04-25 at 22:17 +0800, loody wrote:
> 1. There is a section, 10.5.3 Automatic Variables, which explain the
> meaning and usage of automatic variables.
> But I cannot find the usage of $< in the manual.
> Would anyone tell me where it is?
It's right there, in that section:
`$<'
The name of the first prerequisite. If the target got its
commands from an implicit rule, this will be the first
prerequisite added by the implicit rule (*note Implicit Rules::).
Does your info reader support a search function?
> 2. in that section, there is an example say "if "$@" is "dir/foo.o",
> $(@D) will be "dir""
> does that mean if our makefile as below:
>
> dir/foo.o dir/abc.o dir/def.o : header.h
> commands
>
> and $@ in the commands will be dir/foo.o and $(D@) will be dir?
Yes, when make is building dir/foo.o. When make is building dir/abc.o
then $@ will be dir/abc.o.
Remember that the rule above is interpreted by make to be the same as:
dir/foo.o : header.h
commands
dir/abc.o : header.h
commands
dir/def.o : header.h
commands
Make does not think that one invocation of the "commands" recipe will
build all three targets.
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