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Re: About "$(if $(KBUILD_VERBOSE:1=),@)"

From: Paul D. Smith
Subject: Re: About "$(if $(KBUILD_VERBOSE:1=),@)"
Date: Fri, 26 May 2006 15:12:59 -0400

%% "zong jians" <address@hidden> writes:

  zj> In the linux kernel makefile,there is some words like
  zj> "$(if $(KBUILD_VERBOSE:1=),@)" in some line.

The syntax $(VAR:x=y) is syntactic sugar (shorthand) for:

    $(patsubst x,y,$(VAR))

In the special case where either "x" or "y" don't contain a pattern
character (%), it's considered to be prepended; so it would be
equivalent to:

    $(patsubst %x,%y,$(VAR))

or in the above example:

    $(if $(patsubst %1,%,$(KBUILD_VERBOSE)),@)

which essentially evaluates to "@" if the value of KBUILD_VERBOSE is any
value other than "1", and empty if it's exactly "1".

See the GNU make manual for details.

 Paul D. Smith <address@hidden>          Find some GNU make tips at:            
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist

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