Will @include be called multiple times for duplicated files?

[Peng Yu]

Suppose that A.awk includes B.awk, C.awk includes B.awk, D.awk
includes A.awk and C.awk, if I include D.awk in another awk file, how
many times B.awk will be accessed by awk? Is it twice or once?

In other words, does awk know B.awk has been included already and
therefore will not try to include it again?

-- 
Regards,
Peng