Date: Wed, 30 Jan 2002 22:56:21 -0800 From: "Jeff Shevlen" <jeff@dsl.ca> To: "Giorgos Keramidas" <keramida@freebsd.org> Cc: <freebsd-questions@FreeBSD.ORG> Subject: Re: CVSup release info Message-ID: <047201c1aa24$6423d8e0$b300a8c0@wenk> References: <20020131031616.GA73680@hades.hell.gr>
next in thread | previous in thread | raw e-mail | index | archive | help
That's interesting. I had no idea shell scripts could interface with
C like so. I have one last question in regards to the script. I
looked at man cpp and I didn't see anything about "-E"; not to
mention the " -" after the E. What does all this do? I ran the
script without any modifiers to cpp and I got the same result as with
"-E -" !
: > : $ ( echo '#include <sys/param.h>' ; echo __FreeBSD_version ) |
cpp -E - | tail -1
: > : 500028
:
: Ah but it is simple really. cpp(1) is a preprocessor. It doesn't
: care if input comes from standard input. The symbol
_FreeBSD_version
: is defined in /usr/src/sys/sys/param.h (which finally is copied by
: installworld to /usr/include/sys/param.h). The two 'echo' commands
: produce a minimal C 'testbed' like below:
:
: $ ( echo '#include <sys/param.h>' ; echo __FreeBSD_version )
: #include <sys/param.h>
: __FreeBSD_version
:
: This piped into cpp, will be preprocessed, and __FreeBSD_version
(the
: last line of the source) be substituted with it's value as defined
in
: /usr/include/sys/param.h. The final tail is fairly obvious now...
:
: --
: Giorgos Keramidas . . . . . . . . .
keramida@{ceid.upatras.gr,freebsd.org}
: FreeBSD Documentation Project . . . http://www.freebsd.org/docproj/
: FreeBSD: The power to serve . . . . http://www.freebsd.org/
:
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?047201c1aa24$6423d8e0$b300a8c0>