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From: diamond@jit533.swstokyo.dec.com (Norman Diamond)
Newsgroups: comp.std.c
Subject: Re: POSIX conversions
Keywords: POSIX
Message-ID: <1991Jun11.005312.591@tkou02.enet.dec.com>
Date: 11 Jun 91 00:53:12 GMT
References: <298@mem.pe-nelson.com>
Sender: usenet@tkou02.enet.dec.com (USENET News System)
Reply-To: diamond@jit533.enet@tkou02.enet.dec.com (Norman Diamond)
Organization: Digital Equipment Corporation Japan , Tokyo
Lines: 32

In article <298@mem.pe-nelson.com> milt@mem.pe-nelson.com (Milt Ratcliff) writes:
>I am trying to make several programs POSIX compliant.  As part of the effort I
>am confronted with a need to convert routines which measure time.
>My question concerns a replacement for the gettimeofday function which will
>provide [high] level of timing resolution within a POSIX routine.  The POSIX
>documents I am reading imply the use of either clock() or times().  My
>intention is to use times() which is required by POSIX while clock() is
>required by Standard C but not POSIX.

The clock() function returns CPU usage, not time of day.
If you want your program to be strictly conformant to ANSI C (i.e. usable
on (approximately) all ANSI-conformant processors), then you want the
time() function.  But you hint that this may not have sufficient resolution
for your application.

So you only want to run on POSIX-conformant processors, and you can call a
POSIX function which meets your needs; that might be times().

>Also, I am not sure of the meaning of 'Standard C'

In this newsgroup, it seems to mean the ANSI 1989 standard, and the
corresponding ISO standard.  Also, a processor-supplied definition of
the macro __STDC__ with value 1 is supposed to mean this standard (though
some non-ANSI vendors have caused problems with this).

>can I expect the results to be equivalent to [...] gettimeofday?

The POSIX newsgroups might be more helpful for you.
--
Norman Diamond       diamond@tkov50.enet.dec.com
If this were the company's opinion, I wouldn't be allowed to post it.
Permission is granted to feel this signature, but not to look at it.