NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/5433

Internet Message Format | 1996-08-05 | 2.6 KB

Path: mail2news.demon.co.uk!genesis.demon.co.uk
From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: Unbuffered character input...
Date: Mon, 12 Feb 96 16:02:26 GMT
Organization: none
Message-ID: <[e-mail]>
References: <[e-mail]> <[e-mail]> <4f7hlf$[e-mail]> <[e-mail]> <4f8kat$[e-mail]> <[e-mail]> <danpop.823811815@rscernix>
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In article <danpop.823811815@rscernix> [e-mail] "Dan Pop" writes:

>In <[e-mail]> Lawrence Kirby <[e-mail]>
> writes:
>
>>In article <4f8kat$[e-mail]>
>>           [e-mail] "Peter Seebach" writes:
>>
>>>In article <[e-mail]>,
>>>Dan Pop  <[e-mail]> wrote:
>>>>But even on systems where it is not, it still saves processor time.
>>>>The cpu overhead of making a single OS call to get a complete line of input
>>>>is smaller (sometimes significantly smaller) than the overhead of making
>>>>N OS calls, one for each character of the line.  The stdio library tries
>>>>to do its best to minimize the number of (expensive) OS calls.
>>
>>The stdio library typically reads characters as soon as they are available
>>so it does very little in this respect except provide suitable buffering
>>when more than one character happens to be available on a read. This is
>>clearly significant for file I/O but whether terminal I/O makes user typed
>>characters immediately available or not is usually purely a function of the
>>OS. Setting line buffering on input streams on many/most stdio libraries
>>doesn't do anything special.
>
>Because the line buffering is performed by the tty driver.  The tty driver
>won't (unless explicitly asked) make characters available as soon as they
>are typed and the stdio library doesn't attempt to get them as soon as
>they're typed.  It looks like line buffered terminal input to me, unless
>I'm missing something.

(Much quoting but this is all rather context-sensitive)

Agreed. My point was simply to stress that in this case this is not a
function of stdio, rather it is a function of the tty driver.

--
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Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
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