Re: [MacPerl] sys{open,close,read} and non-sys cousins

[Matthias Ulrich Neeracher <neeri@iis.ee.ethz.ch>]

[The entire topic is not really MacPerl-specific, but I thought I'd clarify the
 situation]
Vicki Brown <vlb@cfcl.com> writes:
>At 09:20 -0500 98/06/11, Mark Manning/Simulacron I wrote:
>> On the usage of OPEN with SYSREAD.  You didn't read/remember my entire
>> message.  I said:
>>
>> 	SYSOPEN
>> 	SYSREAD
>> 	SYSWRITE
>> 	CLOSE
>
>Someone can tell me I'm wrong, but...
>
>As near as I can tell going through the Camel, there is no documented
>reason not to use open() with sysread() or sysopen() with read(),

There isn't.

>or to even assume that the sys* functions are somehow "better" than their
>non-sys-prefixed counterparts,

OK, here's the situation:

 - Every file in Perl is a stdio (buffered) stream in the C sense.
 - Every stdio file ultimately interacts with a nonbuffered POSIX stream
   (file or socket).
 - sysread, syswrite, and sysseek operate on the POSIX stream, read, print,
   seek operate on the buffered stream.
 - sysopen opens a POSIX stream, but immediately wraps a buffered stream
   around it.

This means that:

 - streams created with open() and with sysopen() are interchangeable.
 - You should not mix sys- and nonsys versions of {read, write/print, seek} on
   the same stream.
 - Buffered I/O is faster or slower than nonbuffered I/O, depending on the
   situation.
 - Nonbuffered I/O is often preferrable for sockets, since it's more
   predictable.

>> > (And why the CLOSE statement works with the rest of that stuff I have no
>> > idea.  I would have thought there would have been a SYSCLOSE.)

There is only a single kind of file in perl. CLOSE closes both the stdio
stream and the POSIX stream associated with the Perl file.

Matthias

-----
Matthias Neeracher   <neeri@iis.ee.ethz.ch>   http://www.iis.ee.ethz.ch/~neeri
   "These days, though, you have to be pretty technical before you can 
    even aspire to crudeness." -- William Gibson, _Johnny Mnemonic_

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