scanf behaviour

[CBFalconer]

Thanks for reply. I give it I try. If this method is working only
on flavours of unix , it's fine with me.

Don't top-post. See the links below.

--
Some informative links:
< <http://www.geocities.com/nnqweb/>
<http://www.catb.org/~esr/faqs/smart-questions.html>
<http://www.caliburn.nl/topposting.html>
<http://www.netmeister.org/news/learn2quote.html>
<http://cfaj.freeshell.org/google/>

 

[Richard Heathfield]

(e-mail address removed) said:

Richard , with all respect

U haven't provided any reference for your claim that fflush( stdin ) is
undefined, so for me
they are still only your words and not "The Standard"

You mean I haven't quoted this often enough before in comp.lang.c? Okay,
here we go again:

4.9.5.2 The fflush function

Synopsis

#include <stdio.h>
int fflush(FILE *stream);

Description

If stream points to an output stream or an update stream in which
the most recent operation was output, the fflush function causes any
unwritten data for that stream to be delivered to the host environment
to be written to the file; otherwise, the behavior is undefined.

If stream is a null pointer, the fflush function performs this
flushing action on all streams for which the behavior is defined
above.


(C99 contains similar wording.)

Read this, for example :

<man page snipped>

Man pages don't define the language.

 

[stasgold]

Thanks for the reference

By the way, the usage of "fflush( stdin ) is quite common :
http://www.google.com/codesearch?hl=en&lr=&q=fflush+stdin

Although it doesn't prove that thousands of lemmings are right

 

[Richard Heathfield]

(e-mail address removed) said:

Thanks for the reference

By the way, the usage of "fflush( stdin ) is quite common :

So is drinking too much. That doesn't make it a wise thing to do.

 

[Default User]

Richard , with all respect

Please don't top-post. Your replies belong following or interspersed
with properly trimmed quotes. See the majority of other posts in the
newsgroup, or:
<http://www.caliburn.nl/topposting.html>

 

[Mark McIntyre]

Well you flush beer pumps to clear out the stale beer.

Beer pumps output beer, they don't suck it back in from your glass....

And while you /can/ flush your stomach after inputting beer, its
considered a impolite.
--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

 

[Mark McIntyre]

I've tested "fflush( stdin );" on both WinXP and SunOS boxes it works
without a glitch.

That means nothing. It may work only in debug mode, or only provided
there is no other file operation going on in another application, or
only on saturdays. Tomorrow, when you're doing a demonstration to your
boss, it may fail.

--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

 

[Mark McIntyre]

Thanks for the reference

By the way, the usage of "fflush( stdin ) is quite common :

so is stepping on landmines, in some countries. Does that make it a
good idea?

http://www.google.com/codesearch?hl=en&lr=&q=fflush+stdin

Google also has 1.5 million articles matching a search for "sh*t
soup".
Remember that a random plunge into the web does not equate to a fact!
--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

 

[Ian Collins]

Beer pumps output beer, they don't suck it back in from your glass....

But they suck it from the barrel and flushing clears the pipes that feed
the pump, which makes them the pump's stdin

And while you /can/ flush your stomach after inputting beer, its
considered a impolite.

I'm sure the Romans would have disagreed, but they didn't have C compilers.

 

[Ian Collins]

Thanks for the reference

By the way, the usage of "fflush( stdin ) is quite common

Probably only on systems where the behaviour is defined and predates
standard C.

 

[Ian Collins]

That means nothing. It may work only in debug mode, or only provided
there is no other file operation going on in another application, or
only on saturdays. Tomorrow, when you're doing a demonstration to your
boss, it may fail.

I don't know about XP, but on Solaris fflush() on an input stream is
defined:

"Flushing an input stream discards any buffered input and
adjusts the file pointer such that the next input operation
accesses the byte after the last one read."

This non-standard behaviour probably goes back to pre-standard days and
should be avoided in portable code.

 

[Mark McIntyre]

But they suck it from the barrel and flushing clears the pipes that feed
the pump, which makes them the pump's stdin

It may surprise you to learn this, given the quality of most beer, but
you do *not* flush the pipecleaner out into the barrel.....

--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

 

[Ian Collins]

It may surprise you to learn this, given the quality of most beer, but
you do *not* flush the pipecleaner out into the barrel.....

I'm not talking about cleaning the pipes, but pulling though to flush
stale beer before serving the first pint of the session, the stretched
analogy being discarding the stale characters from a stream.

 

[Richard Heathfield]

Ian Collins said:

I'm not talking about cleaning the pipes, but pulling though to flush
stale beer before serving the first pint of the session, the stretched
analogy being discarding the stale characters from a stream.

If you insist on pushing this analogy, it's actually equivalent to something
that you might find in start-up code, such as:

memset(_iobuf._bufdata, 0, sizeof _iobuf._bufdata);
_iobuf[_STDOUT]._bufpos=0;

i.e. making sure that no stale characters remain in the output buffer, where
they might get served to a file by mistake.

But in any case it's a lousy analogy.

 

[Richard Heathfield]

Ian Collins said:

Probably only on systems where the behaviour is defined and predates
standard C.

Do you know of any such systems? Note that C was standardised in 1989.

 

[Richard Heathfield]

Ian Collins said:

I don't know about XP, but on Solaris fflush() on an input stream is
defined:

But in C, it isn't, and we discuss C here, not Solaris.

This non-standard behaviour probably goes back to pre-standard days

Unlikely. Do you have evidence to support that suggestion?

and should be avoided in portable code.

Agreed.

 

[Ian Collins]

Ian Collins said:



Unlikely. Do you have evidence to support that suggestion?

I might have, but it would be off topic.

 

[Ian Collins]

Ian Collins said:


Do you know of any such systems? Note that C was standardised in 1989.

SunOS

 

[Richard Heathfield]

Ian Collins said:

SunOS

I can't find any evidence to support your assertion. Can you?

 

[Ian Collins]

Ian Collins said:



I can't find any evidence to support your assertion. Can you?

It wasn't an assertion, just speculation as to why an unmentionable
operating system defined fflush() on an input stream.

SunOS 4 predates ANSI C and it supported the fflush() function. I've
lost my old man pages, so I can't prove the documented behaviour.