[9fans] APE question

[9fans] APE question

[pac]

Friends,

under APE, the following part of code:

                printf("\nQuit [q], confirm [y], or change [menu] settings: ");               
                /* read one char */
                ch = getchar();
 
does not print out the message before waiting for a character input, unless it is flushed
e.g. by adding 
	printf("\n");
before line 3. Is this an intention? If so, could you tell me a better workaround than this with blank printf()?

Sorry fot ignorance,
--peter.

--
Peter A Cejchan
biologist
Acad. Sci., Prague, CZ
<cej at cejchan dot gli dot cas dot cz>

Re: [9fans] APE question

[Douglas A. Gwyn]

pac wrote:
> If only I were a bit better programmer to figure out that fflush()
> works with stdout, too (sigh, sigh)...

Actually, fflush() is not required to "flush" type-ahead input
on stdin; it has undefioned behavior on input streams.

Re: [9fans] APE question

[pac]

Hi,

thanks to all who answered! I have still much, much to learn!

--peter


--
Peter A Cejchan
biologist
Acad. Sci., Prague, CZ
<cej at cejchan dot gli dot cas dot cz>

Re: [9fans] APE question

[Howard Trickey]

Whoops,
	setvbuf(stdout, _IONBF, BUFSIZ);
should have been
	setvbuf(stdout, 0, _IONBF, BUFSIZ);

Re: [9fans] APE question

[Howard Trickey]

> under APE, the following part of code:

>       printf("\nQuit [q], confirm [y], or change [menu] settings: ");
>        /* read one char */
>        ch = getchar();

According to the C standard, "The standard input and output streams are
fully buffered if and only if the stream can be determined not to refer to
an interactive device."  It doesn't say whether to use line buffering or no
buffering in the interactive case.  I chose line buffering.  So the above
might have worked if you'd put a '\n' at the end of the printf string.  (But
only "might": the code to test whether a file is "interactive" ---
isatty --- is hacky in the extreme, and only works sometimes; with Plan 9's
namespace stuff, it is hard to get right.)

As well as the fflush solution given earlier, you could also put a call like

	setvbuf(stdout, _IONBF, BUFSIZ);

near the beginning of your program.  But the fflush solution is probably
better.

Re: [9fans] APE question

[Laura Creighton]

Heh.  What you need is a month or so watching us try to do 
computational biology.  You would be most amused.

Laura Creighton

Re: [9fans] APE question

[Boyd Roberts]

pac wrote:
> I'll give it a try. If only I were a bit better programmer to
> figure out that fflush() works with stdout, too (sigh, sigh)...

Oh, stdio buffering has never been straightforward or obvious.

Re: [9fans] APE question

[pac]

>> 
>> Put an fflush(stdout) twixt the printf and getchar?
I'll give it a try. If only I were a bit better programmer to figure out that fflush() works with stdout, too (sigh, sigh)...

--cheers, peter

Re: [9fans] APE question

[rog]

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i think on some platforms reading from stdin does an automatic flush on
stdout.  this might even be the standard.

anyway, it's probably safer to do

                printf("\nQuit [q], confirm [y], or change [menu] settings: ");   
                fflush(stdout);            
                /* read one char */
                ch = getchar();


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To: 9fans@cse.psu.edu
Subject: [9fans] APE question
Date: Fri, 12 Oct 2001 16:21:26 +0200
Message-ID: <cej-1011012162124.A01246@cejchan.gli.cas.cz>

Friends,

under APE, the following part of code:

                printf("\nQuit [q], confirm [y], or change [menu] settings: ");               
                /* read one char */
                ch = getchar();
 
does not print out the message before waiting for a character input, unless it is flushed
e.g. by adding 
	printf("\n");
before line 3. Is this an intention? If so, could you tell me a better workaround than this with blank printf()?

Sorry fot ignorance,
--peter.

--
Peter A Cejchan
biologist
Acad. Sci., Prague, CZ
<cej at cejchan dot gli dot cas dot cz>

Re: [9fans] APE question

[presotto]

[-- Attachment #1: Type: text/plain, Size: 53 bytes --]

Put an fflush(stdout) twixt the printf and getchar?

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From: pac <cej@cejchan.gli.cas.cz>
To: 9fans@cse.psu.edu
Subject: [9fans] APE question
Date: Fri, 12 Oct 2001 16:21:26 +0200
Message-ID: <cej-1011012162124.A01246@cejchan.gli.cas.cz>

Friends,

under APE, the following part of code:

                printf("\nQuit [q], confirm [y], or change [menu] settings: ");               
                /* read one char */
                ch = getchar();
 
does not print out the message before waiting for a character input, unless it is flushed
e.g. by adding 
	printf("\n");
before line 3. Is this an intention? If so, could you tell me a better workaround than this with blank printf()?

Sorry fot ignorance,
--peter.

--
Peter A Cejchan
biologist
Acad. Sci., Prague, CZ
<cej at cejchan dot gli dot cas dot cz>