Hi everybody, in a french C book, the author says that only {fgetc,
getc, getchar, fgetwc, getwc, getwchar, fgets, gets, fgetws, getws,
fputc, putc, putchar, fputwc, putwc, putwchar, fputs, puts, fputws}
are guaranteed to set the end-of-file indicator when the end-of-file
is reached, but in C99 standard, I find p 288 (ISO/IEC 9899:TC3
Committee Draft — Septermber 7, 2007 WG14/N1256)
/* =============== ============== */
#include <stdio.h>
/* ... */
int count; float quant; char units[21], item[21];
do {
count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
fscanf(stdin,"% *[^\n]");
} while (!feof(stdin) && !ferror(stdin)) ;
/* =============== ============== */
It seems to say that fscanf family function set end-of-file indicator
too? which functions set the end-of-file indicator?
Aug 4 '08
80  6491 
Eric Sosman wrote:
....
statement about all input functions. (Indeed, the Standard never
defines "input functions" as such, although it does define some
close relatives.)
If we take the commonsense view that "input functions" are the
"wide character input functions" (7.19.1p5) ...
Which starts out saying "The input/output functions are given the
following collective terms"
... plus fgetc, fgets, fread,
fscanf, getc, getchar, gets, scanf, vfscanf, and vscanf,
All of which fall into the category defined by 7.19.1p5 as "byte input/
output functions".
The standard may fail to distinguish between byte input and byte
output functions, but is anyone seriously in doubt as to which of the
byte input/output functions are input functions, and which ones are
output functions?
... I believe
that the description of each says it can set the end-of-file
indicator. (I haven't checked, but you're welcome to -- and
I have. The ones that process more than one character at a time don't
say so directly. You have to invoke 7.19.3p11 to determine that they
are also required to set it. ja*********@ver izon.net wrote:
Eric Sosman wrote:
...
>statement about all input functions. (Indeed, the Standard never
defines "input functions" as such, although it does define some
close relatives.)
If we take the commonsense view that "input functions" are the
"wide character input functions" (7.19.1p5) ...
Which starts out saying "The input/output functions are given the
following collective terms"
>... plus fgetc, fgets, fread,
fscanf, getc, getchar, gets, scanf, vfscanf, and vscanf,
All of which fall into the category defined by 7.19.1p5 as "byte input/
output functions".
The standard may fail to distinguish between byte input and byte
output functions, but is anyone seriously in doubt as to which of the
byte input/output functions are input functions, and which ones are
output functions?
I'd say that's the commonsense view. In fact, I *did* say
that's the commonsense view. Not sure what the argument's about ...
-- Er*********@sun .com
On 4 août, 22:48, Eric Sosman <Eric.Sos...@su n.comwrote:
Eric Sosman wrote:
nicolas.sit...@ gmail.com wrote:
On 4 août, 21:30, Eric Sosman <Eric.Sos...@su n.comwrote:
nicolas.sit... @gmail.com wrote:
OK OK, everybody seems to be ok to say that all I/O functions can
potentially set/clear the end-of-file indicator, but nobody give me
normative reference, and the author says that nothing in the C99 says
that all I/O functions can set/clear end-of-file indicator!!!
>* * *The normative reference is section 7.19 of the Standard.
I looked at this section, but I didn't find anything saying clearly
that all IO input functions set/clear the end-of-file indicator!
* * It's in the same paragraph that says the Moon is made of
green cheese. *In other words, the Standard says no such thing:
You are searching for the normative text of a falsehood.
* * Is it possible that you have confused the end-of-file
indicator with the error indicator? *They are not the same.
* * *Pardon me; I overlooked the insertion of the word "input" in
your restatement of the question. *Yes, the Standard says that all
input functions can set the end-of-file indicator, but it says so
in the descriptions of the individual functions, not as a blanket
statement about all input functions. *(Indeed, the Standard never
defines "input functions" as such, although it does define some
close relatives.)
* * *If we take the commonsense view that "input functions" are the
"wide character input functions" (7.19.1p5) plus fgetc, fgets, fread,
fscanf, getc, getchar, gets, scanf, vfscanf, and vscanf, I believe
that the description of each says it can set the end-of-file
indicator. *(I haven't checked, but you're welcome to -- and
maybe to file a Defect Report if any of them forgets to!) *You can
also search the function descriptions for those that clear or can
clear the end-of-file indicator; it would be somewhat clumsier to
make a blanket statement about the latter category.
--
Eric.Sos...@sun .com
I checked and for example, the fscanf function, nothing says that it
sets the end-of-file indicator except perhaps this example :
#include <stdio.h>
/* ... */
int count; float quant; char units[21], item[21];
do {
count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
fscanf(stdin,"% *[^\n]");
} while (!feof(stdin) && !ferror(stdin)) ;
On Mon, 4 Aug 2008 12:50:23 -0700 (PDT), ni************@ gmail.com
wrote:
>On 4 août, 21:30, Eric Sosman <Eric.Sos...@su n.comwrote:
>nicolas.sit... @gmail.com wrote:
OK OK, everybody seems to be ok to say that all I/O functions can
potentially set/clear the end-of-file indicator, but nobody give me
normative reference, and the author says that nothing in the C99 says
that all I/O functions can set/clear end-of-file indicator!!!
* * *The normative reference is section 7.19 of the Standard.
--
Eric.Sos...@su n.com
I looked at this section, but I didn't find anything saying clearly
that all IO input functions set/clear the end-of-file indicator!
Since it is obviously false, you shouldn't. Read 7.19.3-11 followed
by 7.19.7.1-3 to learn when it is set. You should then be able to
find on your own when it is cleared.
--
Remove del for email
On 4 août, 22:58, jameskuy...@ver izon.net wrote:
Eric Sosman wrote:
I have. The ones that process more than one character at a time don't
say so directly. You have to invoke 7.19.3p11 to determine that they
are also required to set it.
11 The wide character input functions read multibyte characters from
the stream and convert
them to wide characters as if they were read by successive calls to
the fgetwc function.
Each conversion occurs as if by a call to the mbrtowc function,
with the conversion state
described by the stream’s own mbstate_t object. The byte input
functions read
characters from the stream as if by successive calls to the fgetc
function.
Many thanks to everybody, this time it's clear for me.
On Mon, 04 Aug 2008 14:06:55 -0700, nicolas.sitbon wrote:
I checked and for example, the fscanf function, nothing says that it
sets the end-of-file indicator
Okay, maybe an example is clearer for you.
7.19.1p5 (Input/output <stdio.h>; Introduction)
"The byte input/output functions [...]: [...], fscanf, [...]"
7.19.3p11 (Files)
"The byte input functions read characters from the stream as if by
successive calls to the fgetc function."
7.19.7.1p3 (The fgetc function)
"If [...] the stream is at end-of-file, the end-of-file indicator for the
stream is set [...]"
Yes, it doesn't explicitly say that fscanf sets the end-of-file indicator.
But a conforming implementation where fscanf *doesn't* set the end-of-file
indicator cannot exist; it would have to break one of these three
requirements. Either it doesn't classify fscanf as a byte input function,
or it doesn't make byte input functions read input as if by successive
calls to fgetc, or it doesn't make fgetc set the end-of-file indicator.
Malcolm McLean wrote, On 04/08/08 19:27:
>
<ni************ @gmail.comwrote in message news:
>Hi everybody, in a french C book, the author says that only {fgetc,
getc, getchar, fgetwc, getwc, getwchar, fgets, gets, fgetws, getws,
fputc, putc, putchar, fputwc, putwc, putwchar, fputs, puts, fputws}
are guaranteed to set the end-of-file indicator when the end-of-file
is reached.
The book is wrong, at least to all intents and purposes. EOF will be
returned after the contents of the file have been exhausted by any of
the read functions. feof() returns true after the first read to return EOF.
The above is at least misleading. EOF is a macro which evaluates to an
integer constant. Since some of the input functions return pointers you
are obviously wrong about all of the input functions being able to
return its value. Also for those which can return EOF they can do so
because of an error, and if it is an error causing the routine to return
EOF then feof() will not return true but ferror() will.
I think what he is thinking is that if a call to a function like
fscanf() doesn't match the input format than you'll get a partial read -
the function will return the number of arguments successfully converted
- and EOF may not be set, even if you are very close to the end of the
file and have no complete records left.
Well, that appears to not be what the OP's book was referring to, but it
is true.
--
Flash Gordon
In article <50************ *************** *******@f63g200 0hsf.googlegrou ps.com>,
<ni************ @gmail.comwrote :
>OK OK, everybody seems to be ok to say that all I/O functions can
potentially set/clear the end-of-file indicator, but nobody give me
normative reference, and the author says that nothing in the C99 says
that all I/O functions can set/clear end-of-file indicator!!!
All I/O function don't, for instance, I seem to recal ferror() does not,
although you may argue that that call does not do any real I/O even though
it is in the I/O family. Also, some involve WEOF.
However, C99 specifically mentions which routines return EOF et al,
and that's a real lot of them.
--
Greg Comeau / 4.3.10.1 with C++0xisms now in beta!
Comeau C/C++ ONLINE == http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?
In article <1217878106.929 229@news1nwk>,
Eric Sosman <Er*********@su n.comwrote:
>... set ... the end-of-file
indicator. putc(), for example, cannot.
Dunno if we're using different words or not, but
putc certainly can return EOF.
--
Greg Comeau / 4.3.10.1 with C++0xisms now in beta!
Comeau C/C++ ONLINE == http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?
On Aug 5, 3:40 am, com...@panix.co m (Greg Comeau) wrote:
In article <1217878106.929 229@news1nwk>,
Eric Sosman <Eric.Sos...@su n.comwrote:
... set ... the end-of-file
indicator. putc(), for example, cannot.
Dunno if we're using different words or not, but
putc certainly can return EOF.
The end of file indicator has nothing to do with the EOF macro.
When putc returns EOF, it means one of the following
o error with the stream; ferror() should return non-zero.
o EOF is a valid byte value that has been written to the stream.
Mr Sosman is talking about file streams that feof() returns non-zero
for. (ie the eof flag is set).
putc cannot set that flag. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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