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  6419  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.
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!
Hasn't it been made clear to you by now that only one poster has said
that all functions that perform an I/O operation set these flags, and
that he was overstating his case, as has been explained more than once?
On 4 août, 21:59, santosh <santosh....@gm ail.comwrote:
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!
Hasn't it been made clear to you by now that only one poster has said
that all functions that perform an I/O operation set these flags, and
that he was overstating his case, as has been explained more than once?
read what I said : all IO INPUT functions ni************@ gmail.com wrote:
On 4 août, 21:59, santosh <santosh....@gm ail.comwrote:
>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!
Hasn't it been made clear to you by now that only one poster has said
that all functions that perform an I/O operation set these flags, and
that he was overstating his case, as has been explained more than
once?
read what I said : all IO INPUT functions
You have already been told that all input in C is done as if it is
composed of one or more calls to fgetc, and fgetc can most certainly
set the end-of-file indicator, and it's implied that other input
functions modelled on top of it, must also do so. Indeed they have no
choice but to do so. However they do have different methods of
notifying the user of such an exception. For example fgets returns a
null pointer, fread returns a short item count, scanf returns EOF etc.
In all cases you can always determine whether a particular FILE stream
is at end-of-file by calling the feof function, and whether an I/O
error has occurred during the last access by using the ferror function.
santosh wrote:
Eric Sosman wrote:
>ni************@ 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!!!
Unless the post hasn't reached my news server yet, nobody has
claimed that all I/O functions can set or clear the end-of-file
indicator. putc(), for example, cannot. Nor can ftell(), nor
setvbuf(), nor feof(), nor a bunch of others.
To quote vippstar:
All functions that perform IO operations. (ie even perror() can set
the 'error' indicator for stderr if an error occurs at writing)
The O.P. asked about the end-of-file indicator. The end-of-file
indicator and the error indicator are separate indicators, and are
set and cleared under different circumstances.
-- Er*********@sun .com
nicolas.sit...@ gmail.com wrote:
On 4 ao�t, 21:30, Eric Sosman <Eric.Sos...@su n.comwrote:
...
� � �The normative reference is section 7.19 ofthe Standard.
--
Eric.Sos...@sun .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!
It doesn't explain it in those terms. You have to follow several
intermediate steps.
7.19.7.1p3 says that fgetc() sets the end-of-file indicator.
7.24.3.1p3 says the same for fgetwc(). All wide character input
functions have their behavior defined in terms of successive calls to
fgetwc(), and all byte input functions have their behavior defined in
terms of repeated calls to fgetc() (7.19.3p11). All of the input
functions are defined as either wide character input functions or byte
input functions (7.19.1p3) . Those functions don't have to actually
call fgetc()/fgetwc(), but must produce the same behavior as if they
called fgetc()/fgetwc(), which means that they must set the end-of-
file indicator, when appropriate.
On 4 août, 22:14, santosh <santosh....@gm ail.comwrote:
nicolas.sit...@ gmail.com wrote:
On 4 août, 21:59, santosh <santosh....@gm ail.comwrote:
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!
Hasn't it been made clear to you by now that only one poster has said
that all functions that perform an I/O operation set these flags, and
that he was overstating his case, as has been explained more than
once?
read what I said : all IO INPUT functions
You have already been told that all input in C is done as if it is
composed of one or more calls to fgetc, and fgetc can most certainly
set the end-of-file indicator, and it's implied that other input
functions modelled on top of it, must also do so. Indeed they have no
choice but to do so. However they do have different methods of
notifying the user of such an exception. For example fgets returns a
null pointer, fread returns a short item count, scanf returns EOF etc.
In all cases you can always determine whether a particular FILE stream
is at end-of-file by calling the feof function, and whether an I/O
error has occurred during the last access by using the ferror function.
sorry but, one more time, you don't answer me : can you say precisely,
where in the normative reference it is write that all IO INPUT
functions clear/set the end-of-file indicator cause if I write to the
author without any proof...
Eric Sosman wrote:
santosh wrote:
>Eric Sosman wrote:
>>ni************@ gmail.com wrote:
OK OK, everybody seems to be ok to say that all I/O functions can
potentiall y 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!!!
Unless the post hasn't reached my news server yet, nobody has
claimed that all I/O functions can set or clear the end-of-file
indicator. putc(), for example, cannot. Nor can ftell(), nor
setvbuf(), nor feof(), nor a bunch of others.
To quote vippstar:
All functions that perform IO operations. (ie even perror() can set
the 'error' indicator for stderr if an error occurs at writing)
The O.P. asked about the end-of-file indicator. The end-of-file
indicator and the error indicator are separate indicators, and are
set and cleared under different circumstances.
You're right. Apologies to vippstar for misquoting him. 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.
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.
-- Er*********@sun .com
On 4 août, 22:28, Eric Sosman <Eric.Sos...@su n.comwrote:
* * *Is it possible that you have confused the end-of-file
indicator with the error indicator? *They are not the same.
--
Eric.Sos...@sun .com
In fact, the author says that except the functions I mentioned above,
all other are not guaranteed to set the end-of-file OR error
indicator, and he says that other functions are not portable if used
in this way. For french programmers who want to verify my saying, the
book is "méthodolog ie de la programmation en C, norme C99, API POSIX"
de Achille Braquelaire.
Eric Sosman wrote:
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
potentiall y 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.
-- Er*********@sun .com This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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