How to find an end of file

[junky_fellow]

What is the proper way of finding an end of file condition while reading
a file ?

How does feof() detects that end of file is reached ?
Does this require support from OS ?

Thanx in advance for any help ...

[Charlie Gordon]

"junky_fell ow" <ju**********@y ahoo.co.in> wrote in message
news:8c******** *************** **@posting.goog le.com...

What is the proper way of finding an end of file condition while reading
a file ?

How does feof() detects that end of file is reached ?
feof() does not detect that end of file is reached, it reports that end of file
was reached during a previous read operation.
Does this require support from OS ?

if files are implemented with the OS, feof() will rely on the OS reporting such
a condition for read operations.
if files are implemented within the C library, the OS is not an issue.

It is important to notice that feof() is counterintuitiv e:
- Whether a read operation that reaches the end of a file set the condition is
not specified : fgets() reading the last line will probably not set it, while
fscanf() eating trailing white space might.
- If the file is being written by another function (or process where that makes
sense), feof() may return non 0 even after more data becomes available for
reading (clearerr() or fseek() may be needed before reading).

As a rule of thumb, only use feof() to disambiguate end of file from read error
after a read operation fails.
Idioms such as while (!feof(f)) { ... } and do { ... } while (!feof(f)); are
bogus and must be avoided.

--
Chqrlie.

PS: I know about 7.19.6.2 example 3 verse 19. This code snipplet is bogus and
useless. AAMOF most do/while loops are bogus anyway.

[Johnathan Doe]

junky_fellow wrote:

What is the proper way of finding an end of file condition while reading
a file ?

How does feof() detects that end of file is reached ?
Does this require support from OS ?
You can do it yourself without feof(), by doing

struct stat statstruct;

stat("filename" , &statstruct) ;

statstruct.st_s ize is the number of bytes in the file.
Thanx in advance for any help ...

Using feof() is easier though.

FILE *fp = fopen(...);

while (!feof(fp)) {
... read stuff
}

[Johnathan Doe]

> Using feof() is easier though.

FILE *fp = fopen(...);

while (!feof(fp)) {
... read stuff
}

And of course as the previous poster said, you may have a short count or
even an error, so take that into account.

while (!feof(fp)) {

/* Short count ? */
n = fread(buffer, ..., fp);

if (n != whatever) {
if (ferror())
... some kind of error
if (feof())
... end of file
}
}

[Joona I Palaste]

Johnathan Doe <No-spam-here-johnathan_doe@! !!nospamthanks! !!fastmail.com. au> scribbled the following:

junky_fellow wrote:

What is the proper way of finding an end of file condition while reading
a file ?

How does feof() detects that end of file is reached ?
Does this require support from OS ?

You can do it yourself without feof(), by doing struct stat statstruct; stat("filename" , &statstruct) ; statstruct.st_s ize is the number of bytes in the file.

No you can't. There is no struct stat or stat() in the C language.

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-------------------------------------------------------- rules! --------/
"You have moved your mouse, for these changes to take effect you must shut down
and restart your computer. Do you want to restart your computer now?"
- Karri Kalpio

[Charlie Gordon]

"Johnathan Doe" <No-spam-here-johnathan_doe@! !!NOSPAMTHANKS! !!fastmail.com. au>
wrote in message
news:41******** *************** @per-qv1-newsreader-01.iinet.net.au ...

Using feof() is easier though.

FILE *fp = fopen(...);

while (!feof(fp)) {
... read stuff
}
And of course as the previous poster said, you may have a short count or
even an error, so take that into account.

The previous poster said to avoid this stupid bogus idiom !
while (!feof(fp)) {

/* Short count ? */
n = fread(buffer, ..., fp);

if (n != whatever) {
if (ferror())
... some kind of error
if (feof())
... end of file
}
}

Instead do this :

for (;;) {
n = fread(buffer, sizeof(type), count, fp);
if (n != count) {
... handle partial read.
if (ferror(f)) {
... handle error and break or return
break;
}
if (feof(f)) {
.. handle end of file and break or return
break;
}
} else {
... handle normal read
}
}

--
Chqrlie.

[Johnathan Doe]

Joona I Palaste wrote:

No you can't. There is no struct stat or stat() in the C language.

Assuming you're working on 99% of OSes out there, yes you can.

[Joona I Palaste]

Johnathan Doe <No-spam-here-johnathan_doe@! !!nospamthanks! !!fastmail.com. au> scribbled the following:

Joona I Palaste wrote:

No you can't. There is no struct stat or stat() in the C language.

Assuming you're working on 99% of OSes out there, yes you can.

Here we discuss 100% of the OSes out there.

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-------------------------------------------------------- rules! --------/
"A computer program does what you tell it to do, not what you want it to do."
- Anon

[CBFalconer]

Johnathan Doe wrote:

Joona I Palaste wrote:

No you can't. There is no struct stat or stat() in the C language.

Assuming you're working on 99% of OSes out there, yes you can.

Read the welcome message. This group deals with the language as
defined by the ISO standards, not some imaginary uncontrolled
offshoot. Reference to non-standard features is off-topic. Also
use of feof for any purpose other than to disambiguae a read error
is almost always an error. You would know all this is you had
bothered to read this group for a period before breaking in with
misinformation.

--
Chuck F (cb********@yah oo.com) (cb********@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

[MarcSmith]

cuz he is using a file pointer can he seek using fseek to the end of th
file, and use ftell to tell him the filesize.

for example:
i assume cuz he is using fgets, feof...ftell and fseek are defined. o
they should be defined.
Code
-------------------
long filesize( FILE *fp )
{
if (fp==NULL) return 0L;
fseek( fp, 0, SEEK_END );
return ftell(fp);
}

-------------------
-
MarcSmit
-----------------------------------------------------------------------
Posted via http://www.codecomments.co
-----------------------------------------------------------------------