illegal seek

[smarty]

this code gives an "illegal seek error" on close() call
what is this error and when does it come?

main()
{
int fd,num;
char buf[150];
fd = open ("123.c",O_RDWR );
if(fd!=-1)
{

printf("a file with fd=%d is opened\n",fd);
num=read(fd,buf ,150);
printf("num=%d\ nREAD:%s",num,b uf);
perror("READ");
close(fd);
perror("CLOSE") ;
}
}

[Antoninus Twink]

On 16 May 2008 at 10:25, CBFalconer wrote:

Of course the Twink-troll also snipped my explanation, which
follows below:

Indeed I did. Because it was utter bullshit. It was an expression of
your opinion, which I violently disagree with, and I don't think it is
worthy of a reply. You clearly never get bored of endless rants about
topicality, but I'm no longer rising to the bait.

Watch: I'm snipping it again.

[snip]

which is part of the trolls standard mechanism, aiming to disturb
the normal operation of the newsgroup.

Of course, replying to spam doesn't disturb the normal operation of the
newsgroup in the slightest. Neither does your continual attempts to
drive away new participants in the group by continually spewing out your
tedious views on topicality. And neither does the stream of
embarrassingly wrong answers you provide to questions.

I see no reason to ever use open, close and read, when fopen, fclose
and fread are available everywhere, and portable.

Of course you don't. You have no interest in any program more
complicated than a solution to one of the exercises in K&R. You have an
arrogant disdain for people who dirty their hands with real-world
programming, when they might come across good reasons to use open, close
and read. Here are the first few that spring to mind:

* to be able to work with file permissions and ownership
* getting file information with fstat (e.g. the size of a file)
* locking files with fcntl or flock
* getting file change notifications with fcntl
* to be able to send ioctls to devices

[Walter Roberson]

In article <sl************ *******@nospam. invalid>,
Antoninus Twink <no****@nospam. invalidwrote:

>On 16 May 2008 at 10:25, CBFalconer wrote:

>I see no reason to ever use open, close and read, when fopen, fclose
and fread are available everywhere, and portable.

>Here are the first few that spring to mind:

>* to be able to work with file permissions and ownership
* getting file information with fstat (e.g. the size of a file)
* locking files with fcntl or flock
* getting file change notifications with fcntl
* to be able to send ioctls to devices

Those all involve extensions beyond the perview of C itself, and
are best discussed in a newsgroup that deals with the scope of the
extensions required (e.g., POSIX is going to have different behaviours
than Linux or MS Windows.)

In every extension I can currently think of that supports
the operations listed, open(), close() and read() are unnecessary
for any of the listed operations: those operations work on file
descriptors, and one can determine a FILE's file descriptor using
the fileno() extension upon a file that one has fopen()'d.
And if there are OS's that support file descriptors but do not
offer fileno() but still offer the listed operations, then such
OSs would certainly not be operating in any standardized way, which
would make it even more important to discuss the details in
an appropriate newsgroup rather than here.

--
"This quitting thing, it's a hard habit to break once you start."
-- Walter Matthau

[Keith Thompson]

jacob navia <ja***@nospam.o rgwrites:
[...]

Why would you need to use fileno each time when you just
use open/close etc and be done with it?

You gave no valid reason.

I'm sure there are plenty of valid reasons to use open/close rather
than fileno.

comp.unix.progr ammer would be a great place to discuss those reasons
(if they're not already thoroughly covered in the FAQ).

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"