Re: Quick close of all the open files.

[vamsi krishna]

> > >
> > I checked as follows I did printf("lowest fd = %d",fileno(tmpfile()));
> > it prints 3
>
> Which proves that file descriptor 3 was closed, so tmpfile() was able to
> open it.  This certainly implies that fd 0, 1, 2 (connected to stdin,
> stdout, and stderr streams of stdio) are still open, contrary to your
> statement that *all* of them are closed.

I know 0,1,2 are open (I opened it) no need to tell it specifically,
HOW DO YOU THINK I CAN PRINT SOME THING WITHOUT OPENING THIS
FILES(stdout,stderr)?


> If file descriptor 3 is closed, but 4 is open, what does tmpfile()
> do? Hint - tmpfile() ends up invoking open(), and the manpage for that says:
>
>        Given a pathname for a file, open() returns a file descriptor, a small,
>        non-negative integer for  use  in  subsequent  system  calls  (read(2),
>        write(2), lseek(2), fcntl(2), etc.).  The file descriptor returned by a
>        successful call will be the lowest-numbered file  descriptor  not  cur-
>        rently open for the process.
>
> So.. explain why you think that "all files were closed"?  We know that 0..2
> were open, and we know nothing about 4..1023.
>
> This doesn't look like a kernel bug, you may want to continue the discussion
> on one of the various "beginning Linux C programming" lists.
>
> On Tue, 06 Jun 2006 23:03:38 BST, =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= said:
> > > (Hint - what does that fp->_chain = stderr *really* do? ;)
> >
> > As it touches the innards of the FILE type, it invokes undefined
> > behavior.  Nothing that follows can be considered a bug.
>
> Invoking undefined behavior is often considered a bug itself.  And it's
> certainly happening in userspace.. so there's a userspace bug. ;)
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