Re: Re: fgets() fails to read after fread()

["amol pise" <amol_pise%rediffmail.com@localhost>]

Dear Jean-Yves, 
Thanks for the quick response.
I am using NetBsd-3.1 library on my linux system (SysV). The 
lib/libc/stdio/fgets.c code snippet is as below:

$ cat lib/libc/stdio/fgets.c
{{{
 1 /*      $NetBSD: fgets.c,v 1.20 2003/12/14 23:56:28 lukem Exp $ */
}}}

If I do the following fix in NetBsd library it works for me.
(i.e. Commenting the sticky EOF check)

$ cat lib/libc/stdio/refill.c
{{{
 1 /*      $NetBSD: refill.c,v 1.13 2003/08/07 16:43:30 agc Exp $  */
 :
+ #if 0
 86         /* SysV does not make this test; take it out for compatibility */
 87         if (fp->_flags & __SEOF)
 88                 return (EOF);
+ #endif
}}}

Doing the above modification is enough to work for SysV system ?
Please give me inputs on it.

Thank You,
Amol Pise

On Tue, 31 Aug 2010 14:07:05 +0530  wrote
>

On 30 Aug 2010 15:50:44 -0000, "amol pise" 

wrote:

> Here, at line 89, it checks for __SEOF (i.e. sticky EOF) flag, and if it

> set then it returns EOF at line 90. (In my scenario this flag was set by

> fread() at (A)). Hence it returns EOF.

> 

> Then I decided to comment out this EOF check in refill.c (line:89) and

> observed fgets() is able to read "Hello" without any issue. 

> 

> Can you give me some more inputs why this EOF sticky bit check present

in

> NetBsd ? Is it required ?

> 

> I really appreciate the inputs on it.



I suppose it is some kind of divergence between SysV and BSD paradigms.

Normally, you are not supposed to read data after an EOF, though you can

have situations were it may be possible (like terminals, when you exit a

shell with ^D, and your pipe, when trying to get data through fgets after

fread).



One possible fix would be to use another library, or use clearerr() before

fgets.



Anyway, I can't find the code you are mentioning in my current

lib/libc/stdio/fgets.c -- are you sure this one comes from NetBSD?



-- 

Jean-Yves Migeon

jean-yves.migeon%free.fr@localhost