[Fwd: Re: printf without '\n']

[Fwd: Re: printf without '\n']

[Gerardo García Peña]

[-- Attachment #1: Type: text/plain, Size: 1 bytes --]



[-- Attachment #2: Re: printf without '\n' --]
[-- Type: message/rfc822, Size: 1752 bytes --]

From: "Gerardo García Peña" <gerardo@kung-foo.dhs.org>
To: Ricardo Catalinas Jimenez <th1nk3r@server01.org>
Subject: Re: printf without '\n'
Date: Tue, 25 Oct 2005 17:45:19 +0200
Message-ID: <435E530F.5020004@kung-foo.dhs.org>

Ricardo Catalinas Jimenez wrote:

>Newbie simple question:
>
>With a code like this:
>
>.section .data
>MSG:
>	.ascii "Hello\0"
>.section .text
>	.globl _start
>_start:
>	pushl %ebp
>	movl %esp, %ebp
>
>	pushl $MSG
>	call printf
>
>        movl %ebp, %esp
>        popl %ebp
>
>	movl $1, %eax
>	xorl %ebx, %ebx
>	int $0x80
>
>I compiled it with:
>as code.s -o code.o; ld --dynamic-linker /lib/ld-linux.so.2 -lc \
>	test.o -o test
>
>With that ascii string, nothing is printed but when I use "Hello\n\0" it
>works fine. 
>
>What is the reason for not printing the string if there isn't a '\n' in
>it?
>
>I something related with the buffered (by lines) IO?
>
>Why with a C program it does not happend.
>
>Thanks in advance.
>
>  
>
You should flush stdio(3) buffers before exiting. Try with fflush(3).
This program exits with the _exit(2) system call without flushing 
buffers nor deinitializing C standard libraries.
If you try to exit with exit(3) libc it will work.

You can the behaviour of your current program with this simple C program:

  main()
  {
    printf("hello");
    _exit(0);
  }

If you change _exit(2) by exit(3) it will work...

Luck,
Gerardo García Peña