On Mon, Sep 18, 2006 at 11:42:29AM +0200, Roman Zilka wrote:
> > I was wondering why Linux doesn't treat directories like files, as many
> > other unix implementations do.
> > For example, in Linux, you can't do 'cat .' while on FreeBSD you can.
> > Why? There is a practical reason?
>
> I'd say it's not a matter of how Linux treats directories
> (putting aside the problem of diverse filesystems), but how
> coreutils or "cat", to be precise, treats directories. You could just as
> well implement such a feature into 'cat' which would make it behave like
> it does on FreeBSD when called on a directory. As to why Linux's "cat"
> acts the way it does...try asking GNU guys.:)
I was not talking about cat itself, but about open() and read().
> Btw, in my place:
> $ uname -a
> FreeBSD howdy123 6.1-PRERELEASE FreeBSD 6.1-PRERELEASE #0: Wed Apr 5
> 12:22:42 CEST 2006 [EMAIL PROTECTED]:/usr/obj/usr/src/sys/GORGO i386
> $ cat .
> cat: .: Is a directory
> $
Strange, my FreeBSD box, things works differently...
I was asking because, in FreeBSD I can do this bit of magic, but in
Linux not (not really useful, just proving that in Linux, not everything
is a file ;-).
[EMAIL PROTECTED]:~/ $ uname -a
FreeBSD watson.octopus 6.1-STABLE FreeBSD 6.1-STABLE #14: Wed Aug 23 14:47:09
CEST 2006 [EMAIL PROTECTED]:/usr/obj/usr/src/sys/WATSON i386
[EMAIL PROTECTED]:~ $ mkdir prova
[EMAIL PROTECTED]:~ $ od -c prova/
0000000 020 342 002 \0 \f \0 004 001 . \0 \0 \0 001 p 001 \0
0000020 364 001 004 002 . . \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
0000040 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
*
0001000
[EMAIL PROTECTED]:~ $ cd prova/
[EMAIL PROTECTED]:~/prova $ touch file
[EMAIL PROTECTED]:~/prova $ touch file2
[EMAIL PROTECTED]:~/prova $ od -c .
0000000 020 342 002 \0 \f \0 004 001 . \0 \0 \0 001 p 001 \0
0000020 \f \0 004 002 . . \0 \0 026 342 002 \0 020 \0 \b 004
0000040 f i l e \0 ` ' 303 032 342 002 \0 330 001 \b 005
0000060 f i l e 2 \0 ' 303 \0 \0 \0 \0 \0 \0 \0 \0
0000100 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
*
0001000
[EMAIL PROTECTED]:~/prova $ rm file
[EMAIL PROTECTED]:~/prova $ od -c .
0000000 020 342 002 \0 \f \0 004 001 . \0 \0 \0 001 p 001 \0
0000020 034 \0 004 002 . . \0 \0 026 342 002 \0 020 \0 \b 004
0000040 f i l e \0 ` ' 303 032 342 002 \0 330 001 \b 005
0000060 f i l e 2 \0 ' 303 \0 \0 \0 \0 \0 \0 \0 \0
0000100 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
*
0001000
[EMAIL PROTECTED]:~/prova $ ls
file2
And it's not caused by special code in od, it's using simple open()
and read() calls, as proved by this simple C code:
[EMAIL PROTECTED]:~ $ cat mycat.c
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int main(int argc, char **argv)
{
int fd;
char buffer;
fd=open(argv[1], O_RDONLY);
while (read(fd, &buffer, 1) == 1)
printf("%c", buffer);
exit(EXIT_SUCCESS);
}
[EMAIL PROTECTED]:~ $ make mycat
cc -O2 -pipe -march=pentium4 mycat.c -o mycat
[EMAIL PROTECTED]:~ $ ./mycat prova | od -c
0000000 020 342 002 \0 \f \0 004 001 . \0 \0 \0 001 p 001 \0
0000020 034 \0 004 002 . . \0 \0 026 342 002 \0 020 \0 \b 004
0000040 f i l e \0 ` ' 303 032 342 002 \0 330 001 \b 005
0000060 f i l e 2 \0 ' 303 \0 \0 \0 \0 \0 \0 \0 \0
0000100 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 \0
*
0001000
Bye.
--
* Pillon Matteo
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