/dev/zero

/dev/zero

[blesson paul]

Hi all
               I am newbie to linux kernel. What is the use of /dev/zero. 
Why it is created and how to use it
regards
Blesson Paul



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Re: /dev/zero

[Frank Schaefer]

On Fri, 2002-04-12 at 08:46, blesson paul wrote:
> Hi all
>                I am newbie to linux kernel. What is the use of /dev/zero. 
> Why it is created and how to use it
> regards
> Blesson Paul
> 
> 
> 
> _________________________________________________________________
> Chat with friends online, try MSN Messenger: http://messenger.msn.com
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> Please read the FAQ at  http://www.tux.org/lkml/
> 
Hi,

/dev/zero is a data source. It delivers zeroes ( maybe that's why this
name ;-).

BTW: You are new to the linux kernel or new to linux / unix?

Regards
Frank

RE: /dev/zero

[Rowan Ingvar Wilson]

Just as a matter of interest myself...what is it's actual function? It
is used during kernel debugging to supply an input?

-----Original Message-----
From: linux-kernel-owner@vger.kernel.org
[mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Frank Schaefer
Sent: 12 April 2002 08:19
To: linux-kernel@vger.kernel.org
Subject: Re: /dev/zero

On Fri, 2002-04-12 at 08:46, blesson paul wrote:
> Hi all
>                I am newbie to linux kernel. What is the use of
/dev/zero. 
> Why it is created and how to use it
> regards
> Blesson Paul
> 
> 
> 
> _________________________________________________________________
> Chat with friends online, try MSN Messenger: http://messenger.msn.com
> 
> -
> To unsubscribe from this list: send the line "unsubscribe
linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 
Hi,

/dev/zero is a data source. It delivers zeroes ( maybe that's why this
name ;-).

BTW: You are new to the linux kernel or new to linux / unix?

Regards
Frank

-
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Re: /dev/zero

[Samuel Maftoul]

It's just zeroes, so it allows you to test raw write speed on any
device:
dd if=/dev/zero of=/dev/hda to test your performances of hda ...
normally if I get it well, /dev/zero can't be you're bottleneck.
        Sam
On Fri, Apr 12, 2002 at 08:26:22AM +0100, Rowan Ingvar Wilson wrote:
> Just as a matter of interest myself...what is it's actual function? It
> is used during kernel debugging to supply an input?
> 
> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org
> [mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Frank Schaefer
> Sent: 12 April 2002 08:19
> To: linux-kernel@vger.kernel.org
> Subject: Re: /dev/zero
> 
> On Fri, 2002-04-12 at 08:46, blesson paul wrote:
> > Hi all
> >                I am newbie to linux kernel. What is the use of
> /dev/zero. 
> > Why it is created and how to use it
> > regards
> > Blesson Paul
> > 
> > 
> > 
> > _________________________________________________________________
> > Chat with friends online, try MSN Messenger: http://messenger.msn.com
> > 
> > -
> > To unsubscribe from this list: send the line "unsubscribe
> linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> > 
> Hi,
> 
> /dev/zero is a data source. It delivers zeroes ( maybe that's why this
> name ;-).
> 
> BTW: You are new to the linux kernel or new to linux / unix?
> 
> Regards
> Frank
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel"
> in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: /dev/zero

[Guillaume Gimenez]

[-- Attachment #1: Type: text/plain, Size: 506 bytes --]

Samuel Maftoul a écrit:
    Samuel> It's just zeroes, so it allows you to test raw write speed on any
    Samuel> device:
    Samuel> dd if=/dev/zero of=/dev/hda to test your performances of hda ...
    Samuel> normally if I get it well, /dev/zero can't be you're bottleneck.
    Samuel>         Sam

Just to save Samuel's soul ;-)
the dd command supplied above will erase your primary hard drive

To see hard drive performances, hdparm -tT /dev/hda is better.

PS: Pas sympa Samuel

-- 
Guillaume Gimenez

[-- Attachment #2: Type: application/pgp-signature, Size: 190 bytes --]

Re: /dev/zero

[Samuel Maftoul]

On Fri, Apr 12, 2002 at 05:12:06PM +0200, Guillaume Gimenez wrote:
> Samuel Maftoul a écrit:
>     Samuel> It's just zeroes, so it allows you to test raw write speed on any
>     Samuel> device:
>     Samuel> dd if=/dev/zero of=/dev/hda to test your performances of hda ...
>     Samuel> normally if I get it well, /dev/zero can't be you're bottleneck.
>     Samuel>         Sam
oops really sorry, It will really earase your disk.
This morning I was really sleepy and wanted to write something other:
time dd if=/dev/zero of=/mnt/ bs=1024 count=100000 
and so you can know what's the speed not of your ide or scsi (or
something other) which is given by hdparm but it will give you the speed
through the used filesystem.
Sorry about that.
        Sam

> 
> Just to save Samuel's soul ;-)
> the dd command supplied above will erase your primary hard drive
> 
> To see hard drive performances, hdparm -tT /dev/hda is better.
> 
> PS: Pas sympa Samuel
> 
> -- 
> Guillaume Gimenez

/dev/zero

[blesson paul]

Hi
		I need some more information about /dev/zero. I need to replace the device 
driver of /dev/zero(I do not know whether I can name the program controlling 
the /dev/zero as device driver). How to do the job. If I cannot replace the 
device driver of /dev/zero, how to create a new charecter device and load my 
device driver.

regards
Blesson Paul




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Re: /dev/zero

[Frank Schaefer]

On Fri, 2002-04-19 at 10:33, blesson paul wrote:
> Hi
> 		I need some more information about /dev/zero. I need to replace the device 
> driver of /dev/zero(I do not know whether I can name the program controlling 
> the /dev/zero as device driver). How to do the job. If I cannot replace the 
> device driver of /dev/zero, how to create a new charecter device and load my 
> device driver.
> 
Hi,

I don't have any clue, why one should want to replace /dev/zero. But to
get a picture how to start writing a device driver, see
http://www.freeos.com/articles/2677/2/13/ ( Or
Goooooooooooooooooooooogle some other information ).

Regards
Frank

Re: /dev/zero

[willam]

> On Fri, 2002-04-19 at 10:33, blesson paul wrote:
> > Hi
> > I need some more information about /dev/zero. I need to replace the
device
> > driver of /dev/zero(I do not know whether I can name the program
controlling
> > the /dev/zero as device driver). How to do the job. If I cannot replace
the
> > device driver of /dev/zero, how to create a new charecter device and
load my
> > device driver.
> >
Hi,you should read the <<Linux Device Drivers>>,it will surely do good to
you.

Re: /dev/zero

[Bill Davidsen]

On Fri, 19 Apr 2002, blesson paul wrote:

> 		I need some more information about /dev/zero. I need to replace the device 
> driver of /dev/zero(I do not know whether I can name the program controlling 
> the /dev/zero as device driver). How to do the job. If I cannot replace the 
> device driver of /dev/zero, how to create a new charecter device and load my 
> device driver.

  I have to ask, WHY? Is this because you want to return a value other
than zero, to to improve the performance of /dev/zero, or just to write a
driver (/dev/one could be used ;-).

-- 
bill davidsen <davidsen@tmr.com>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

RE: /dev/zero

[Torrey Hoffman]

blesson paul wrote:
> 		I need some more information about /dev/zero. I 
> need to replace the device 
> driver of /dev/zero(I do not know whether I can name the 
> program controlling 
> the /dev/zero as device driver). How to do the job. 
...

You really ought to get yourself a copy of "Linux Device
Drivers 2nd Edition" by Rubini and Corbet.  

It contains good explanations and lots of examples.

http://www.oreilly.com/catalog/linuxdrive2/

Lucky for you, there is a free online copy:

http://www.xml.com/ldd/chapter/book/index.html

but you probably want to get the paper version too, it is
more convenient in many situations.

Good luck.

Torrey Hoffman
thoffman@arnor.net
torrey.hoffman@myrio.com