topic Re: what is the /dev/zero at all? in Operating System - Linux

what is the /dev/zero at all?

frederick van tagero — Tue, 08 Apr 2003 05:15:52 GMT

thanks, i do not know what it is.

Best Regards,
Frederick

Re: what is the /dev/zero at all?

Balaji N — Tue, 08 Apr 2003 05:33:18 GMT

man zero.

it is the same as /dev/null.

++++++++++++++++++++++++++++++
DESCRIPTION
Data written on a null or zero special file is discarded.

Reads from the null special file always return end of file, whereas
reads from zero always return \0 characters.

null and zero are typically created by:

mknod -m 666 /dev/null c 1 3
mknod -m 666 /dev/zero c 1 5
chown root:mem /dev/null /dev/zero

NOTES
If these devices are not writable and readable for all users, many pro-
grams will act strange.
++++++++++++++++++++++++++++++

-balaji (and i love answering ur questions. for i get easy bunnies)

Re: what is the /dev/zero at all?

Balaji N — Tue, 08 Apr 2003 05:37:47 GMT

a small correction. they are similar files rather than telling the same.

-balaji

Re: what is the /dev/zero at all?

Michael Steele_2 — Tue, 08 Apr 2003 12:21:12 GMT

/dev/zero is used to sanitize your disk. If you are returning leased equipment or even throwing away a computer then some people worry about an invasion of privacy from scavengers who pull confidential information off of these disks.

dd if=/dev/zero if=/dev/dsk/cXtYdZ bs=32

Re: what is the /dev/zero at all?

Sergejs Svitnevs — Tue, 08 Apr 2003 13:06:17 GMT

Think of /dev/null as a "black hole". It is the nearest equivalent to a write-only file. Everything written to it disappears forever. Attempts to read or output from it result in nothing. Nevertheless, /dev/null can be quite useful from both the command line and in scripts.

Regards,
Sergejs

Re: what is the /dev/zero at all?

Stuart Browne — Wed, 09 Apr 2003 00:22:49 GMT

What's been said so far is right on the money.

Some classic examples of what they are used for:

/dev/null

some.application 2>/dev/null

To redirect errors to the bit-bucket, so you don't see them on the screen.

/dev/zero

dd if=/dev/zero of=some.file bs=1024b count=1024

Create a completely empty 1MB file. Creating test files to do work on is not all that unusual. Some times people use this to check if their file-system can create large-files (greater than 2GB).

It can also be used to clean a disk (whether it be a floppy or a hard-disk) as mentioned in an earlier post.

anyway.. hope this clears things up a bit.

Re: what is the /dev/zero at all?

Donald Kok — Wed, 09 Apr 2003 10:17:30 GMT

Hi,

In my opinion /dev/zero is different than /dev/nul.

/dev/zero can produce an (virtual) endless stream of zero's, where /dev/nul is just a bitbucket.

Greetzz
Donald

Re: what is the /dev/zero at all?

Stuart Browne — Wed, 09 Apr 2003 22:01:29 GMT

*points to Balaji's second post* yup..