Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!ncar!tank!uxc!uxc.cso.uiuc.edu!uicsrd.csrd.uiuc.edu!kai
From: kai@uicsrd.csrd.uiuc.edu
Newsgroups: comp.unix.wizards
Subject: Re: Accessing a VAX tape drive from a S
Message-ID: <43200036@uicsrd.csrd.uiuc.edu>
Date: 8 Sep 88 05:17:00 GMT
References: <711@auvax.UUCP>
Lines: 18
Nf-ID: #R:auvax.UUCP:711:uicsrd.csrd.uiuc.edu:43200036:000:909
Nf-From: uicsrd.csrd.uiuc.edu!kai    Sep  8 00:17:00 1988


>/* Written  7:58 pm  Sep  6, 1988 by chris@mimsy.UUCP in uicsrd.csrd.uiuc.edu:comp.unix.wizards */
>`dd' can indeed do the trick, but not with the options you gave.  With
>just a `bs' option and no conversions, dd defaults to copying the input
>record size to its output, so that if it reads 32, then 1024, then 12
>bytes, it writes 32, then 1024, then 12 bytes.
>	dd bs=N
>and
>	dd ibs=N obs=N
>have different meanings.

With NO options, dd just copies input to output.  If you specify "bs=20b", or
"ibs=20b obs=20b", dd reads and writes 10240 byte blocks from input to
output.  Sorry, but these two parameter settings are the same, except that
using "bs" to specify both input and output buffer sizes is more efficient,
since copying between buffers need not be done, unless you are doing ASCII to
EBCDIC conversions or some other type of data conversion.

Patrick Wolfe  (pwolfe@kai.com, kailand!pwolfe)