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From: mats@forbrk.UUCP (Mats Wichmann)
Newsgroups: comp.unix.wizards
Subject: Re: Size of SysV "block"
Message-ID: <348@forbrk.UUCP>
Date: Tue, 30-Jun-87 09:44:42 EDT
Article-I.D.: forbrk.348
Posted: Tue Jun 30 09:44:42 1987
Date-Received: Sat, 11-Jul-87 01:43:08 EDT
References: <218@astra.necisa.oz>
Reply-To: mats@forbrk.UUCP (Mats Wichmann)
Distribution: world
Organization: Fortune Systems / SCI Technology  (Berkeley, CA)
Lines: 23
Keywords: blocks sectors

In article <218@astra.necisa.oz> dave@astra.necisa.oz (Dave Horsfall) writes:
>Can anyone tell me in an unambiguous manner just how many bytes
>are in the following System V (2.?) "blocks"? 

>	ls -s   du   df   tar -b   cpio -B   mkfs   fsck   fsdb
All of the preceding are 512 byte "blocks" and refer to "disk" blocks;
it is left at 512 to avoid having to change things around on systems which
support different logical block sizes on different file systems and just
for general consistency (let's see, this is a Frozzboz 1000, the blocks must
875 bytes each, unlike the 1500, where they are 950 each...).

>	BUFSIZ
This is the stdio buffer size and varies from system to system, although
it seems to be 1024 for most V.2 implementations - should be the same size 
as the largest allowable file system logical block.

Note that there are programs, such as CPIO, which take an argument (-B
in the case of cpio) which seems to indicate that the block size is
changed; really this sets the "blocking factor" - how many blocks to
collect before doing the physical write/read. The number reported by
cpio when it finishes is still in terms of 512-byte blocks.

Mats Wichmann