Xref: utzoo comp.unix.questions:5360 comp.unix.wizards:6337 comp.unix.xenix:1396
Path: utzoo!mnetor!uunet!husc6!linus!gatech!ugacs!hal
From: hal@ugacs.UUCP (Hal N. Brooks)
Newsgroups: comp.unix.questions,comp.unix.wizards,comp.unix.xenix
Subject: Re: chksum in tar header block
Message-ID: <343@ugacs.UUCP>
Date: 27 Jan 88 14:37:38 GMT
References: <243@mancol.UUCP>
Reply-To: hal@ugacs.UUCP (Hal N. Brooks)
Organization: Univ. of GA, CS Dept.
Lines: 40
Keywords: tar,header,chksum



In Message-ID: <243@mancol.UUCP> samperi@mancol.UUCP writes:

>  Can somebody explain how the chksum in a tar header block is computed? ...
>  I can't seem to compute a checksum by hand that agrees with the
>  figure displayed (using od -c for the dump). ...

and spaf replies:

>  Look in section 5 of your manual, at the entry that describes the
>  tar tape format.  It explains how the checksum is calculated.

I found that our AT&T System V documentation didn't include the tar(5)
page, so I had to rely on tar(5) from someone else's Ultrix manual.  At
any rate, you seem to already have access to this information.

The discrepancy I noted was that this manual page stated:

   "`Chksum' is a decimal ASCII value ..."

when it SHOULD have said:

   "`Chksum' is an OCTAL ASCII value ..."

Actually I shouldn't say `should', since I was using header documentation
belonging to a different system.

I have no comments on XENIX.

Let me know if this works for you.


-hal    (...gatech!ugacs!hal)

Hal Brooks
Univ. of Ga.
CS Dept. Systems Support

No warranty is expressed or implied.