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From: andyd@pogo.WV.TEK.COM (Andy Davidson)
Newsgroups: comp.lang.perl
Subject: Unpack checksum doesn't match BSD sum
Message-ID: <10911@pogo.WV.TEK.COM>
Date: 19 May 91 22:55:08 GMT
Reply-To: andyd@pogo.WV.TEK.COM (Andy Davidson)
Distribution: na
Organization: Tektronix, Inc., Wilsonville,  OR.
Lines: 43


Newsgroups: comp.perl
Subject: unpack & checksum
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Reply-To: andyd@pogo.WV.TEK.COM (Andy Davidson)
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I am trying to use the snippet of code in the man page to use the unpack
function to generate a 16-bit checksum, i.e.,

        while (<>) {
            $checksum += unpack("%16C*",$_);
        }
        $checksum %= 65536;
        printf "%ld\n", $checksum;

I also tried the version shown in the Camel book:

        undef $/;
        $checksum = unpack("%16C*", <>);
        printf "%ld\n", $checksum;

However, these report different results than sum does, either on my 4.3BSD
VAX or a Sun running SunOS 4.1.  Why?  Is there a difference between what
System V 'sum' reports and what BSD 'sum' reports?  Or am I doing something
wrong?

I am currently running version 4.0 patchlevel 3.

        andy

        

-- 
    Andy Davidson    503-685-3033        Manager, Tektronix/GPID QA & Tools   
       Internet: andyd@pogo.WV.tek.com     uucp: ...!tektronix!pogo!andyd
                        Trust, but verify!