perllearner has asked for the wisdom of the Perl Monks concerning the following question:

i am new to sysread. trying to get a sysread return from a display device before sending more data into it. I should be expecting from the device values in hex such as FE or FF depending on whether the buffer is full or empty. But its returning garbage characters. 

..
my $myBuf;
my $selector = IO::Select->new(\*DisplayIO);
if ($selector->can_read(3)) { # 3 second timeout.
   sysread (DisplayIO, $myBuf, 1);
   print "Buffer returned : $myBuf\n"
} else {
   print "Nothing in buffer\n";
}
..

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$myBuf is returning values such as þ & ÿ. I am hoping to get a hex return FE or FF. Thanks in advance.

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Re: sysread returning weird values
by Zaxo (Archbishop) on Jun 17, 2004 at 23:33 UTC

    You're getting what you expect: 

    $ perl -e'print ord("þ"), $/'
254
$ perl -e'print ord("ÿ"), $/'
255
$

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    After Compline,
    Zaxo

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Re: sysread returning weird values
by Ido (Hermit) on Jun 17, 2004 at 23:51 UTC
    You might want to try: 
    print "Buffer returned : ". unpack('H*',$myBuf) . "\n";

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[reply]
[d/l]

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