I have a simple script that appears to show that some byte in the output is causing Perl to behave strangely.

The script calls a command that coughs up 150 bytes or so of binary data. One stream of returned data behaves as expected. Another stream causes chaos.

The script:

$cmd = "/usr/local/bin/mycmd";
print "The cmd to be run is: $cmd \n";
open(CMD, "$cmd |" ) or die "Can't run '$cmd'\n$!\n";
while (<CMD>)
    {
    chomp;
    print "My raw output is: $_ \n";
    $dataout = $_;
    print "My DATAOUT is: $dataout \n";
        }

[download]

When I run the above script in a "good" scenario I get the below output:

The cmd to be run is: /usr/local/bin/mycmd
My raw output is:  &#65533; ` /11&#65533;%_$&#65533;%f$&#65533;&c$&#65
+533;%a$&#65533;%\$&c$&^$&#65533;&i$
My DATAOUT is: &#65533; ` /11&#65533;%_$&#65533;%f$&#65533;&c$&#65533;
+%a$&#65533;%\$&c$&^$&#65533;&i$

[download]

When I run the above script in a "bad" scenario I get the below output:

The cmd to be run is: /usr/local/bin/mycmd
My raw output is:
My DATAOUT is: 
My raw output is: &#65533;0]&#65533;c &#65533;&#65533;
My DATAOUT is: &#65533;0]&#65533;c &#65533;&#65533;

[download]

Ultimately the goal is to ingest the data and process it using unpack but that was failing as $_ didn't contain data is should contain to process. The "bad" behavior above seems to show that there is some sort of "killer byte" being output from mycmd that throws a wrench into things. Below is the good and bad output in hex form via xxd. Is there a byte in there tripping up Perl?

Good data stream:

0000000: 0202 00d0 0000 0000 0000 0000 0100 0000  ................
0000010: 0100 0000 0100 0000 0100 0000 0100 0000  ................
0000020: 0100 0000 0100 0000 0500 0000 0500 0000  ................
0000030: 0500 0000 0500 0000 0500 0020 0100 0000  ........... ....
0000040: 0100 0000 0100 0000 0100 0000 0100 0000  ................
0000050: 0100 0000 0100 0000 0500 0000 0500 0000  ................
0000060: 0500 0000 0100 0000 0100 0000 0000 0000  ................
0000070: 0200 0060 0100 0020 0000 0000 0100 2d00  ...`... ......-.
0000080: 0100 2f00 0100 3000 0000 0000 0100 0000  ../...0.........
0000090: 0000 0000 0102 ca25 0102 4a24 0102 bd25  .......%..J$...%
00000a0: 0102 5024 0102 da25 0102 4c24 0102 d525  ..P$...%..L$...%
00000b0: 0102 4c24 0102 c325 0102 4624 0102 e025  ..L$...%..F$...%
00000c0: 0102 4e24 0102 e225 0102 4824 0102 dd25  ..N$...%..H$...%
00000d0: 0102 5224                                ..R$

[download]
Bad data stream:

0000000: 020a 009c 0000 0000 0000 0000 0100 0000  ................
0000010: 0100 0000 0100 0000 0100 0000 0100 0000  ................
0000020: 0100 0000 0100 0000 0100 0000 0500 0000  ................
0000030: 0500 0000 0500 0000 0500 0000 0500 0000  ................
0000040: 0500 0000 0500 0000 0500 0000 0500 0000  ................
0000050: 0500 0000 0500 0000 0500 0000 0500 0000  ................
0000060: 0500 0000 0500 0000 0100 0000 0000 0000  ................
0000070: 0100 3000 0000 0000 0100 005c 0100 00b4  ..0........\....
0000080: 0000 0000 0100 0000 0000 0000 0200 0063  ...............c
0000090: 0100 0020 0000 0000 0103 9206 0103 8506  ... ............

[download]

In reply to Killer byte tripping up Perl? by echo5

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.