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Editorial Team
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Asked: 2026-06-06T15:01:02+00:00

I’d like to write a parsing script in Perl that prints all the interface

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I’d like to write a parsing script in Perl that prints all the “interface name” from these bunch of data:

interfaces.ifTable.ifEntry.ifDescr.1 : OCTET STRING- (ascii): (hex): length = 30
    0:  53 6f 66 74 77 61 72 65 20 4c 6f 6f 70 62 61 63     Software Loopbac
    16:  6b 20 49 6e 74 65 72 66 61 63 65 20 31 00 -- --     k Interface 1...

interfaces.ifTable.ifEntry.ifDescr.2 : OCTET STRING- (ascii): (hex): length = 20
    0:  57 41 4e 20 4d 69 6e 69 70 6f 72 74 20 28 53 53     WAN Miniport (SS
    16:  54 50 29 00 -- -- -- -- -- -- -- -- -- -- -- --     TP).............

interfaces.ifTable.ifEntry.ifDescr.3 : OCTET STRING- (ascii): (hex): length = 20
    0:  57 41 4e 20 4d 69 6e 69 70 6f 72 74 20 28 4c 32     WAN Miniport (L2
    16:  54 50 29 00 -- -- -- -- -- -- -- -- -- -- -- --     TP).............

I’d like to extract all the three interfaces’ name out, as (“Sotware Loopback Interface 1”, “WAN Miniport (SSTP)”, “WAN Miniport (L2TP)”), and do further processing. I tried using regular expression but without luch. Is there any simple way to do this? Thanks in advance!

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1 Answer

  1. Editorial Team

    This is yet another dirty perl script. Read your data into $text however you wish. The regular expression looks for the pattern of each hex dump line. The join line then recombines the hex values back into the string and appends it to the current accumulated interface name. mttrb’s is simpler. 😉

    $text =<<EOM;
interfaces.ifTable.ifEntry.ifDescr.1 : OCTET STRING- (ascii): (hex): length = 30
    0:  53 6f 66 74 77 61 72 65 20 4c 6f 6f 70 62 61 63     Software Loopbac
    16:  6b 20 49 6e 74 65 72 66 61 63 65 20 31 00 -- --     k Interface 1...

interfaces.ifTable.ifEntry.ifDescr.2 : OCTET STRING- (ascii): (hex): length = 20
    0:  57 41 4e 20 4d 69 6e 69 70 6f 72 74 20 28 53 53     WAN Miniport (SS
    16:  54 50 29 00 -- -- -- -- -- -- -- -- -- -- -- --     TP).............

interfaces.ifTable.ifEntry.ifDescr.3 : OCTET STRING- (ascii): (hex): length = 20
    0:  57 41 4e 20 4d 69 6e 69 70 6f 72 74 20 28 4c 32     WAN Miniport (L2
    16:  54 50 29 00 -- -- -- -- -- -- -- -- -- -- -- --     TP).............
EOM

$interface = "";
foreach $line (split(/\n/, $text)) {
  next unless $line =~ /\b(\d+):\s+((?:[0-9a-fA-F-]{2} ){16})/;
  if ($1 == 0) {
    print "$interface\n" if $interface;
    $interface = "";
  }
  $interface .= join('', map { chr(hex($_)) } grep { $_ ne '--' && $_ ne '00' } split(/ /, $2));
}
print "$interface\n" if $interface;

    To explain the join line, the following things occur in that line.

    1. split(/ /, $2) – Takes the second saved group from the regular expression, which are the hex characters, and splits it into an array containing each pair of digits.
    2. grep { $_ ne ‘–‘ && $_ ne ’00’ } – Looks through the digit pair array and filters out the ‘–‘ and ’00’ entries, leaving only valid values.
    3. map { chr(hex($)) } – Runs the expression against each of the filtered pairs, $ being the pair being processed. Hex parses it from a hex() string into a number and then chr() takes that number and translates it into the corresponding character.
    4. join(”, …) – Takes in the array of characters that map created and creates a single string out of them. The ” is the string to separate each array item with, in this case nothing.
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