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perlpackunpack

How to print a variable in reversed byte order?

I'm trying to convert the variable $num into its reverse byte order and print it out:

my $num = 0x5514ddb7;
my $s = pack('I!',$num);
print "$s\n";

It's printing as some non-printable characters and in a hex editor it looks right, but how can I get it readable on the console? I already tried this:

print sprintf("%#x\n",$s);

This makes perl complain about a non-numeric argument, so I think pack returns a string. Any ideas how can I print out 0xb7dd1455 on the console, based on $num?

Solution

  • You need to use unpack:

    my $num = 0x5514ddb7;
my $s = pack('I<!',$num);
my $x = unpack('I>!',$s);
printf("%#x\n",$x);

    Comment from Michael Carman: Be aware that byte-order modifiers (<and >) require Perl v5.10+. For older versions of Perl you'd have to use the N and V templates instead.