How do I get a checksum from unpack in hexadecimal format?

I've been trying to figure out the unpack function in Perl and can't quite figure out the whole thing.

What I have: A string and a 16-bi开发者_Go百科t hex checksum (e.g. "this is my string", "0671")

I need to check that "this is my string" equals the checksum '0671'.

So I know unpack("%16W*", $string) will give me the 16-bit decimal value, but I need the hex representation. I know this is an easy one so please forgive my ignorance.

As you said, unpack("%16W*", $string) gives you an integer. To convert an integer to hex, use sprintf:

my $string = "this is my string";
my $expected = '0671';

my $checksum = sprintf('%04x', unpack("%16W*", $string));
print "match\n" if $checksum eq $expected;

If you want upper-case hex digits, use %X instead of %x (or %04X in this case).

Or, you could go the other way and convert your hex checksum to an integer using hex:

my $string = "this is my string";
my $expected = '0671';

my $checksum = unpack("%16W*", $string);
print "match\n" if $checksum == hex $expected; # now using numeric equality

Try unpack("b*',$string).

See the pack man page for syntax.