How do I convert a binary string to a number in Perl?

Question

How can I convert the binary string $x_bin="0001001100101" to its numeric value $x_num=613 in Perl?

Answer 1

`

sub bin2dec {
    return unpack("N", pack("B32", substr("0" x 32 . shift, -32)));
}

Answer 2

Actually, I posted this for my reference and so I can point people to it when I'm asked. For reference, my preferred way is:

$x_num = oct("0b".$x_bin);

---

Quoting from man perlfunc:

oct EXPR
oct     Interprets EXPR as an octal string and returns the
        corresponding value.  (If EXPR happens to start
        off with "0x", interprets it as a hex string.  If
        EXPR starts off with "0b", it is interpreted as a
        binary string.  Leading whitespace is ignored in
        all three cases.)

Answer 3

As usual, there's is also an excellent CPAN module that should be mentioned here: Bit::Vector.

The transformation would look something like this:

use Bit::Vector;

my $v = Bit::Vector->new_Bin( 32, '0001001100101' );
print "hex: ", $v->to_Hex(), "\n";
print "dec: ", $v->to_Dec(), "\n";

The binary strings can be of almost any length and you can do other neat stuff like bit-shifting, etc.

Answer 4

Actually you can just stick '0b' on the front and it's treated as a binary number.

perl -le 'print 0b101'
5

But this only works for a bareword.