Function to test for number?

Anon

Does anyone know how I can test if a form input is in the form of a number?

For example, I'm passing port=3000 to the PHP program. When I access $port, I want to test whether the user has actually entered a number or an invalid alphanumeric input.

Any ideas?

thanks for helping,
Sridhar

Anon

  if (ereg("^[0-9]+$", $input))

tests if the variable $input contains exactly one or more digits.
You may also want to limit the length to ensure the number
string doesn't overflow when converted to numeric. For
port numbers, you want to keep in the range 1..65535 I
assume:

  if (ereg("^{[0-9]{1,5}$",} $input))
    {
    $input = (int) $input;
    if ($input < 1 || $input > 65535)
      complain();
    }

Anon

(kirk, thanks for replying)

I always though 65535 was the highest port number a computer can bind/connect to. But I was proved wrong. I have an sun station with solaris 2.8, debian 2.2 and redhat 6.2 and its has a 64-bit ultrasparc-60 processor.

I wrote a small C program (under redhat) and i 'bind'ed to port ... 1231212, and it successfully worked. I also tried to connect to this port using a client script. It worked.

does anyone know the greatest port number on my system type?

-Sridhar

Anon

Nope, IP v4 port numbers are definitely 16-bit. What's
probably happening is that the number is being truncated
to a 'unsigned short' value by taking the lower 16 bits,
and you're just getting lucky that the resulting port is
unused and thus available to your process.

Anon

thanks for replying...
i understand the situation....

under any protocol, can a port number be greater than 2^16?