Network.Security.Tools [Electronic resources] نسخه متنی

1.10. Functions

A
function
is a block of code that performs a particular computation. Functions
can be passed input parameters and return a single value. Functions
can use arrays to return multiple values.

The following function expects the integer value
port as input. The function returns
1 if port is even,
0 if it is odd:

function is_even (port)
{
return (!(port%2));
}

The function is_even( ) performs the modulo
operation to obtain the remainder when port is
divided by 2. If the modulo operation returns 0,
the value of port must be even. If the modulo
operation returns 1, the value of
port must be odd. The
! operator is used to invert the
evaluation, and this causes the function to return
1 when the modulo operation evaluates to
0, and 0 when the modulo
operation evaluates to 1.

Functions in NASL do not care about the order of parameters. To pass
a parameter to a function, precede it with the parameter
namefor example, is_even(port:22). Here is
an example of how you can invoke is_even( ):

for(i=1;i<=5;i++)
{
display (i," is ");
if(is_even(port:i))
display ("even!");
else
display ("odd!");
display ("\n");
}

When executed, the preceding program displays the following:

1 is odd!
2 is even!
3 is odd!
4 is even!
5 is odd!

The NASL library consists of some
functions that are not
global. Such functions are defined in .inc files
and you can include them by invoking the include() function call. For example:

include("http_func.inc");
include("http_keepalive.inc");