1.9. Loops
Loops
are used to
iterate through a particular set of statements based upon a set of
conditions. The following sections discuss the different types of
loop statements supported by NASL.
1.9.1. for
A for loop expects three statements separated by
semicolons as arguments. The first statement is executed first, and
only once. It is most frequently used to assign a value to a
variable, which is usually used by the loop to perform iteration. The
second statement is a condition that should return
true for the loop to continue looping. The third
statement is invoked by the for loop after every
iteration, and is used to increment or decrement the iteration
variable. For example, the following for loop
prints all the values of the array myports:for(i=0; i < max_index(myports); i++)
{
display(myports[i],"\n");
} The function max_index() returns the number of elements in an
array, and we use it in our
for loop to ensure that the value of
i is within range.
1.9.2. foreach
You can use the foreach statement to loop for every
array element. This is useful in cases when you need to iterate
through an array. For example, the following loop iterates through
myports[] and prints the values contained in it:foreach i (myports)
{
display (i, "\n");
}
1.9.3. repeat...until
The condition specified after until is evaluated
after the loop is executed. This means a
repeat...until loop always executes at least once.
For example, the following displays the string
Looping!:i=0;
repeat
{
display ("Looping!\n");
} until (i == 0);
1.9.4. while
A while loop expects one conditional statement and
loops as long as the condition is true. For example, consider the
following while loop, which prints integers 1 to
10:i=1;
while(i <= 10)
{
display(i, "\n");
i++;
} |
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