3.9 Using Variables

As any programming language, MFL has a concept of variables. A variable is declared using the following syntax:

type name

where variable is the variable name and type defines its type: either string, or number.

A variable is assigned a value using the set statement:

set name expr

where expr is any valid MFL expression.

The set statement can occur within handler or function declarations as well as outside of them.

A variable need not be declared prior to assigning a value: a set statement with name referring to a variable that has not been declared, declares it implicitly, deducing its type from that of the expr.

There are two kinds of Mailfromd variables: global variables, that are visible to all handlers and functions, and automatic variables, that are available only within the handler or function where they are declared. Any variable declared outside of a prog block is a global variable. Global variables are used to pass information between the handlers. For example, the following code fragment uses global variable helohost to store the argument to the helo handler and to use it later on to decide whether to accept the message.

# Declare the helohost variable
string helohost

prog helo
do
  # Save the host name for further use
  set helohost $1
done

prog envfrom
do
  # Reject hosts claiming to be localhost
  if helohost = "localhost"
    reject 570 "Please specify real host name"
  fi
done