getenv( string )
Returns the value of an environment variable given its name as the argument.
getenv ( string, number )
Returns the value of an environment variable given its name as the argument. If a second argument (number) is given and the number is zero, the function returns a string, even if the environment variable content looks like a date or a number.
nice ( number )
Lower the priority of the macro by calling the nice() system call.
putenv ( string,string )
Sets the value of an environment variable, given its name as the first argument and its value as the second argument.
shell ( ... )
Returns the exit status of the command invoked.
sleep ( number )
Stops the macro for a given number of seconds