17.1 Declarations and Parameters

Script declaration blocks are optional, and have the form

  decl {
    declarations
  }

Such a block must come before any commands in the script file. Possible declarations are:

• Parameters
• Results
• Script documentation
• Imported parameters
• Parameter groups

A parameter declaration takes the form

  param NAME : TYPE [= DEFAULT-VALUE]

where the default value is optional. Example:

  param ram_size : int = 8

This means that the variable $ram_size will be set when the script is executed, that it must be an integer, and that it will be 8 if not specified in any other way.

If there is no default value, then the parameter must be specified; otherwise, it is optional.

A script with a declaration block will only see the variables that have been declared as parameters. Other variables are hidden during the script's execution and will re-appear when the script terminates.