What are Constants?

Like variables, constants are used to identify data in a task. However, unlike a variable, a constant is an identifier whose associated value is "fixed," therefore, it cannot typically be altered by a task during its execution. The elements of a constant consists of a name and value. A constant's defined value is global, thus, are available to all tasks on a particular system. When you modify a constant's value, every occurrence of that value is updated across the system.

Constants are useful for defining values that are used often but may change over time or modifying multiple instances of a value at one time. For example, you could create a constant named AdminEmail and assign the network administrator's email address as the value. You could use this constant in multiple tasks where you wanted to send an e-mail notification to the network administrator. If you wanted to run such a task at another location with a different network administrator, you would set up a constant of the same name at the other location and assign it whatever value you wanted. If the network administrator's e-mail address changed, you would simply change the value of the constant.

Using Constants

Constants may be used in any step parameter by specifying the name of the constant surrounded by percent (%) signs. For example, if a constant named BackupFolder was initially created and given the value of an existing directory used to normally backup files, specify this directory as the destination in a Copy File action, and enter %BackupFolder% in the  Destination parameter of this action.

To add a constant in an action using the Expression Builder

  1. In the Properties dialog of an action, click inside any entry box then click Insert Expression/Variable which appears next to any entry box that accepts expressions.

  2. In the Expression Builder window that appears, select the folder labeled Constants from the list of folders located in the bottom left pane.

  3. Double-click a selection from the list of the defined constants for the local machine that are populated in the bottom right pane. This populates the top pane with the selected item. The selected item will be automatically surrounded with percent signs upon insertion, therefore, there is no need to surround the item with percent signs at this point.

  4. Click Insert to properly insert the constant and close the Expression Builder window. For further information, refer to "Using the Expression Builder" in the Automate Desktop help.