Conditions for executing commands Sample Clauses

Conditions for executing commands. We’ve already seen many examples of specifying specific conditions for the ex- ecution of an event. You can also specify conditions for executing a command, using the If command. This command takes three arguments; the first one is a condition, the second is a command to be executed if the condition is satisfied, and the third is a command to be executed if the condition is not satisfied. Each of the arguments must be surrounded by quotes to indicate that it should be treated as a unit. Here’s a simple example of how the If command might be used. Assume that correct and errors are counters. This will increase the value of the counter correct if the key pressed is the correct key, otherwise it will increase the value of the counter errors. If "$key equals $correct_key" "Increment $correct" "Increment $errors" Note that the third argument is optional; if it is omitted, nothing will be done if the condition isn’t satisfied. The If command is often combined with a command event; see Section 4.12.