Comments In expect Commands
It is tempting to add comments after patterns and actions. However, it cannot be done arbitrarily. For example, the following example does not do what was intended.
expect { "orange" squeeze_proc ;# happens every morning "banana" peel_proc }
The problem in this code fragment is that the comment occurs in a place where the expect
command is expecting patterns and actions. The expect
command does not have any special way of handling comments. In this example, the expect
command simply assumes that ";#
" is a pattern and happens
is the associated action. every
and morning
are also interpreted as a pattern and action.
This particular comment is rather lucky. The pattern banana
is still used as a pattern. However, if the comment had one more word in it, banana
would be used as an action and peel_proc
as a pattern!
Remember that comments behave a lot like commands.[31] They can only be used where commands can be used. If you want to associate a comment with an action, then use braces to create a list of commands and embed both the comment and the action within the list. In the following fragment, all of the comments are safe.
expect { "orange" { # comments can appear here safely, too squeeze_proc ;# happens every morning # comments can appear here safely, too } "banana" peel_proc }
[31] The only significant difference between comments and commands is that arguments of a comment are not evaluated.
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