AppleScript: The Definitive Guide, 2nd Edition

With

A with block is used to specify certain external attributes of Apple events sent to target applications from inside the block. Two types of with block are defined: a timeout block and a transaction block.

Timeout

Recall from "Apple Events" in Chapter 3 that during interapplication communications, the sender of an Apple event may attach to that Apple event a specification of how long it is willing to wait for a reply. This is the Apple event's timeout period. If the target does not reply within the specified timeout period, for whatever reason (the requested operation might be too lengthy, the target application might be otherwise engaged, and so forth), the system stops waiting for a reply and reports to the sender that the Apple event timed out. This report arrives as an error; your script can handle this error and proceed (see "Errors," later in this chapter).

This entire mechanism is valuable, because (among other things) it rescues the sender from hanging indefinitely while waiting for the target to reply; if the target takes too long, the sender is able to proceed nonetheless. Of course, the sender must then do without any reply from the target, but a script can take account of this possibility. For example, reporting the problem to the user and proceeding, or even terminating in good order, is surely preferable to hanging or appearing to hang while waiting for a reply that is taking a long time to arrive and that may, indeed, never come.

All Apple events sent to target ...