Obtaining operation results

The start_waitable_operation command returns a unique operation handle, which can be passed to the following command to obtain the results of the operation:

wait_for_operation operationHandle

This function will return the results of the operation in the following formatted string:

status returnValue1 [returnValue2 [returnValue3 [...]]]

The status field will contain one of the following:

• normal

  This is returned if the operation has completed without any errors, and the return arguments are valid.

• update

  This indicates that an update from the operation has been received. There may be arguments that can be used as intermediate results (e.g. for graphing individual points as the operation proceeds). The update message may also be used as a trigger to perform another operation.

  A status of update indicates that the operation is not yet completed. It is necessary to issued the wait_for_operation command again until the status changes to normal.

• An error message

  Any string other than normal or update in the status field indicates that an error has occurred in the operation.

  The wait_for_operation command will return a TCL level error which must be caught (using the TCL catch command) if the script writer intends to do any clean up. If the error is not caught, the currently running operation or scripted device will return an error condition.

  See Exception handling for details on handling errors.

It is not necessary to worry about the exact timing of the wait_for_operation command. If the wait_for_operation command is issued after the operation has already completed, the results of the operation will be returned by the scripting engine immediately. If the command is issued before the operation is completed, the script will hang until the operation is completed or the operation sends an update message.

Example: Waiting for the results of the optimize operation

	set opHandle [start_waitable_operation optimize table_vert i2 20 0.05 0.1] 
	set result [wait_for_operation $opHandle]
	log_note $result

output: normal 30.774772