When a DataHub instance executes a command, it may return a success message or an error message. The returned message contains the original command, and some or all of the arguments for the command. These messages will be received by programs connected to the DataHub instance, but they will not be received by DataHub scripts. The two types of success messages are:
No arguments
(success
command)
One or more arguments
(success
command
arg1)
Success messages are returned if the DataHub command acksuccess has been
previously issued with a value of 1. A value of
0 means no success messages will be returned. Error messages
are returned any time there is an error. There are four types of error
messages:
No arguments
(error "-2: (
command):
error message")
One argument
(error "-2: (
command
arg1):
error message")
Two arguments
(error "-2: (
command
arg1
arg2):
error message")
More than two arguments
(error "-2: (
command
arg1 ...):
error message")
The error messages are the negation of these error codes:
ST_OK
| The function executed without error. |
ST_ERROR
| An error occurred. |
ST_NO_TASK
| A required task does not exist. |
ST_NO_MSG
| There is no message available. |
ST_WOULDBLOCK
| This action would block, and is not permitted. |
ST_INTR
| An interrupt occurred. |
ST_FULL
| The queue is full. |
ST_LOCKED
| A DataHub point is locked. |
ST_SECURITY
| The security level is insufficient. |
ST_NO_POINT
| A required DataHub point does not exist. |
ST_INSIG
| A change in a DataHub point value is insignificant. This is not really an error, but a notification that no exception will be generated by the DataHub instance. |
ST_UNKNOWN
| There is an unknown error. |
ST_NO_QUEUE
| A target task has no queue, or qserve is absent. |
ST_CMD_SYNTAX_ERROR
| The command was not found, or there was a syntax error. |
ST_REPLIED
| The reply was complete. |
ST_WRONG_TYPE
| The type of a point or variable was wrong. |
ST_TOO_LARGE
| A value to be written to memory is larger than the available buffer. |
ST_NO_MEMORY
| There is insufficient memory available. |
ST_OLD_DATA
| Time-significant data is out of date. |
ST_TIMEOUT
| A timeout occurred in poll mode. |