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Owning Palette: Semaphore VIs

Installed With: Base Package

Obtains a reference to an existing semaphore or creates a new semaphore and returns a reference to that semaphore.

You can use the reference when you call other Semaphore VIs.

Details  Example

	name contains the name of the semaphore you want to look up or create. The default is an empty string to create an unnamed semaphore. If you wire name, LabVIEW searches for an existing semaphore with the same name and returns a unique reference to the existing semaphore. If a semaphore with the same name does not already exist and create if not found is TRUE, LabVIEW creates a new, named semaphore and returns a unique reference to that semaphore.
	size specifies how many tasks can acquire the semaphore at the same time. If a named semaphore already exists, wiring a value to this parameter does not resize the semaphore. size must be greater than or equal to 1. The default is 1.
	create if not found specifies whether you want to create a new semaphore if one with that name does not exist. The default is TRUE, which specifies that LabVIEW creates a semaphore if the semaphore does not exist. If create if not found is FALSE and LabVIEW cannot find a semaphore with the name you specify, LabVIEW returns error code 1534.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use exception control to treat what is normally an error as no error or to treat a warning as an error. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	semaphore is a reference to an existing or newly created semaphore. If you use this VI to obtain multiple references to the same named semaphore, each reference number is unique.
	created new is TRUE if the VI created a new semaphore.
	error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

Obtain Semaphore Reference Details

You cannot use semaphores to communicate between LabVIEW application instances. If you obtain a reference to a semaphore in one application instance, you cannot use that semaphore reference in another application instance.

Example

Refer to the Semaphore with SubVIs VI in the labview\examples\general\semaphore.llb for an example of using the Obtain Semaphore Reference VI.