☜	OPEN 1977 Version of ANSI Standard					☞

3.6.12 OPEN

O[PEN] postcond L openargument

The value of the first expr of each openargument identifies a device (or "file" or "data set"). The interpretation of the value of this expr or of any exprs in deviceparameters is left to the implementor. (See 3.6.2 for the syntax specification of deviceparameters.)

The OPEN command is used to obtain ownership of a device, and does not affect which device is the current device or the value of $IO. (See the discussion of USE in 3.6.16.)

For each openargument, the OPEN command attempts to seize exclusive ownership of the specified device. OPEN performs this function effectively instantaneously as far as other processes are concerned; otherwise, it has no effect regarding the ownership of devices and the values of the device parameters. If a timeout is present, the condition reported by $T is the success of obtaining ownership. If no timeout is present, the value of ST is not changed and process execution is suspended until seizure of ownership has been successfully accomplished.

Ownership is relinquished by execution of the CLOSE command. When ownership is relinquished, all device parameters are retained. Upon establishing ownership of a device, any parameter for which no specification is present in the openparameters is given the value most recently used for that device; if none exists, an implementor-defined default value is used.

See also the transition diagram for Open.

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Copyright © Examples: 1995-2024 Ed de Moel;
Copyright © Annotations: 2003-2008 Jacquard Systems Research
Copyright © Annotations: 2008-2024 Ed de Moel.

This page most recently updated on 14-Nov-2023, 21:37:23.

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