devreserv(1M)                  DG/UX 5.4R3.00                  devreserv(1M)


NAME
       devreserv - reserve devices for exclusive use

SYNOPSIS
       devreserv [key [devicelist [...]]]

DESCRIPTION
       devreserv reserves devices for exclusive use.  When the device is no
       longer required, use devfree to release it.

       devreserv reserves at most one device per devicelist.  Each list is
       searched in linear order until the first available device is found.
       If a device cannot be reserved from each list, the entire reservation
       fails.

       When devreserv is invoked without arguments, it lists the devices
       that are currently reserved and shows to which key it was reserved.
       When devreserv is invoked with only the key argument, it lists the
       devices that are currently reserved to that key.

       The arguments for this command are:

       key       Designates a unique key on which the device will be
                 reserved.  The key must be a positive integer.

       devicelist
                 Defines a list of devices that devreserv will search to
                 find an available device.  (The list must be formatted as a
                 single argument to the shell.)

EXAMPLE
       To reserve a floppy disk and a cartridge tape:

            $ key=$$
            $ echo "The current Process ID is equal to: $key"
            The Current Process ID is equal to: 10658
            $ devreserv $key diskette1 ctape1

       To list all devices currently reserved:

            $ devreserv
            disk1         2423
            diskette1     10658
            ctape1        10658

       To list all devices currently reserved to a particular key:

            $ devreserv $key
            diskette1
            ctape1

DIAGNOSTICS
       The command will exit with one of the following values:




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devreserv(1M)                  DG/UX 5.4R3.00                  devreserv(1M)


       0 = successful completion of the task.

       1 = command syntax incorrect, invalid option used, or internal error
           occurred.

       2 = device table or device reservation table could not be opened for
           reading.

       3 = device reservation request could not be fulfilled.

FILES
       /etc/device.tab
       /etc/devlkfile

NOTES
       The commands devreserv and devfree are used to manage the
       availability of devices on a system.  Their use is on a participatory
       basis and they do not place any constraints on the actual access to
       the device.  They serve as a centralized bookkeeping point for those
       who wish to use them.  To summarize, devices which have been reserved
       cannot be used by processes which utilize the device reservation
       functions until the reservation has been canceled.  However,
       processes that do not use device reservation may use a device that
       has been reserved since such a process would not have checked for its
       reservation status.

SEE ALSO
       devattr(1M), devfree(1M), getdev(1M), putdev(1M).





























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