devreserv(1M)                                                 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 ctape1

         To list all devices currently reserved:

               $ devreserv
               disk1         2423
               ctape1        10658

         To list all devices currently reserved to a particular key:

               $ devreserv $key
               ctape1





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   devreserv(1M)                                                 devreserv(1M)


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

         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
         devfree(1), devfree(3X), devreserv(3X), reservdev(3X).






















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