devreserv(1M)         UNIX System V(Essential Utilities)          devreserv(1M)


NAME
      devreserv - reserves devices for exclusive use

SYNOPSIS
      devreserv [pid [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 pid it was reserved.  When
      devreserv is invoked with only the pid argument, it lists the devices
      that currently reserved to that process id.

      The arguments for this command are:

      pid       Designates the application's process id number on which the
                device will be reserved.

      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 diskett1,ctape1
            /dev/dsk/f0t
            /dev/rmt/c0s0

      To list all devices currently reserved:

            $ devreserv
            disk1         2423
            /dev/dsk/f0t
            /dev/rmt/c0s0

      To list all devices currently reserved to a particular key:

            $ devreserv $key
            /dev/dks/f0t
            /dev//rmt/c0s0



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devreserv(1M)         UNIX System V(Essential Utilities)          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.  The pid argument must be the process
      id of the controlling process.  This process should be active both when
      the device is reserved and when it is freed.  When a process becomes
      inactive, all devices reserved to the process id are canceled by the
      system.

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




















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