DEVRESERV(8) Maintenance Commands and Procedures DEVRESERV(8)

NAME

devreserv - reserve devices for exclusive use

SYNOPSIS

devreserv [key [device-list]...]

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 device-list. 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.

OPERANDS

The following operands are supported:

device-list
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.


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

EXAMPLES

Example 1: Reserving a Floppy Disk and a Cartridge Tape

The following example reserves 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

Example 2: Listing All Devices Currently Reserved

The following example lists all devices currently reserved:


$ devreserv
disk1 2423
diskette1 10658
ctape1 10658

Example 3: Listing All Devices Currently Reserved to a Particular Key

The following example lists all devices currently reserved to a
particular key:


$ devreserv $key
diskette1
ctape1

EXIT STATUS

The following exit values are returned:

0
Successful completion.


1
Command syntax was incorrect, an invalid was option used, or an
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

SEE ALSO

attributes(7), devfree(8)

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. 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.

July 5, 1990 DEVRESERV(8)