DEVRESERV(8) Maintenance 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)