NAME

devreserv - reserve devices for exclusive use

SYNOPSIS

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

DESCRIPTION

devreserv reserves devices for exclusive use.  When the dev-
ice  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

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 inter-
    nal 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).