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GuruMeditation
Docs » Autodocs » exec.library » OpenDevice

NAME

	OpenDevice -- gain access to a device

SYNOPSIS

	error = OpenDevice(devName, unitNumber, iORequest, flags)
D0 A0 D0 A1 D1
BYTE OpenDevice(STRPTR,ULONG,struct IORequest *,ULONG);

FUNCTION

	This function opens the named device/unit and initializes the given
I/O request block. Specific documentation on opening procedures
may come with certain devices.
The device may exist in memory, or on disk; this is transparent to
the OpenDevice caller.
A full path name for the device name is legitimate. For example
"test:devs/fred.device". This allows the use of custom devices
without requiring the user to copy the device into the system's
DEVS: directory.

NOTES

	All calls to OpenDevice should have matching calls to CloseDevice!
Devices on disk cannot be opened until after DOS has been
started.
As of V36 tasks can safely call OpenDevice, though DOS may open
system requesters (e.g., asking the user to insert the Workbench
disk if DEVS: is not online). You must call this function from a
DOS Process if you want to turn off DOS requesters.

INPUTS

	devName - requested device name
unitNumber - the unit number to open on that device. The format of
the unit number is device specific. If the device does
not have separate units, send a zero.
iORequest - the I/O request block to be returned with
appropriate fields initialized.
flags - additional driver specific information. This is sometimes
used to request opening a device with exclusive access.

RESULT

	error - Returns a sign-extended copy of the io_Error field
of the IORequest. Zero if successful, else an error code
is returned.

BUGS

	AmigaDOS file names are not case sensitive, but Exec lists are.  If
the library name is specified in a different case than it exists on
disk, unexpected results may occur.
Prior to V36, tasks could not make OpenDevice calls requiring disk
access (since tasks are not allowed to make dos.library calls).
Now OpenDevice is protected from tasks.

SEE ALSO

CloseDevice(), DoIO(), SendIO(), CheckIO(), AbortIO(), WaitIO()

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