sxt(M)

sxt -- pseudo-device driver

Description

sxt is a pseudo-device driver that interposes a discipline between the standard tty line disciplines and a real device driver. The standard disciplines manipulate virtual tty structures (channels) declared by the sxt driver. sxt acts as a discipline manipulating a real tty structure declared by a real device driver. The sxt driver is currently only used by the shl(C) command.

Virtual ttys are named /dev/sxt?? or /dev/sxt/?? (where ?? is a combination of two digits, each in the range 0 ..7 ) and are allocated in groups of up to eight. Filenames end in three digits, where the first two digits represent the group and the last digit represents the virtual tty number of the group. The /dev/sxt form of the name increases the size of /dev, which adversely affects some commands; the /dev/sxt/ form is not understood by most commands. To allocate a group, a program should exclusively open a file with a name of the form /dev/sxt??0 (channel 0) or /dev/sxt/??0 and then execute a SXTIOCLINK ioctl call to initiate the multiplexing.

Only one channel, the controlling channel, can receive input from the keyboard at a time; others attempting to read will be blocked.

ioctl commands

There are two groups of ioctl(S) commands supported by sxt. The first group contains the standard ioctl commands described in termio(M), with the addition of the following:

TIOCEXCL
Set exclusive use mode: no further opens are permitted until the file has been closed.

TIOCNXCL
Reset exclusive use mode: further opens are once again permitted.
The second group are directives to sxt itself. Some of these may only be executed on channel 0.

SXTIOCLINK
Allocate a channel group and multiplex the virtual ttys onto the real tty. The argument is the number of channels to allocate. This command may only be executed on channel 0. Possible errors include:

EINVAL
The argument is out of range.

ENOTTY
The command was not issued from a real tty.

ENXIO
linesw is not configured with sxt.

EBUSY
An SXTIOCLINK command has already been issued for this real tty.

ENOMEM
Where is no system memory available for allocating the virtual tty structures.

EBADF
Channel 0 was not opened before this call.

SXTIOCSWTCH
Set the controlling channel. Possible errors include:

EINVAL
An invalid channel number was given.

EPERM
The command was not executed from channel 0.

SXTIOCWF
Cause a channel to wait until it is the controlling channel. This command will return the error, EINVAL, if an invalid channel number is given.

SXTIOCUBLK
Turn off the loblk control flag in the virtual tty of the indicated channel. The error EINVAL will be returned if an invalid number or channel 0 is given.

SXTIOCSTAT
Get the status (blocked on input or output) of each channel and store in the sxtblock structure referenced by the argument. The error EFAULT will be returned if the structure cannot be written.

SXTIOCTRACE
Enable tracing. Tracing information is written to the console. This command has no effect if tracing is not configured.

SXTIOCNOTRACE
Disable tracing. This command has no effect if tracing is not configured.

Files


/dev/sxt??[0-7]
virtual tty devices

/dev/sxt/??[0-7]

/usr/include/sys/sxt.h
driver specific definitions

See also

ioctl(S), open(S), shl(C), stty(C), termio(M)
© 2005 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 -- 03 June 2005