DCMD_CHR_LINESTATUS

Synopsis:

#include <sys/dcmd_chr.h>

#define DCMD_CHR_LINESTATUS   __DIOF(_CMD_IOCTL_TTY, 106, int) /* TIOCMGET */

Arguments to devctl():

Argument	Value
`filedes`	A file descriptor that you obtained by opening the device.
`dcmd`	DCMD_CHR_LINESTATUS
`dev_data_ptr`	A pointer to an int
`n_bytes`	`sizeof(int)`
`dev_info_ptr`	NULL

Description:

This command gets line status information for the terminal device and is usually associated with the control lines of a serial port. It's also implemented as the TIOCMGET ioctl() command.

The contents of the returned data depend on the device. The stty utility calls this function and displays this information.

Input:

None.

Output:

The line status information, which is a combination of the following bits (depending on the type of device):

Device type	Bit	Description
Serial	_LINESTATUS_SER_DTR (TIOCM_DTR)	Data terminal ready
	_LINESTATUS_SER_RTS (TIOCM_RTS)	Request to send
	_LINESTATUS_SER_CTS (TIOCM_CTS)	Clear to send
	_LINESTATUS_SER_DSR (TIOCM_DSR)	Data set ready
	_LINESTATUS_SER_RI (TIOCM_RI or TIOCM_RNG)	Ring
	_LINESTATUS_SER_CD (TIOCM_CAR or TIOCM_CD)	Carrier detect
Console	_LINESTATUS_CON_SCROLL	Scroll Lock is on
	_LINESTATUS_CON_NUM	Num Lock is on
	_LINESTATUS_CON_CAPS	Caps Lock is on
	_LINESTATUS_CON_SHIFT	Shift is pressed (not currently used)
	_LINESTATUS_CON_CTRL	Ctrl is pressed (not currently used)
	_LINESTATUS_CON_ALT	Alt is pressed (not currently used)
Parallel	_LINESTATUS_PAR_NOERROR	No error detected
	_LINESTATUS_PAR_SELECTED	Selected
	_LINESTATUS_PAR_PAPEROUT	No paper
	_LINESTATUS_PAR_NOTACK	Not acknowledge
	_LINESTATUS_PAR_NOTBUSY	Not busy

Example:

Check to see if RTS is set:

int data = 0, error;

if (error = devctl (fd, DCMD_CHR_LINESTATUS, &data, sizeof(data), NULL))
{
   fprintf(stderr, "Error getting RTS: %s\n", strerror ( error ));
   exit(EXIT_FAILURE);
}

if (data & _LINESTATUS_SER_RTS)
{
    printf("RTS is set.\n");
}
else
{
    printf("RTS isn't set.\n");
}