TIOCMSET(2const)

NAME
TIOCMGET, TIOCMSET, TIOCMBIC, TIOCMBIS, TIOCMIWAIT, TIOCGICOUNT - modem control

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS
#include <asm/termbits.h>  /* Definition of TIOC* constants */
#include <sys/ioctl.h>

int ioctl(int fd, TIOCMGET, int *argp);
int ioctl(int fd, TIOCMSET, const int *argp);
int ioctl(int fd, TIOCMBIC, const int *argp);
int ioctl(int fd, TIOCMBIS, const int *argp);
int ioctl(int fd, TIOCMIWAIT, int arg);
int ioctl(int fd, TIOCGICOUNT, struct serial_icounter_struct *argp);

#include <linux/serial.h>

struct serial_icounter_struct;

DESCRIPTION

TIOCMGET
    Get the status of modem bits.

TIOCMSET
    Set the status of modem bits.

TIOCMBIC
    Clear the indicated modem bits.

TIOCMBIS
    Set the indicated modem bits.

The following bits are used by the above ioctls:

TIOCM_LE | DSR (data set ready/line enable)
TIOCM_DTR | DTR (data terminal ready)
TIOCM_RTS | RTS (request to send)
TIOCM_ST | Secondary TXD (transmit)
TIOCM_SR | Secondary RXD (receive)
TIOCM_CTS | CTS (clear to send)
TIOCM_CAR | DCD (data carrier detect)
TIOCM_CD | see TIOCM_CAR
TIOCM_RNG | RNG (ring)
TIOCM_RI | see TIOCM_RNG
TIOCM_DSR | DSR (data set ready)

TIOCMIWAIT
    Wait for any of the 4 modem bits (DCD, RI, DSR, CTS) to change. The bits of interest are specified as a bit mask in arg, by ORing together any of the bit values, TIOCM_RNG, TIOCM_DSR, TIOCM_CD, and TIOCM_CTS. The caller should use TIOCGICOUNT to see which bit has changed.

TIOCGICOUNT
    Get counts of input serial line interrupts (DCD, RI, DSR, CTS). The counts are written to the serial_icounter_struct structure pointed to by argp.

    Note: both 1->0 and 0->1 transitions are counted, except for RI, where only 0->1 transitions are counted.

RETURN VALUE
On success, 0 is returned. On error, -1 is returned, and errno is set to indicate the error.

EXAMPLES
Check the condition of DTR on the serial port.

    #include <fcntl.h>
    #include <stdio.h>
    #include <sys/ioctl.h>
    #include <unistd.h>

    int
    main(void)
    {
        int fd, serial;

        fd = open("/dev/ttyS0", O_RDONLY);
        ioctl(fd, TIOCMGET, &serial);
        if (serial & TIOCM_DTR)
            puts("TIOCM_DTR is set");
        else
            puts("TIOCM_DTR is not set");
        close(fd);
    }

SEE ALSO
ioctl(2), ioctl_tty(2)