'\" t
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: GPL-1.0-or-later
.\"
.TH TIOCMSET 2const (date) "Linux man-pages (unreleased)"
.SH NAME
TIOCMGET,
TIOCMSET,
TIOCMBIC,
TIOCMBIS,
TIOCMIWAIT,
TIOCGICOUNT
\-
modem control
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.BR "#include <asm/termbits.h>" "  /* Definition of " TIOC* " constants */"
.B #include <sys/ioctl.h>
.P
.BI "int ioctl(int " fd ", TIOCMGET, int *" argp );
.BI "int ioctl(int " fd ", TIOCMSET, const int *" argp );
.BI "int ioctl(int " fd ", TIOCMBIC, const int *" argp );
.BI "int ioctl(int " fd ", TIOCMBIS, const int *" argp );
.BI "int ioctl(int " fd ", TIOCMIWAIT, int " arg );
.BI "int ioctl(int " fd ", TIOCGICOUNT, struct serial_icounter_struct *" argp );
.P
.B #include <linux/serial.h>
.P
.B struct serial_icounter_struct;
.fi
.SH DESCRIPTION
.TP
.B TIOCMGET
Get the status of modem bits.
.TP
.B TIOCMSET
Set the status of modem bits.
.TP
.B TIOCMBIC
Clear the indicated modem bits.
.TP
.B TIOCMBIS
Set the indicated modem bits.
.P
The following bits are used by the above ioctls:
.P
.TS
lb l.
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)
.TE
.TP
.B 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
.IR arg ,
by ORing together any of the bit values,
.BR TIOCM_RNG ,
.BR TIOCM_DSR ,
.BR TIOCM_CD ,
and
.BR TIOCM_CTS .
The caller should use
.B TIOCGICOUNT
to see which bit has changed.
.TP
.B TIOCGICOUNT
Get counts of input serial line interrupts (DCD, RI, DSR, CTS).
The counts are written to the
.I serial_icounter_struct
structure pointed to by
.IR argp .
.IP
Note: both 1->0 and 0->1 transitions are counted, except for
RI, where only 0->1 transitions are counted.
.SH RETURN VALUE
On success,
0 is returned.
On error,
\-1 is returned, and
.I errno
is set to indicate the error.
.SH EXAMPLES
Check the condition of DTR on the serial port.
.P
.\" SRC BEGIN (tiocmget.c)
.EX
#include <asm/termbits.h>
#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);
}
.EE
.\" SRC END
.SH SEE ALSO
.BR ioctl (2),
.BR ioctl_tty (2)