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TIOCMSET(2const) — Linux manual page

TIOCMSET(2const)TIOCMSET(2const)

NAME        top

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

LIBRARY        top

       Standard C library (libc,-lc)

SYNOPSIS        top

#include <asm/termbits.h>/* Definition ofTIOC*constants */#include <sys/ioctl.h>int ioctl(intfd, TIOCMGET, int *argp);int ioctl(intfd, TIOCMSET, const int *argp);int ioctl(intfd, TIOCMBIC, const int *argp);int ioctl(intfd, TIOCMBIS, const int *argp);int ioctl(intfd, TIOCMIWAIT, intarg);int ioctl(intfd, TIOCGICOUNT, struct serial_icounter_struct *argp);#include <linux/serial.h>struct serial_icounter_struct;

DESCRIPTION        top

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_LEDSR (data set ready/line enable)TIOCM_DTRDTR (data terminal ready)TIOCM_RTSRTS (request to send)TIOCM_STSecondary TXD (transmit)TIOCM_SRSecondary RXD (receive)TIOCM_CTSCTS (clear to send)TIOCM_CARDCD (data carrier detect)TIOCM_CDsee TIOCM_CARTIOCM_RNGRNG (ring)TIOCM_RIsee TIOCM_RNGTIOCM_DSRDSR (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              inarg, by ORing together any of the bit values,TIOCM_RNG,TIOCM_DSR,TIOCM_CD, andTIOCM_CTS.  The caller should useTIOCGICOUNTto see which bit has changed.TIOCGICOUNT              Get counts of input serial line interrupts (DCD, RI, DSR,              CTS).  The counts are written to theserial_icounter_struct              structure pointed to byargp.              Note: both 1->0 and 0->1 transitions are counted, except              for RI, where only 0->1 transitions are counted.

RETURN VALUE        top

       On success, 0 is returned.  On error, -1 is returned, anderrno is       set to indicate the error.

EXAMPLES        top

       Check the condition of DTR on the serial port.       #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);       }

SEE ALSO        top

ioctl(2),ioctl_tty(2)

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17TIOCMSET(2const)

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