TCSETS(2const)                                                  TCSETS(2const)

NAME
       TCGETS, TCSETS, TCSETSW, TCSETSF, TCGETS2, TCSETS2, TCSETSW2, TCSETSF2,
       TCGETA, TCSETA, TCSETAW, TCSETAF - get and set terminal attributes

LIBRARY
       Standard C library (libc, -lc)

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

       int ioctl(int fd, TCGETS, struct termios *argp);
       int ioctl(int fd, TCSETS, const struct termios *argp);
       int ioctl(int fd, TCSETSW, const struct termios *argp);
       int ioctl(int fd, TCSETSF, const struct termios *argp);

       int ioctl(int fd, TCGETS2, struct termios2 *argp);
       int ioctl(int fd, TCSETS2, const struct termios2 *argp);
       int ioctl(int fd, TCSETSW2, const struct termios2 *argp);
       int ioctl(int fd, TCSETSF2, const struct termios2 *argp);

       int ioctl(int fd, TCGETA, struct termio *argp);
       int ioctl(int fd, TCSETA, const struct termio *argp);
       int ioctl(int fd, TCSETAW, const struct termio *argp);
       int ioctl(int fd, TCSETAF, const struct termio *argp);

       #include <asm/termbits.h>

       struct termios;
       struct termios2;
       struct termio;

DESCRIPTION
       TCGETS Equivalent to tcgetattr(fd, argp).

              Get the current serial port settings.

       TCSETS Equivalent to tcsetattr(fd, TCSANOW, argp).

              Set the current serial port settings.

       TCSETSW
              Equivalent to tcsetattr(fd, TCSADRAIN, argp).

              Allow the output buffer to drain, and set the current serial
              port settings.

       TCSETSF
              Equivalent to tcsetattr(fd, TCSAFLUSH, argp).

              Allow the output buffer to drain, discard pending input, and set
              the current serial port settings.

       The following four ioctls are just like TCGETS, TCSETS, TCSETSW,
       TCSETSF, except that they take a struct termios2 * instead of a struct
       termios *.  If the structure member c_cflag contains the flag BOTHER,
       then the baud rate is stored in the structure members c_ispeed and
       c_ospeed as integer values.  These ioctls are not supported on all
       architectures.

              TCGETS2
              TCSETS2
              TCSETSW2
              TCSETSF2

       The following four ioctls are just like TCGETS, TCSETS, TCSETSW,
       TCSETSF, except that they take a struct termio * instead of a struct
       termios *.

              TCGETA
              TCSETA
              TCSETAW
              TCSETAF

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

ERRORS
       EPERM  Insufficient permission.

HISTORY
       TCGETS2
       TCSETS2
       TCSETSW2
       TCSETSF2
              Linux 2.6.20.

CAVEATS
       struct termios from <asm/termbits.h> is different and incompatible with
       struct termios from <termios.h>.  These ioctl calls require struct
       termios from <asm/termbits.h>.

EXAMPLES
       Get or set arbitrary baudrate on the serial port.

       /* SPDX-License-Identifier: GPL-2.0-or-later */

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

       int
       main(int argc, char *argv[])
       {
       #if !defined BOTHER
           fprintf(stderr, "BOTHER is unsupported\n");
           /* Program may fallback to TCGETS/TCSETS with Bnnn constants */
           exit(EXIT_FAILURE);
       #else
           /* Declare tio structure, its type depends on supported ioctl */
       # if defined TCGETS2
           struct termios2 tio;
       # else
           struct termios tio;
       # endif
           int fd, rc;

           if (argc != 2 && argc != 3 && argc != 4) {
               fprintf(stderr, "Usage: %s device [output [input] ]\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           fd = open(argv[1], O_RDWR | O_NONBLOCK | O_NOCTTY);
           if (fd < 0) {
               perror("open");
               exit(EXIT_FAILURE);
           }

           /* Get the current serial port settings via supported ioctl */
       # if defined TCGETS2
           rc = ioctl(fd, TCGETS2, &tio);
       # else
           rc = ioctl(fd, TCGETS, &tio);
       # endif
           if (rc) {
               perror("TCGETS");
               close(fd);
               exit(EXIT_FAILURE);
           }

           /* Change baud rate when more arguments were provided */
           if (argc == 3 || argc == 4) {
               /* Clear the current output baud rate and fill a new value */
               tio.c_cflag &= ~CBAUD;
               tio.c_cflag |= BOTHER;
               tio.c_ospeed = atoi(argv[2]);

               /* Clear the current input baud rate and fill a new value */
               tio.c_cflag &= ~(CBAUD << IBSHIFT);
               tio.c_cflag |= BOTHER << IBSHIFT;
               /* When 4th argument is not provided reuse output baud rate */
               tio.c_ispeed = (argc == 4) ? atoi(argv[3]) : atoi(argv[2]);

               /* Set new serial port settings via supported ioctl */
       # if defined TCSETS2
               rc = ioctl(fd, TCSETS2, &tio);
       # else
               rc = ioctl(fd, TCSETS, &tio);
       # endif
               if (rc) {
                   perror("TCSETS");
                   close(fd);
                   exit(EXIT_FAILURE);
               }

               /* And get new values which were really configured */
       # if defined TCGETS2
               rc = ioctl(fd, TCGETS2, &tio);
       # else
               rc = ioctl(fd, TCGETS, &tio);
       # endif
               if (rc) {
                   perror("TCGETS");
                   close(fd);
                   exit(EXIT_FAILURE);
               }
           }

           close(fd);

           printf("output baud rate: %u\n", tio.c_ospeed);
           printf("input baud rate: %u\n", tio.c_ispeed);

           exit(EXIT_SUCCESS);
       #endif
       }

SEE ALSO
       ioctl(2), ioctl_tty(2), termios(3)

Linux man-pages 6.9.1             2024-06-15                    TCSETS(2const)