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.

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

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)