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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | HISTORY | CAVEATS | EXAMPLES | SEE ALSO | COLOPHON |
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TCSETS(2const) TCSETS(2const)
TCGETS, TCSETS, TCSETSW, TCSETSF, TCGETS2, TCSETS2, TCSETSW2,
TCSETSF2, TCGETA, TCSETA, TCSETAW, TCSETAF - get and set terminal
attributes
Standard C library (libc, -lc)
#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;
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
On success, 0 is returned. On error, -1 is returned and errno is
set to indicate the error.
EPERM Insufficient permission.
TCGETS2
TCSETS2
TCSETSW2
TCSETSF2
Linux 2.6.20.
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>.
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
}
ioctl(2), ioctl_tty(2), termios(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
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⟨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
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2025-08-11. If you discover any rendering problems in this HTML
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man-pages@man7.org
Linux man-pages 6.15 2025-05-17 TCSETS(2const)
Pages that refer to this page: ioctl_tty(2), TIOCSLCKTRMIOS(2const)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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