.\" Copyright 2002, Walter Harms <walter.harms@informatik.uni-oldenburg.de>
.\" Copyright 2002, Andries Brouwer <aeb@cwi.nl>
.\" Copyright 2024, Alejandro Colomar <alx@kernel.org>
.\"
.\" SPDX-License-Identifier: GPL-1.0-or-later
.\"
.TH TCSETS 2const 2024-06-15 "Linux man-pages 6.9.1"
.SH NAME
TCGETS,
TCSETS,
TCSETSW,
TCSETSF,
TCGETS2,
TCSETS2,
TCSETSW2,
TCSETSF2,
TCGETA,
TCSETA,
TCSETAW,
TCSETAF
\-
get and set terminal attributes
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.BR "#include <asm/termbits.h>" "  /* Definition of " TC* " constants */"
.B #include <sys/ioctl.h>
.P
.BI "int ioctl(int " fd ", TCGETS, struct termios *" argp );
.BI "int ioctl(int " fd ", TCSETS, const struct termios *" argp );
.BI "int ioctl(int " fd ", TCSETSW, const struct termios *" argp );
.BI "int ioctl(int " fd ", TCSETSF, const struct termios *" argp );
.P
.BI "int ioctl(int " fd ", TCGETS2, struct termios2 *" argp );
.BI "int ioctl(int " fd ", TCSETS2, const struct termios2 *" argp );
.BI "int ioctl(int " fd ", TCSETSW2, const struct termios2 *" argp );
.BI "int ioctl(int " fd ", TCSETSF2, const struct termios2 *" argp );
.P
.BI "int ioctl(int " fd ", TCGETA, struct termio *" argp );
.BI "int ioctl(int " fd ", TCSETA, const struct termio *" argp );
.BI "int ioctl(int " fd ", TCSETAW, const struct termio *" argp );
.BI "int ioctl(int " fd ", TCSETAF, const struct termio *" argp );
.P
.B #include <asm/termbits.h>
.P
.B struct termios;
.B struct termios2;
.B struct termio;
.fi
.SH DESCRIPTION
.TP
.B TCGETS
Equivalent to
.IR "tcgetattr(fd, argp)" .
.IP
Get the current serial port settings.
.TP
.B TCSETS
Equivalent to
.IR "tcsetattr(fd, TCSANOW, argp)" .
.IP
Set the current serial port settings.
.TP
.B TCSETSW
Equivalent to
.IR "tcsetattr(fd, TCSADRAIN, argp)" .
.IP
Allow the output buffer to drain, and
set the current serial port settings.
.TP
.B TCSETSF
Equivalent to
.IR "tcsetattr(fd, TCSAFLUSH, argp)" .
.IP
Allow the output buffer to drain, discard pending input, and
set the current serial port settings.
.P
The following four ioctls
are just like
.BR TCGETS ,
.BR TCSETS ,
.BR TCSETSW ,
.BR TCSETSF ,
except that they take a
.I "struct termios2\~*"
instead of a
.IR "struct termios\~*" .
If the structure member
.B c_cflag
contains the flag
.BR BOTHER ,
then the baud rate is stored in the structure members
.B c_ispeed
and
.B c_ospeed
as integer values.
These ioctls are not supported on all architectures.
.RS
.TP
.B TCGETS2
.TQ
.B TCSETS2
.TQ
.B TCSETSW2
.TQ
.B TCSETSF2
.RE
.P
The following four ioctls are just like
.BR TCGETS ,
.BR TCSETS ,
.BR TCSETSW ,
.BR TCSETSF ,
except that they take a
.I "struct termio\~*"
instead of a
.IR "struct termios\~*" .
.RS
.TP
.B TCGETA
.TQ
.B TCSETA
.TQ
.B TCSETAW
.TQ
.B TCSETAF
.RE
.SH RETURN VALUE
On success,
0 is returned.
On error, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EPERM
Insufficient permission.
.SH HISTORY
.TP
.B TCGETS2
.TQ
.B TCSETS2
.TQ
.B TCSETSW2
.TQ
.B TCSETSF2
.\" linux.git commit 64bb6c5e1ddcd47c951740485026ef08975ee2e6
.\" linux.git commit 592ee3a5e5e2a981ef2829a0380093006d045661
Linux 2.6.20.
.SH CAVEATS
.B struct termios
from
.I <asm/termbits.h>
is different and incompatible with
.B struct termios
from
.IR <termios.h> .
These ioctl calls require
.B struct termios
from
.IR <asm/termbits.h> .
.SH EXAMPLES
Get or set arbitrary baudrate on the serial port.
.P
.\" SRC BEGIN (tcgets.c)
.EX
/* 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\[rs]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] ]\[rs]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 &= \[ti]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 &= \[ti](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\[rs]n", tio.c_ospeed);
    printf("input baud rate: %u\[rs]n", tio.c_ispeed);
\&
    exit(EXIT_SUCCESS);
#endif
}
.EE
.\" SRC END
.SH SEE ALSO
.BR ioctl (2),
.BR ioctl_tty (2),
.BR termios (3)