TTY_IOCTL(4) | Linux Programmer's Manual | TTY_IOCTL(4) |
NAME
tty_ioctl - ioctls for terminals and serial linesSYNOPSIS
#include <termios.h>DESCRIPTION
The ioctl(2) call for terminals and serial ports accepts many possible command arguments. Most require a third argument, of varying type, here called argp or arg.Use of ioctl makes for nonportable programs. Use the POSIX interface described in termios(3) whenever possible.
Get and set terminal attributes
- TCGETS struct termios * argp
-
Equivalent to
tcgetattr(fd, argp).
- TCSETS const struct termios * argp
-
Equivalent to
tcsetattr(fd, TCSANOW, argp).
- TCSETSW const struct termios * argp
-
Equivalent to
tcsetattr(fd, TCSADRAIN, argp).
- TCSETSF const struct termios * argp
-
Equivalent to
tcsetattr(fd, TCSAFLUSH, argp).
The following four ioctls are just like TCGETS, TCSETS, TCSETSW, TCSETSF, except that they take a struct termio * instead of a struct termios *.
- TCGETA struct termio * argp
- TCSETA const struct termio * argp
- TCSETAW const struct termio * argp
- TCSETAF const struct termio * argp
Locking the termios structure
The termios structure of a terminal can be locked. The lock is itself a termios structure, with nonzero bits or fields indicating a locked value.- TIOCGLCKTRMIOS struct termios * argp
- Gets the locking status of the termios structure of the terminal.
- TIOCSLCKTRMIOS const struct termios * argp
- Sets the locking status of the termios structure of the terminal. Only root (more precisely: a process with the CAP_SYS_ADMIN capability) can do this.
Get and set window size
Window sizes are kept in the kernel, but not used by the kernel (except in the case of virtual consoles, where the kernel will update the window size when the size of the virtual console changes, for example, by loading a new font).- TIOCGWINSZ struct winsize * argp
- Get window size.
- TIOCSWINSZ const struct winsize * argp
- Set window size.
The struct used by these ioctls is defined as
struct winsize {
unsigned short ws_row;
unsigned short ws_col;
unsigned short ws_xpixel; /* unused */
unsigned short ws_ypixel; /* unused */
};
When the window size changes, a SIGWINCH signal is sent to the foreground process group.
Sending a break
- TCSBRK int arg
-
Equivalent to
tcsendbreak(fd, arg).
- TCSBRKP int arg
- So-called "POSIX version" of TCSBRK. It treats nonzero arg as a timeinterval measured in deciseconds, and does nothing when the driver does not support breaks.
- TIOCSBRK void
- Turn break on, that is, start sending zero bits.
- TIOCCBRK void
- Turn break off, that is, stop sending zero bits.
Software flow control
- TCXONC int arg
-
Equivalent to
tcflow(fd, arg).
Buffer count and flushing
- FIONREAD int * argp
- Get the number of bytes in the input buffer.
- TIOCINQ int * argp
- Same as FIONREAD.
- TIOCOUTQ int * argp
- Get the number of bytes in the output buffer.
- TCFLSH int arg
-
Equivalent to
tcflush(fd, arg).
Faking input
- TIOCSTI const char * argp
- Insert the given byte in the input queue.
Redirecting console output
- TIOCCONS void
- Redirect output that would have gone to /dev/console or /dev/tty0 to the given terminal. If that was a pseudoterminal master, send it to the slave. In Linux before version 2.6.10, anybody can do this as long as the output was not redirected yet; since version 2.6.10, only root (a process with the CAP_SYS_ADMIN capability) may do this. If output was redirected already EBUSY is returned, but redirection can be stopped by using this ioctl with fd pointing at /dev/console or /dev/tty0.
Controlling terminal
- TIOCSCTTY int arg
- Make the given terminal the controlling terminal of the calling process. The calling process must be a session leader and not have a controlling terminal already. If this terminal is already the controlling terminal of a different session group then the ioctl fails with EPERM, unless the caller is root (more precisely: has the CAP_SYS_ADMIN capability) and arg equals 1, in which case the terminal is stolen, and all processes that had it as controlling terminal lose it.
- TIOCNOTTY void
- If the given terminal was the controlling terminal of the calling process, give up this controlling terminal. If the process was session leader, then send SIGHUP and SIGCONT to the foreground process group and all processes in the current session lose their controlling terminal.
Process group and session ID
- TIOCGPGRP pid_t * argp
-
When successful, equivalent to
*argp = tcgetpgrp(fd).
- TIOCSPGRP const pid_t * argp
-
Equivalent to
tcsetpgrp(fd, *argp).
- TIOCGSID pid_t * argp
- Get the session ID of the given terminal. This will fail with ENOTTY in case the terminal is not a master pseudoterminal and not our controlling terminal. Strange.
Exclusive mode
- TIOCEXCL void
- Put the terminal into exclusive mode. No further open(2) operations on the terminal are permitted. (They will fail with EBUSY, except for root, that is, a process with the CAP_SYS_ADMIN capability.)
- TIOCNXCL void
- Disable exclusive mode.
Line discipline
- TIOCGETD int * argp
- Get the line discipline of the terminal.
- TIOCSETD const int * argp
- Set the line discipline of the terminal.
Pseudoterminal ioctls
- TIOCPKT const int * argp
-
Enable (when *
argp is nonzero) or disable packet mode. Can be applied to the master side of a pseudoterminal only (and will return
ENOTTY otherwise). In packet mode, each subsequent
read(2) will return a packet that either contains a single nonzero control byte, or has a single byte containing zero (' ') followed by data written on the slave side of the pseudoterminal. If the first byte is not
TIOCPKT_DATA (0), it is an OR of one or more of the following bits:
TIOCPKT_FLUSHREAD The read queue for the terminal is flushed.
TIOCPKT_FLUSHWRITE The write queue for the terminal is flushed.
TIOCPKT_STOP Output to the terminal is stopped.
TIOCPKT_START Output to the terminal is restarted.
TIOCPKT_DOSTOP The start and stop characters are ^S/ ^Q.
TIOCPKT_NOSTOP The start and stop characters are not ^S/ ^Q.
Modem control
- TIOCMGET int * argp
- get the status of modem bits.
- TIOCMSET const int * argp
- set the status of modem bits.
- TIOCMBIC const int * argp
- clear the indicated modem bits.
- TIOCMBIS const int * argp
- set the indicated modem bits.
Bits used by these four ioctls:
TIOCM_LE DSR (data set ready/line enable)
TIOCM_DTR DTR (data terminal ready)
TIOCM_RTS RTS (request to send)
TIOCM_ST Secondary TXD (transmit)
TIOCM_SR Secondary RXD (receive)
TIOCM_CTS CTS (clear to send)
TIOCM_CAR DCD (data carrier detect)
TIOCM_CD see TIOCM_CAR
TIOCM_RNG RNG (ring)
TIOCM_RI see TIOCM_RNG
TIOCM_DSR DSR (data set ready)
Marking a line as local
- TIOCGSOFTCAR int * argp
- ("Get software carrier flag") Get the status of the CLOCAL flag in the c_cflag field of the termios structure.
- TIOCSSOFTCAR const int * argp
- ("Set software carrier flag") Set the CLOCAL flag in the termios structure when * argp is nonzero, and clear it otherwise.
If the CLOCAL flag for a line is off, the hardware carrier detect (DCD) signal is significant, and an open(2) of the corresponding terminal will block until DCD is asserted, unless the O_NONBLOCK flag is given. If CLOCAL is set, the line behaves as if DCD is always asserted. The software carrier flag is usually turned on for local devices, and is off for lines with modems.
Linux-specific
For the TIOCLINUX ioctl, see console_ioctl(4).Kernel debugging
#include <linux/tty.h>- TIOCTTYGSTRUCT struct tty_struct * argp
- Get the tty_struct corresponding to fd.
RETURN VALUE
The ioctl(2) system call returns 0 on success. On error it returns -1 and sets errno appropriately.ERRORS
- EINVAL
- Invalid command parameter.
- ENOIOCTLCMD
- Unknown command.
- ENOTTY
- Inappropriate fd.
- EPERM
- Insufficient permission.
EXAMPLE
Check the condition of DTR on the serial port.#include <termios.h>
#include <fcntl.h>
#include <sys/ioctl.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 not set");
else
puts("TIOCM_DTR is set");
close(fd);
}
SEE ALSO
ioctl(2), termios(3), console_ioctl(4), pty(7)COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.2008-10-29 | Linux |