sysdeps/unix/bsd/tcsendbrk.c

   1 /* Copyright (C) 1991-2018 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <stddef.h>
  20 #include <signal.h>
  21 #include <termios.h>
  22 #include <unistd.h>
  23 #include "bsdtty.h"
  24 #include <sys/file.h>
  25 #include <sys/time.h>
  26 #include <sys/types.h>
  27
  28 /* Send zero bits on FD.  */
  29 int
  30 tcsendbreak (int fd, int duration)
  31 {
  32   struct timeval delay;
  33
  34   /* The break lasts 0.25 to 0.5 seconds if DURATION is zero,
  35      and an implementation-defined period if DURATION is nonzero.
  36      We define a positive DURATION to be number of microseconds to break.  */
  37   if (duration <= 0)
  38     duration = 400000;
  39
  40   delay.tv_sec = 0;
  41   delay.tv_usec = duration;
  42
  43   /* Starting sending break.  */
  44   if (__ioctl (fd, TIOCSBRK, (void *) NULL) < 0)
  45     return -1;
  46
  47   /* Wait DURATION microseconds.  */
  48   (void) __select (0, (fd_set *) NULL, (fd_set *) NULL, (fd_set *) NULL,
  49                    &delay);
  50
  51   /* Turn off the break.  */
  52   return __ioctl (fd, TIOCCBRK, (void *) NULL);
  53 }