1  /* Send break to terminal.
       2     Copyright (C) 1996-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <errno.h>
      20  #include <stddef.h>
      21  #include <termios.h>
      22  #include <sys/ioctl.h>
      23  
      24  /* Send zero bits on FD.  */
      25  int
      26  tcsendbreak (int fd, int duration)
      27  {
      28    /* The break lasts 0.25 to 0.5 seconds if DURATION is zero,
      29       and an implementation-defined period if DURATION is nonzero.
      30       We define a positive DURATION to be number of milliseconds to break.  */
      31    if (duration <= 0)
      32      return __ioctl (fd, TCSBRK, 0);
      33  
      34  #ifdef TCSBRKP
      35    /* Probably Linux-specific: a positive third TCSBRKP ioctl argument is
      36       defined to be the number of 100ms units to break.  */
      37    return __ioctl (fd, TCSBRKP, (duration + 99) / 100);
      38  #else
      39    /* ioctl can't send a break of any other duration for us.
      40       This could be changed to use trickery (e.g. lower speed and
      41       send a '\0') to send the break, but for now just return an error.  */
      42    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
      43  #endif
      44  }