This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                   CFGETISPEED(3POSIX)

       The  cfgetispeed()  function  shall  extract  the input baud rate from the termios structure to which the
       termios_p argument points.

       This function shall return exactly the value in the termios data structure, without interpretation.

       No errors are defined.

       Thefollowingsectionsareinformative.

       None.

       None.

       cfgetispeed — get input baud rate

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       The  term ``baud'' is used historically here, but is not technically correct. This is properly ``bits per
       second'', which may not be the same as baud. However, the term is used because of  the  historical  usage
       and understanding.

       The  cfgetospeed(),  cfgetispeed(),  cfsetospeed(),  and cfsetispeed() functions do not take arguments as
       numbers, but rather as symbolic names. There are two reasons for this:

        1. Historically, numbers were not used because of the way the rate was stored  in  the  data  structure.
           This is retained even though a function is now used.

        2. More  importantly,  only  a limited set of possible rates is at all portable, and this constrains the
           application to that set.

       There is nothing to prevent an implementation accepting as an extension a number (such as 126), and since
       the encoding of the Bxxx symbols is not specified, this can be done to avoid introducing ambiguity.

       Setting the input baud rate to zero was a mechanism to allow for split baud rates. Clarifications in this
       volume of POSIX.1‐2017 have made it possible to determine  whether  split  rates  are  supported  and  to
       support  them without having to treat zero as a special case. Since this functionality is also confusing,
       it has been declared obsolescent.  The 0 argument referred to is the literal constant 0, not the symbolic
       constant B0. This volume of POSIX.1‐2017 does not preclude B0 from being defined as the value 0; in fact,
       implementations would likely benefit from the two being equivalent. This volume of POSIX.1‐2017 does  not
       fully  specify  whether  the  previous  cfsetispeed() value is retained after a tcgetattr() as the actual
       value or as zero. Therefore, conforming applications should always set both the input  speed  and  output
       speed when setting either.

       In  historical implementations, the baud rate information is traditionally kept in c_cflag.  Applications
       should be written to presume that this might be the case (and thus not blindly copy c_cflag), but not  to
       rely on it in case it is in some other field of the structure. Setting the c_cflag field absolutely after
       setting  a  baud  rate is a non-portable action because of this. In general, the unused parts of the flag
       fields might be used by the implementation and should not be blindly copied from the descriptions of  one
       terminal device to another.

       Upon successful completion, cfgetispeed() shall return a value of type  speed_t  representing  the  input
       baud rate.

cfgetospeed(), cfsetispeed(), cfsetospeed(), tcgetattr()

       The Base Definitions volume of POSIX.1‐2017, Chapter11, GeneralTerminalInterface, <termios.h>

       #include <termios.h>

       speed_t cfgetispeed(const struct termios *termios_p);