PROLOG

       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.

NAME

       tcgetattr — get the parameters associated with the terminal

SYNOPSIS

       #include <termios.h>

       int tcgetattr(int fildes, struct termios *termios_p);

DESCRIPTION

       The tcgetattr() function shall get the parameters associated with the terminal referred to
       by fildes and store them in the termios structure referenced  by  termios_p.   The  fildes
       argument is an open file descriptor associated with a terminal.

       The termios_p argument is a pointer to a termios structure.

       The tcgetattr() operation is allowed from any process.

       If  the  terminal  device  supports  different input and output baud rates, the baud rates
       stored in the termios structure returned by tcgetattr()  shall  reflect  the  actual  baud
       rates,  even  if  they  are  equal.  If  differing  baud rates are not supported, the rate
       returned as the output baud rate shall be the actual baud rate.  If  the  terminal  device
       does  not  support  split  baud rates, the input baud rate stored in the termios structure
       shall be the output rate (as one of the symbolic values).

RETURN VALUE

       Upon successful completion, 0 shall be returned. Otherwise, −1 shall be returned and errno
       set to indicate the error.

ERRORS

       The tcgetattr() function shall fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       ENOTTY The file associated with fildes is not a terminal.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       Care  must be taken when changing the terminal attributes. Applications should always do a
       tcgetattr(), save the termios structure  values  returned,  and  then  do  a  tcsetattr(),
       changing  only  the necessary fields. The application should use the values saved from the
       tcgetattr() to reset the terminal state whenever it is done with the  terminal.   This  is
       necessary  because  terminal  attributes  apply  to  the  underlying  port and not to each
       individual open instance; that is, all processes that  have  used  the  terminal  see  the
       latest attribute changes.

       A  program that uses these functions should be written to catch all signals and take other
       appropriate actions to ensure that when the program terminates, whether  planned  or  not,
       the terminal device's state is restored to its original state.

       Existing practice dealing with error returns when only part of a request can be honored is
       based on calls to the ioctl() function. In historical BSD and  System  V  implementations,
       the corresponding ioctl() returns zero if the requested actions were semantically correct,
       even if some of the requested changes could not be made. Many existing applications assume
       this  behavior  and  would  no longer work correctly if the return value were changed from
       zero to −1 in this case.

       Note that either specification has a problem. When zero is returned, it implies everything
       succeeded  even  if  some  of  the  changes were not made. When −1 is returned, it implies
       everything failed even though some of the changes were made.

       Applications that need all of the requested changes made to work  properly  should  follow
       tcsetattr() with a call to tcgetattr() and compare the appropriate field values.

FUTURE DIRECTIONS

       None.

SEE ALSO

       tcsetattr()

       The  Base  Definitions  volume  of  POSIX.1‐2008,  Chapter 11, General Terminal Interface,
       <termios.h>

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1,  2013  Edition,  Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013  by  the
       Institute  of  Electrical  and  Electronics  Engineers,  Inc and The Open Group.  (This is
       POSIX.1-2008 with the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/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 .