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TCSETATTR(3P)              POSIX Programmer's Manual             TCSETATTR(3P)

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
       tcsetattr - set the parameters associated with the terminal
SYNOPSIS
       #include <termios.h>
       int tcsetattr(int fildes, int optional_actions,
              const struct termios *termios_p);

DESCRIPTION
       The tcsetattr() function shall set the parameters associated  with  the
       terminal  referred  to by the open file descriptor fildes (an open file
       descriptor associated with a terminal) from the termios structure  ref-
       erenced by termios_p as follows:
        * If optional_actions is TCSANOW, the change shall occur immediately.
        * If  optional_actions  is TCSADRAIN, the change shall occur after all
          output written to fildes is transmitted.  This  function  should  be
          used when changing parameters that affect output.
        * If  optional_actions  is TCSAFLUSH, the change shall occur after all
          output written to fildes  is  transmitted,  and  all  input  so  far
          received but not read shall be discarded before the change is made.
       If  the  output baud rate stored in the termios structure pointed to by
       termios_p is the zero baud rate, B0, the modem control lines  shall  no
       longer be asserted. Normally, this shall disconnect the line.
       If  the  input  baud rate stored in the termios structure pointed to by
       termios_p is 0, the input baud rate given to the hardware is  the  same
       as the output baud rate stored in the termios structure.
       The  tcsetattr()  function  shall return successfully if it was able to
       perform any of the requested actions, even if  some  of  the  requested
       actions  could  not  be performed. It shall set all the attributes that
       the implementation supports as requested and leave all  the  attributes
       not  supported  by  the  implementation  unchanged.   If no part of the
       request can be honored, it shall return -1 and set errno  to  [EINVAL].
       If the input and output baud rates differ and are a combination that is
       not supported, neither baud rate shall be changed. A subsequent call to
       tcgetattr()  shall  return  the  actual  state  of  the terminal device
       (reflecting both the changes made and not made in  the  previous  tcse-
       tattr()  call).  The  tcsetattr()  function shall not change the values
       found in the termios structure under any circumstances.
       The effect of tcsetattr() is undefined if  the  value  of  the  termios
       structure  pointed to by termios_p was not derived from the result of a
       call to tcgetattr() on fildes; an application should modify only fields
       and  flags  defined  by this volume of IEEE Std 1003.1-2001 between the
       call to tcgetattr() and tcsetattr(), leaving all other fields and flags
       unmodified.
       No actions defined by this volume of IEEE Std 1003.1-2001, other than a
       call to tcsetattr() or a close of the last file descriptor in the  sys-
       tem associated with this terminal device, shall cause any of the termi-
       nal attributes  defined  by  this  volume  of  IEEE Std 1003.1-2001  to
       change.
       If  tcsetattr()  is  called from a process which is a member of a back-
       ground process group on a fildes associated with its controlling termi-
       nal:
        * If  the calling process is blocking or ignoring SIGTTOU signals, the
          operation completes normally and no signal is sent.
        * Otherwise, a SIGTTOU signal shall be sent to the process group.
RETURN VALUE
       Upon successful completion, 0 shall be returned. Otherwise, -1 shall be
       returned and errno set to indicate the error.
ERRORS
       The tcsetattr() function shall fail if:
       EBADF  The fildes argument is not a valid file descriptor.
       EINTR  A signal interrupted tcsetattr().
       EINVAL The  optional_actions  argument  is not a supported value, or an
              attempt was made to  change  an  attribute  represented  in  the
              termios structure to an unsupported value.
       ENOTTY The file associated with fildes is not a terminal.

       The tcsetattr() function may fail if:
       EIO    The  process  group  of the writing process is orphaned, and the
              writing process is not ignoring or blocking SIGTTOU.

       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       If trying to change baud rates, applications  should  call  tcsetattr()
       then  call tcgetattr() in order to determine what baud rates were actu-
       ally selected.
RATIONALE
       The tcsetattr() function can be interrupted  in  the  following  situa-
       tions:
        * It is interrupted while waiting for output to drain.
        * It  is called from a process in a background process group and SIGT-
          TOU is caught.
       See also the RATIONALE section in tcgetattr().
FUTURE DIRECTIONS
       Using an input baud rate of 0 to set the input rate equal to the output
       rate  may not necessarily be supported in a future version of this vol-
       ume of IEEE Std 1003.1-2001.
SEE ALSO
       cfgetispeed(),   tcgetattr(),   the   Base   Definitions   volume    of
       IEEE Std 1003.1-2001,   Chapter   11,   General   Terminal   Interface,
       <termios.h>, <unistd.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 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 .

IEEE/The Open Group                  2003                        TCSETATTR(3P)