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 referenced 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  tcsetattr()  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 system associated with this
       terminal device, shall cause any of the terminal 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 background process group on
       a fildes associated with its controlling terminal:

        * 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 actually selected.

RATIONALE

       The tcsetattr() function can be interrupted in the following situations:

        * It is interrupted while waiting for output to drain.

        * It is called from a process in a background process group and SIGTTOU 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 volume 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 .