trusty (3) tcsetattr.3posix.gz

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 .