TCSETATTR(3C) Standard C Library Functions TCSETATTR(3C)
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 sets 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 (see
termio(4I))
referenced by
termios_p as follows:
o If
optional_actions is
TCSANOW, the change will occur
immediately.
o If
optional_actions is
TCSADRAIN, the change will occur after
all output written to
fildes is transmitted. This function
should be used when changing parameters that affect output.
o If
optional_actions is
TCSAFLUSH, the change will occur after
all output written to
fildes is transmitted, and all input so
far received but not read will 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 will no
longer be asserted. Normally, this will 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 will be the
same as the output baud rate stored in the
termios structure.
The
tcsetattr() function will 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 will set all the attributes that
implementation supports as requested and leave all the attributes not
supported by the implementation unchanged. If no part of the request can
be honoured, it will 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 is changed. A subsequent call to
tcgetattr(3C) will
return the actual state of the terminal device (reflecting both the
changes made and not made in the previous
tcsetattr() call). The
tcsetattr() function will not change the values in the
termios structure
whether or not it actually accepts them.
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(3C) on
fildes; an application should modify only fields
and flags defined by this document between the call to
tcgetattr(3C) and
tcsetattr(), leaving all other fields and flags unmodified.
No actions defined by this document, other than a call to
tcsetattr() or
a close of the last file descriptor in the system associated with this
terminal device, will cause any of the terminal attributes defined by
this document to change.
Attempts to use
tcsetattr() from a process which is a member of a
background process group on a
fildes associated with its controlling
terminal, will cause the process group to be sent a
SIGTTOU signal. If
the calling process is blocking or ignoring
SIGTTOU signals, the process
is allowed to perform the operation, and no signal is sent.
USAGE
If trying to change baud rates, applications should call
tcsetattr() then
call
tcgetattr(3C) in order to determine what baud rates were actually
selected.
RETURN VALUES
Upon successful completion,
0 is returned. Otherwise,
-1 is returned and
errno is set to indicate the error.
ERRORS
The
tcsetattr() function will fail if:
EBADF The
fildes argument is not a valid file descriptor.
EINTR A signal interrupted
tcsettattr().
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.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+--------------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+--------------------------------+
|Interface Stability | Standard |
+--------------------+--------------------------------+
|MT-Level | MT-Safe, and Async-Signal-Safe |
+--------------------+--------------------------------+
SEE ALSO
cfgetispeed(3C),
tcgetattr(3C),
termio(4I),
attributes(7),
standards(7) August 14, 2002
TCSETATTR(3C)