TCSETATTR(3C)TCSETATTR(3C)NAMEtcsetattr - 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 termi‐
nal referred to by the open file descriptor fildes (an open file
descriptor associated with a terminal) from the termios structure (see
termio(7I)) referenced by termios_p as follows:
o If optional_actions is TCSANOW, the change will occur imme‐
diately.
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 tcge‐
tattr(3C) will return the actual state of the terminal device (reflect‐
ing 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 tcge‐
tattr(3C) and tcsetattr(), leaving all other fields and flags unmodi‐
fied.
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 back‐
ground process group on a fildes associated with its controlling termi‐
nal, 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(5) for descriptions of the following attributes:
┌────────────────────┬────────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼────────────────────────────────┤
│Interface Stability │ Standard │
├────────────────────┼────────────────────────────────┤
│MT-Level │ MT-Safe, and Async-Signal-Safe │
└────────────────────┴────────────────────────────────┘
SEE ALSOcfgetispeed(3C), tcgetattr(3C), attributes(5), standards(5), termio(7I)
Aug 14, 2002 TCSETATTR(3C)
