speed_t
cfgetispeed(
const struct termios *t
)
int
cfsetispeed(
struct termios *t
, speed_t speed
)
speed_t
cfgetospeed(
const struct termios *t
)
int
cfsetospeed(
struct termios *t
, speed_t speed
)
int
cfsetspeed(
struct termios *t
, speed_t speed
)
void
cfmakeraw(
struct termios *t
)
int
tcgetattr(
int fd
, struct termios *t
)
int
tcsetattr(
int fd
, int action
, const struct termios *t
)
The cfgetispeed, cfsetispeed, cfgetospeed, cfsetospeed and cfsetspeed functions are provided for getting and setting the baud rate values in the termios structure. The effects of the functions on the terminal as described below do not become effective, nor are all errors detected, until the tcsetattr function is called. Certain values for baud rates set in the termios structure and passed to tcsetattr have special meanings. These are discussed in the portion of the manual page that describes the tcsetattr function.
speed_t
is typdef'd in the include file
<
termios.h
>.
The value of the integer corresponds directly to the baud rate being
represented, however, the following symbolic values are defined.
#define B0 0
#define B50 50
#define B75 75
#define B110 110
#define B134 134
#define B150 150
#define B200 200
#define B300 300
#define B600 600
#define B1200 1200
#define B1800 1800
#define B2400 2400
#define B4800 4800
#define B9600 9600
#define B19200 19200
#define B38400 38400
#ifndef _POSIX_SOURCE
#define EXTA 19200
#define EXTB 38400
#endif /*_POSIX_SOURCE */
The
cfgetispeed
function returns the input baud rate in the termios structure referenced by
tp
.
The
cfsetispeed
function sets the input baud rate in the termios structure referenced by
tp
to
speed
.
The
cfgetospeed
function returns the output baud rate in the termios structure referenced by
tp
.
The
cfsetospeed
function sets the output baud rate in the termios structure referenced by
tp
to
speed
.
The
cfsetspeed
function sets both the input and output baud rate in the termios structure
referenced by
tp
to
speed
.
Upon successful completion, the functions cfsetispeed, cfsetospeed, and cfsetspeed return a value of 0. Otherwise, a value of -1 is returned and the global variable errno is set to indicate the error.
In all the functions, although
fd
is an open file descriptor, the functions affect the underlying terminal
file, not just the open file description associated with the particular
file descriptor.
The cfmakeraw function sets the flags stored in the termios structure (initialized by tcgetattr) to a state disabling all input and output processing, giving a ``raw I/O path''. It should be noted that there is no function to reverse this effect. This is because there are a variety of processing options that could be re-enabled and the correct method is for an application to snapshot the current terminal state using the function tcgetattr, setting raw mode with cfmakeraw and the subsequent tcsetattr, and then using another tcsetattr with the saved state to revert to the previous terminal state.
The
tcgetattr
function copies the parameters associated with the terminal referenced
by
fd
to the termios structure referenced by
tp
.
This function is allowed from a background process, however, the terminal
attributes may be subsequently changed by a foreground process.
The
tcsetattr
function sets the parameters associated with the terminal from the
termios structure referenced by
tp
.
The
action
field is created by
or'ing
the following values, as specified in the include file
<termios.h
>.
TCSANOW
TCSADRAIN
fd
has been transmitted to the terminal.
This value of
action
should be used when changing parameters that affect output.
TCSAFLUSH
fd
has been transmitted to the terminal.
Additionally, any input that has been received but not read is discarded.
TCSASOFT
action
value, the values of the
c_cflag,
c_ispeed,
and
c_ospeed
fields are ignored.
The 0 baud rate is used to terminate the connection. If 0 is specified as the output speed to the function tcsetattr, modem control will no longer be asserted on the terminal, disconnecting the terminal.
If zero is specified as the input speed to the function tcsetattr, the input baud rate will be set to the same value as that specified by the output baud rate.
Upon successful completion, the functions tcgetattr and tcsetattr return a value of 0. Otherwise, they return -1 and the global variable errno is set to indicate the error, as follows:
EBADF
]
fd
argument to
tcgetattr
or
tcsetattr
was not a valid file descriptor.
EINTR
]
EINVAL
]
action
argument to the
tcsetattr
function was not valid, or an attempt was made to change an attribute
represented in the termios structure to an unsupported value.
ENOTTY
]
fd
argument to
tcgetattr
or
tcsetattr
is not a terminal.
TCSASOFT
option to the
tcsetattr
function are extensions to the
IEEE Std 1003.1-1988 (``POSIX.1'')
specification.