TCSETATTR(3) | Library Functions Manual | TCSETATTR(3) |
cfgetispeed
,
cfgetospeed
, cfmakeraw
,
cfsetispeed
, cfsetospeed
,
cfsetspeed
, tcgetattr
,
tcsetattr
— manipulating the
termios structure
Standard C Library (libc, -lc)
#include
<termios.h>
speed_t
cfgetispeed
(const struct termios
*termios_p);
speed_t
cfgetospeed
(const struct termios
*termios_p);
void
cfmakeraw
(struct termios
*termios_p);
int
cfsetispeed
(struct termios
*termios_p, speed_t speed);
int
cfsetospeed
(struct termios
*termios_p, speed_t speed);
int
cfsetspeed
(struct termios
*termios_p, speed_t speed);
int
tcgetattr
(int fildes,
struct termios *termios_p);
int
tcsetattr
(int fildes,
int optional_actions, const struct
termios *termios_p);
The
cfmakeraw
(),
tcgetattr
(), and tcsetattr
()
functions are provided for getting and setting the termios structure.
The
cfgetispeed
(),
cfsetispeed
(),
cfgetospeed
(),
cfsetospeed
(), and
cfsetspeed
() functions are provided for getting and
setting the baud rate values in the termios structure. As described below,
the effects of the functions on the terminal 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.
The input and output baud rates are found in the termios
structure. The unsigned integer speed_t
is typedef'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_C_SOURCE #define EXTA 19200 #define EXTB 38400 #endif /*_POSIX_C_SOURCE */
The
cfgetispeed
()
function returns the input baud rate in the termios structure referenced by
termios_p.
The
cfsetispeed
()
function sets the input baud rate in the termios structure referenced by
termios_p to speed.
The
cfgetospeed
()
function returns the output baud rate in the termios structure referenced by
termios_p.
The
cfsetospeed
()
function sets the output baud rate in the termios structure referenced by
termios_p to speed.
The
cfsetspeed
()
function sets both the input and output baud rate in the termios structure
referenced by termios_p 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.
This section describes the functions that are used to control the general terminal interface. Unless otherwise noted for a specific command, these functions are restricted from use by background processes. Attempts to perform these operations shall 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 the SIGTTOU signal is not sent.
In all of the functions, although fildes is an open file descriptor, the functions affect the underlying terminal file, not just the open file description that is associated with the particular file descriptor.
The
cfmakeraw
()
function modifies the flags stored in the termios structure 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. Because a variety of processing options could be re-enabled, 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
fildes in the termios structure referenced by
termios_p. 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 termios_p. The
optional_actions field is created by
or'ing the following values, as specified in the include
file ⟨termios.h⟩.
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.
If
tcsetattr
()
is unable to make any of the requested changes, it returns -1 and sets
errno. Otherwise, it makes all of the requested changes it can. If the
specified input and output baud rates differ and are a combination that is
not supported, neither baud rate is changed.
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
]tcgetattr
() or tcsetattr
()
was not a valid file descriptor.EINTR
]tcsetattr
() function was interrupted by a
signal.EINVAL
]tcsetattr
() function was not valid, or an attempt
was made to change an attribute represented in the termios structure to an
unsupported value.ENOTTY
]tcgetattr
() or tcsetattr
()
is not a terminal.The cfgetispeed
(),
cfsetispeed
(),
cfgetospeed
(),
cfsetospeed
(), tcgetattr
(),
and tcsetattr
() functions are expected to be
compliant with the IEEE Std 1003.1-1988
(“POSIX.1”) specification. The
cfmakeraw
() and cfsetspeed
()
functions, as well as the TCSASOFT
option to the
tcsetattr
() function are extensions to the
IEEE Std 1003.1-1988 (“POSIX.1”)
specification.
January 2, 1994 | macOS 14.6 |