NAME | SYNOPSIS | FEATURES | DESCRIPTION | GETTING AND SETTING THE BAUD RATE | GETTING AND SETTING THE TERMIOS STATE | STANDARDS | RESTRICTIONS | ATTRIBUTES
#include <termios.h>speed_t cfgetispeed(struct termios * t);
VTTY
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. 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.
The input and output baud rates are found in the termios structure. The unsigned integer
speed_t
is
typdef
ed 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 t .
The cfsetispeed() function sets the input baud rate in the termios structure referenced by t to speed . The cfgetospeed() function returns the output baud rate in the termios structure referenced by t . The cfsetospeed() function sets the output baud rate in the termios structure referenced by t to speed .
The cfsetspeed() function sets both the input and output baud rate in the termios structure referenced by t 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 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 the
SIGTTOU
signal is not sent. See RESTRICTIONS below.
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 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 tcgetattr() function, setting raw mode using 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 in the termios structure referenced by t . This function is allowed from a background process (see RESTRICTIONS); however, the terminal attributes may subsequently be 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> .
The change occurs immediately.
The change occurs after all output written to fd has been transmitted to the terminal. This value of action should be used when changing parameters that affect output.
The change occurs after all output written to has been transmitted to the terminal. Additionally, any input that has been received but not read is discarded.
If this value is or'ed into the 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 0 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 one of the following error conditions:
The fd argument to tcgetattr() or tcsetattr() was not a valid file descriptor.
The tcsetattr() function was interrupted by a signal. See RESTRICTIONS below.
The 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.
The file associated with the fd argument to tcgetattr() or tcsetattr() is not a terminal.
The cfgetispeed() , cfsetispeed() , cfgetospeed() , cfsetospeed() , tcgetattr() and tcsetattr() functions are expected to be compliant with the POSIX 1003.1-88 specification. The cfmakeraw() and cfsetspeed() functions, as well as the TCSASOFT option to the tcsetattr() function are extensions to the POSIX 1003.1-88 specification.
Signals and signals management are not supported.
These library functions (in libbsd.a ) do not support multithreaded applications.
The background semantic is not supported.
See attributes(5) for descriptions of the following attributes:
ATTRIBUTE TYPE | ATTRIBUTE VALUE |
---|---|
Interface Stability | Evolving |
NAME | SYNOPSIS | FEATURES | DESCRIPTION | GETTING AND SETTING THE BAUD RATE | GETTING AND SETTING THE TERMIOS STATE | STANDARDS | RESTRICTIONS | ATTRIBUTES