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TCSETATTR(3)             BSD Library Functions Manual             TCSETATTR(3)

NAME
     cfgetispeed, cfgetospeed, cfmakeraw, cfsetispeed, cfsetospeed, cfsetspeed, tcgetattr, tcsetattr --manipulating -manipulating
     manipulating the termios structure

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #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);

DESCRIPTION
     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.

GETTING AND SETTING THE BAUD RATE
     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.

GETTING AND SETTING THE TERMIOS STATE
     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 pro-cesses. processes.
     cesses.  Attempts to perform these operations shall cause the process group to be sent a SIGTTOU sig-nal. signal.
     nal.  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 underly-ing underlying
     ing terminal file, not just the open file description that is 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.  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; how-ever, however,
     ever, 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>.

     TCSANOW    The change occurs immediately.

     TCSADRAIN  The change occurs after all output written to fildes has been transmitted to the terminal.
                This value of optional_actions should be used when changing parameters that affect output.

     TCSAFLUSH  The change occurs after all output written to fildes has been transmitted to the terminal.
                Additionally, any input that has been received but not read is discarded.

     TCSASOFT   If this value is or'ed into the optional_actions 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 ter-minal. terminal.
     minal.

     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.  Other-wise, Otherwise,
     wise, it makes all of the requested changes it can.  If the specified input and output baud rates dif-fer differ
     fer 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]            The fildes argument to tcgetattr() or tcsetattr() was not a valid file descriptor.

     [EINTR]            The tcsetattr() function was interrupted by a signal.

     [EINVAL]           The optional_actions 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]           The file associated with the fildes argument to tcgetattr() or tcsetattr() is not a
                        terminal.

SEE ALSO
     tcsendbreak(3), termios(4)

STANDARDS
     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.

BSD                             January 2, 1994                            BSD

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