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tcsetattr(3)             BSD Library Functions Manual             tcsetattr(3)


NAME

     cfgetispeed, cfgetospeed, cfmakeraw, cfsetispeed, cfsetospeed,
     cfsetspeed, tcgetattr, tcsetattr -- 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 rep-
     resented; 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 struc-
     ture 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 processes.  Attempts to
     perform these operations shall cause the process group to be sent a SIGT-
     TOU signal.  If the calling process is blocking or ignoring SIGTTOU sig-
     nals, 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 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 termi-
     nal 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>.

     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 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 com-
     bination 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() func-
                        tion 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

Mac OS X 10.8 - Generated Fri Aug 31 15:59:59 CDT 2012
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