Advanced Programming in the UNIX® Environment

ptg10805159

Section 18.2 Overview 677

Function Description

tcgetattr fetch attributes (termiosstructure)

tcsetattr set attributes (termiosstructure)

cfgetispeed get input speed

cfgetospeed get output speed

cfsetispeed set input speed

cfsetospeed set output speed

tcdrain wait for all output to be transmitted

tcflow suspend transmit or receive

tcflush flush pending input and/or output

tcsendbreak send BREAK character

tcgetpgrp get foreground process group ID

tcsetpgrp set foreground process group ID

tcgetsid get process group ID of session leader for controlling TTY

Figure 18.7 Summary of terminal I/O functions

The relationships among the 13 functions shown in Figure18.7 areillustrated in

Figure18.8.

input baud rate output baud rate

struct

termios

terminal line discipline / terminal device driver

cfsetispeedcfgetispeedcfsetospeedcfgetospeed

tcsetattr tcgetattr tcsendbreaktcdraintcflush

tcflow

line control functions

tcgetsidtcgetpgrptcsetpgrp

foreground

process group ID

Figure 18.8Relationships among the terminal-related functions

POSIX.1 doesn’t specify where in thetermiosstructurethe baud rate information is stored;

that is an implementation detail. Some systems, such as Solaris, storethis information in the

c_cflagfield. Linux and BSD-derived systems, such as FreeBSD and Mac OS X, have two

separate fields in the structure: one for the input speed and one for the output speed.