18.6. stty Command

All the options described in the previous section can be examined and changed from within a program, with the tcgetattr and tcsetattr functions (Section 18.4) or from the command line (or a shell script), with the stty(1) command. This command is simply an interface to the first six functions that we listed in Figure 18.7. If we execute this command with its -a option, it displays all the terminal options:

$ stty -a
speed 9600 baud; 25 rows; 80 columns;
lflags: icanon isig iexten echo echoe -echok echoke -echonl echoctl
        -echoprt -altwerase -noflsh -tostop -flusho pendin -nokerninfo
        -extproc
iflags: -istrip icrnl -inlcr -igncr ixon -ixoff ixany imaxbel -ignbrk
        brkint -inpck -ignpar -parmrk
oflags: opost onlcr -ocrnl -oxtabs -onocr -onlret
cflags: cread cs8 -parenb -parodd hupcl -clocal -cstopb -crtscts
        -dsrflow -dtrflow -mdmbuf
cchars: discard = ^O; dsusp = ^Y; eof = ^D; eol = <undef>;
        eol2 = <undef>; erase = ^H; erase2 = ^?; intr = ^C; kill = ^U;
        lnext = ^V; min = 1; quit = ^; reprint = ^R; start = ^Q;
        status = ^T; stop = ^S; susp = ^Z; time = 0; werase = ^W;

Option names preceded by a hyphen are disabled. The last four lines display the current settings for each of the terminal special characters (Section 18.3). The first line displays the number of rows and columns for the current terminal window; we discuss this in Section 18.12.

The stty command uses its standard input to get and set the terminal option flags. Although some older implementations used standard output, POSIX.1 requires that the standard input be used. All four implementations discussed in this text provide versions of stty that operate on standard input. This means that we can type

          stty -a </dev/tty1a

if we are interested in discovering the settings on the terminal named tty1a.