(libc.info.gz) Local Modes
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17.4.7 Local Modes
------------------
This section describes the flags for the `c_lflag' member of the
`struct termios' structure. These flags generally control higher-level
aspects of input processing than the input modes flags described in
Input Modes, such as echoing, signals, and the choice of
canonical or noncanonical input.
The `c_lflag' member itself is an integer, and you change the flags
and fields using the operators `&', `|', and `^'. Don't try to specify
the entire value for `c_lflag'--instead, change only specific flags and
leave the rest untouched ( Setting Modes).
-- Macro: tcflag_t ICANON
This bit, if set, enables canonical input processing mode.
Otherwise, input is processed in noncanonical mode.
Canonical or Not.
-- Macro: tcflag_t ECHO
If this bit is set, echoing of input characters back to the
terminal is enabled.
-- Macro: tcflag_t ECHOE
If this bit is set, echoing indicates erasure of input with the
ERASE character by erasing the last character in the current line
from the screen. Otherwise, the character erased is re-echoed to
show what has happened (suitable for a printing terminal).
This bit only controls the display behavior; the `ICANON' bit by
itself controls actual recognition of the ERASE character and
erasure of input, without which `ECHOE' is simply irrelevant.
-- Macro: tcflag_t ECHOPRT
This bit is like `ECHOE', enables display of the ERASE character in
a way that is geared to a hardcopy terminal. When you type the
ERASE character, a `\' character is printed followed by the first
character erased. Typing the ERASE character again just prints
the next character erased. Then, the next time you type a normal
character, a `/' character is printed before the character echoes.
This is a BSD extension, and exists only in BSD systems and the
GNU system.
-- Macro: tcflag_t ECHOK
This bit enables special display of the KILL character by moving
to a new line after echoing the KILL character normally. The
behavior of `ECHOKE' (below) is nicer to look at.
If this bit is not set, the KILL character echoes just as it would
if it were not the KILL character. Then it is up to the user to
remember that the KILL character has erased the preceding input;
there is no indication of this on the screen.
This bit only controls the display behavior; the `ICANON' bit by
itself controls actual recognition of the KILL character and
erasure of input, without which `ECHOK' is simply irrelevant.
-- Macro: tcflag_t ECHOKE
This bit is similar to `ECHOK'. It enables special display of the
KILL character by erasing on the screen the entire line that has
been killed. This is a BSD extension, and exists only in BSD
systems and the GNU system.
-- Macro: tcflag_t ECHONL
If this bit is set and the `ICANON' bit is also set, then the
newline (`'\n'') character is echoed even if the `ECHO' bit is not
set.
-- Macro: tcflag_t ECHOCTL
If this bit is set and the `ECHO' bit is also set, echo control
characters with `^' followed by the corresponding text character.
Thus, control-A echoes as `^A'. This is usually the preferred mode
for interactive input, because echoing a control character back to
the terminal could have some undesired effect on the terminal.
This is a BSD extension, and exists only in BSD systems and the
GNU system.
-- Macro: tcflag_t ISIG
This bit controls whether the INTR, QUIT, and SUSP characters are
recognized. The functions associated with these characters are
performed if and only if this bit is set. Being in canonical or
noncanonical input mode has no affect on the interpretation of
these characters.
You should use caution when disabling recognition of these
characters. Programs that cannot be interrupted interactively are
very user-unfriendly. If you clear this bit, your program should
provide some alternate interface that allows the user to
interactively send the signals associated with these characters,
or to escape from the program.
Signal Characters.
-- Macro: tcflag_t IEXTEN
POSIX.1 gives `IEXTEN' implementation-defined meaning, so you
cannot rely on this interpretation on all systems.
On BSD systems and the GNU system, it enables the LNEXT and
DISCARD characters. Other Special.
-- Macro: tcflag_t NOFLSH
Normally, the INTR, QUIT, and SUSP characters cause input and
output queues for the terminal to be cleared. If this bit is set,
the queues are not cleared.
-- Macro: tcflag_t TOSTOP
If this bit is set and the system supports job control, then
`SIGTTOU' signals are generated by background processes that
attempt to write to the terminal. Access to the Terminal.
The following bits are BSD extensions; they exist only in BSD systems
and the GNU system.
-- Macro: tcflag_t ALTWERASE
This bit determines how far the WERASE character should erase. The
WERASE character erases back to the beginning of a word; the
question is, where do words begin?
If this bit is clear, then the beginning of a word is a
nonwhitespace character following a whitespace character. If the
bit is set, then the beginning of a word is an alphanumeric
character or underscore following a character which is none of
those.
Editing Characters, for more information about the WERASE
character.
-- Macro: tcflag_t FLUSHO
This is the bit that toggles when the user types the DISCARD
character. While this bit is set, all output is discarded.
Other Special.
-- Macro: tcflag_t NOKERNINFO
Setting this bit disables handling of the STATUS character.
Other Special.
-- Macro: tcflag_t PENDIN
If this bit is set, it indicates that there is a line of input that
needs to be reprinted. Typing the REPRINT character sets this
bit; the bit remains set until reprinting is finished.
Editing Characters.
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