termio.4

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 4 代码 · 共 729 行 · 第 1/2 页

the corresponding uppercase letter.
This function is often used in conjunction with IUCLCS.
.PP
If ONLCR is set, the NL character is transmitted as the CR-NL
character pair.
If OCRNL is set, the CR character is transmitted as the NL
character.
If ONOCR is set, no CR
character is transmitted when at column 0 (first position).
If ONLRET is set, the NL
character is assumed to do the carriage-return function;
the column pointer is set to 0 and the delays specified
for CR are used.  Otherwise, the NL character is assumed
to do just the line-feed function;
the column pointer remains unchanged.
The column pointer is also set to 0, if the CR
character is actually transmitted.
.PP
The delay bits specify how long
transmission stops to allow for mechanical or other movement
when certain characters are sent to the terminal.
In all cases, a value of 0 indicates no delay.
If OFILL is set,
fill characters is transmitted
for delay instead of a timed delay.
This is useful for high baud rate terminals
that need only a minimal delay.
If OFDEL is set, the fill character is DEL,
otherwise it is NUL.
.PP
If a form-feed or vertical-tab delay is specified,
it lasts for about two seconds.
.PP
A newline delay lasts about 0.10 seconds.
If ONLRET is set, the carriage-return delays are
used instead of the newline delays.
If OFILL is set, two fill characters is transmitted.
.PP
A carriage-return delay type 1 is dependent on the current column
position.  The type 2 delay is about 0.10 seconds;
the type 3 delay is about 0.15 seconds.
If OFILL is set,
delay type 1 transmits two fill characters;
type 2 transmits four fill characters.
.PP
A horizontal-tab delay type 1 is dependent on the current
column position.
The type 2 delay is about 0.10 seconds.
Type 3 specifies that tabs are to be expanded into spaces.
If OFILL is set, two fill characters is transmitted for any delay.
.PP
A backspace delay lasts about 0.05 seconds.
If SM OFILL is set, one fill character will be transmitted.
.PP
The actual delays depend on line speed and system load.
.PP
The initial output control value is all bits clear.
.PP
The
.I c_cflag
field describes the hardware control of the terminal:
.PP
.ta 13n
.nf
CBAUD	Baud rate:
B0	Hang up
B50	50 baud
B75	75 baud
B110	110 baud
B134	134.5 baud
B150	150 baud
B200	200 baud
B300	300 baud
B600	600 baud
B1200	1200 baud
B1800	1800 baud
B2400	2400 baud
B4800	4800 baud
B9600	9600 baud
B19200	19200 baud
B38400	38400 baud
EXTA	External A (Same as B19200)
EXTB	External B (Same as B38400)
.sp
CSIZE	Character size:
CS5	5 bits
CS6	6 bits
CS7	7 bits
CS8	8 bits
CSTOPB	Send two stop bits, otherwise one.
CREAD	Enable receiver.
PARENB	Parity enable.
PARODD	Odd parity, otherwise even.
HUPCL	Hang up on last close.
CLOCAL	Local line, otherwise dial-up.
.fi
.PP
The CBAUD bits specify the baud rate.
The zero baud rate, B0, is used to hang up the connection.
If B0 is specified, the data-terminal-ready signal will not
be asserted.
Normally, this will disconnect the line.
For any particular hardware, impossible speed changes
are ignored.
.PP
The CSIZE
bits specify the character size in bits
for both transmission and reception.
This size does not include the parity bit, if any.
If CSTOPB is set, two stop bits are used;
otherwise, only one stop bit is used.
For example, at 110 baud, two stops bits are required.
.PP
If PARENB is set, parity generation and detection is enabled
and a parity bit is added to each character.
If parity is enabled,
the PARODD flag specifies odd parity, if set.
Otherwise, even parity is used.
.PP
If CREAD is set, the receiver is enabled.
Otherwise, no characters will be received.
.PP
If HUPCL is set, the line will be disconnected
when the last process with the line open closes it or terminates.
That is, the data-terminal-ready signal will not be asserted.
.PP
If CLOCAL is set, the line is assumed to be a local, direct connection
with no modem control.
Otherwise, modem control is assumed.
.PP
The initial hardware control value after open is
B300, CS8, CREAD, HUPCL.
.PP
The
.I c_lflag
field of the argument structure
is used by the line discipline to control terminal functions.
The basic line discipline (0) provides the following:
.PP
.ta 13n
.nf
ISIG	Enable signals.
ICANON	Canonical input (erase and kill processing).
XCASE	Canonical upper/lower presentation.
ECHO	Enable echo.
ECHOE	Echo erase character as BS-SP-BS.
ECHOK	Echo NL after kill character.
ECHONL	Echo NL.
NOFLSH	Disable flush after interrupt or quit.
.DT
.fi
.PP
If ISIG is set,
each input character is checked against the special
control characters INTR, SWTCH, and QUIT.
If an input character matches one of these control characters,
the function associated with that character is performed.
If ISIG is not set,
no checking is done.
Thus, these special input functions
are possible only if ISIG is set.
These functions can be disabled individually by changing
the value of the control character to
an unlikely or impossible value (for example, 0).
.PP
If ICANON is set,
canonical processing is enabled.
This enables the erase and kill edit functions,
and the assembly of input characters into lines delimited by NL,
EOF, and EOL.
If ICANON is not set,
read requests are satisfied directly
from the input queue.
A read is not satisfied until at least MIN
characters have been received, or
the timeout value, TIME, has expired between characters.
This allows fast bursts of input to be read
efficiently, while still allowing single
character input.
The MIN and TIME values are stored in the position for the EOF and EOL
characters, respectively.
The time value represents tenths of seconds.
.PP
If XCASE is set and if ICANON is set,
an upper-case letter is accepted on input by preceding
it with a backslash (\\), and is output preceded by a backslash (\\).
In this mode, the following escape sequences are generated
on output and accepted on input:
.br
.PP
.nf
for	\`	|	~	{	}
use	\e\|\'	\e\|!	\e\|^	\e\|(	\e\|)
.fi
.PP
For example,
.B A
is input as
.BR \ea ,
.B \en
as
.BR \e\en ,
and
.B \eN
as
.BR \e\e\en .
.PP
If ECHO is set, characters are echoed as received.
.PP
When ICANON is set, the following echo functions are possible.
If ECHO and ECHOE are set, the erase character is echoed as ASCII
BS SP BS, which clears the last character from a CRT screen.
If ECHOE is set and ECHO is not set,
the erase character is echoed as ASCII SP BS.
If ECHOK is set, the NL character is echoed after the
kill character to emphasize that the line
is deleted.
Note that an escape character preceding
the erase or kill character removes any special function.
If ECHONL is set, the NL
character is echoed, even if ECHO is not set.
This is useful for terminals
set to local echo (so-called half duplex).
Unless escaped, the EOF character is not echoed.
Because EOT is the default EOF character,
terminals that respond to EOT are prevented from hanging up.
.PP
If NOFLSH is set, the normal flush of the input and output queues
associated with the quit, switch, and interrupt characters
will not be done.
.PP
The initial line-discipline control value is
all bits clear.
.PP
The
.I c_line
field of the argument structure
is used to specify the line discipline.
Support is provided for the basic termio line discipline only.
For this reason, the value of this field is irrelevant and
should be set to zero (0) by convention.
.PP
The primary
.MS ioctl 2
system calls have the form:
.PP
.B ioctl (fildes, command, arg)
.br
.B struct termio *arg;
.PP
The commands using this form are:
.TP 13
TCGETA
Get the parameters associated with the terminal
and store in the
.I termio
structure referenced by
.IR arg .
.TP
TCSETA
Set the parameters associated with the terminal
from the structure referenced by
.IR arg .
The change is immediate.
.TP
TCSETAW
Wait for the output to drain before
setting the new parameters.
This form should be used when changing parameters
that will affect output.
.TP
TCSETAF
Wait for the output to drain,
then flush the input queue and
set the new parameters.
.PP
Additional
.MS ioctl 2
calls have the form:
.PP
.B ioctl (fildes, command, arg)
.br
.B int arg;
.PP
The commands using this form are:
.TP 13
TCSBRK
Wait for the output to drain.
If
.I arg
is 0,
send a break (zero bits for 0.25 seconds).
.TP
TCXONC
Start/stop control.
If
.I arg
is 0, suspend output;
if 1, restart suspended output.
.TP
TCFLSH
If
.I arg
is 0, flush the input queue;
if 1, flush the output queue;
if 2, flush both the input and output queues.
.PP
MIN/TIME Interaction
.PP
MIN represents the minimum number of characters that should be received 
when the read is satisfied (that is, the characters are returned to the
user).
TIME is a timer of 0.10 second granularity used to time-out bursty and
short-term data transmissions.  The four possible values for
MIN and TIME and their interactions follow:

1. 
MIN > 0, TIME > 0.
In this case, TIME
serves as an intercharacter timer activated after the first character is
received and reset upon receipt of each character.
MIN and TIME interact as follows:
.PP
As soon as one character is received the intercharacter timer is started.
.PP
If MIN
characters are received before the intercharacter timer expires, the
read is satisfied.
.PP
If the timer expires before MIN
characters are received, the characters received to that point are
returned to the user.
.PP
A
.MS read 2
operation will sleep until the MIN and TIME 
mechanism are activated by the receipt of the first character; thus,
at least one character must be returned.
.PP
2.
MIN > 0, TIME = 0.
In this case, because TIME = 0, the timer plays no role and only
MIN is significant.  A
.MS read 2
operation is not satisfied until MIN characters are received.
.PP
3.
MIN = 0, TIME > 0.
In this case, because MIN = 0, TIME
no longer serves as an intercharacter timer, but now serves as a read
timer that is activated as soon as the 
.MS read 2
operation is processed. A
.MS read 2 
operation is satisfied as soon as a single character is 
received or the timer expires, in which case, the 
.MS read 2
operation would not return any characters.
.PP
4.
MIN = 0, TIME = 0.
In this case, return is immediate.  If characters are present,
they are returned to the user.