termios.html

unix 下的C开发手册,还用详细的例程。

whole line at once;
any number
of bytes, even one, may be requested in a
<i><a href="../xsh/read.html">read()</a></i>
without losing information.
<p>
If {MAX_CANON} is defined for this terminal device, it is
a limit on the number of bytes in a line.
The behaviour
of the system when this limit
is exceeded is implementation-dependent.
If {MAX_CANON} is
not defined, there is no such
limit;
see
<i><a href="../xsh/pathconf.html">pathconf()</a></i>.
<p>
Erase and kill processing occur when
either of two special characters, the ERASE and
KILL characters (see
<xref href=specchar><a href="#tag_008_001_009">
Special Characters
</a></xref>),
is received.
This processing affects
data in the input queue that
has not yet been delimited by a newline (NL), EOF or EOL
character.
This un-delimited data makes up
the current line.
The ERASE character
deletes the last character in the
current line, if there is one.
The KILL character deletes
all data in the current line,
if there are any.
The ERASE and KILL characters have no
effect if there is no data
in the current line.
The ERASE and KILL characters themselves
are not placed in the input
queue.
<h4><a name = "tag_008_001_007">&nbsp;</a>Non-canonical Mode Input Processing</h4>
<xref type="3" name="noncanon"></xref>
In non-canonical mode input processing, input
bytes are not assembled into lines, and
erase and kill processing does not
occur.
The values of the MIN and TIME members of
the
<b>c_cc</b>
array are used
to determine how to process the bytes received.
The ISO&nbsp;POSIX-1 standard does not specify whether the setting of O_NONBLOCK takes
precedence over MIN or TIME settings.
Therefore, if O_NONBLOCK is set,
<i><a href="../xsh/read.html">read()</a></i>
may return immediately, regardless of the setting of MIN or TIME.
Also, if no data is available,
<i><a href="../xsh/read.html">read()</a></i>
may either return 0, or return -1 with
<i>errno</i>
set to [EAGAIN].
<p>
MIN represents the minimum number of
bytes that should be received when the
<i><a href="../xsh/read.html">read()</a></i>
function returns successfully.
TIME is a
timer of 0.1 second granularity that is used to
time out bursty and short-term data transmissions.
If MIN is greater than {MAX_INPUT},
the response to the request is
undefined.
The four possible values for MIN
and TIME and their interactions are
described below.
<h5><a name = "tag_008_001_007_001">&nbsp;</a>Case A: MIN &gt; 0, TIME &gt; 0</h5>
In this case TIME serves as
an inter-byte timer and is activated after the first byte is
received.
Since it is an inter-byte
timer, it is reset after a byte is received.
The
interaction between MIN and TIME is as
follows.
As soon as one byte is received, the
inter-byte timer is started.
If MIN bytes are
received before the inter-byte timer expires
(remember that the timer is reset
upon receipt of each byte), the read is satisfied.
If the
timer expires before MIN bytes are
received, the characters received to that point are
returned to the user.
Note that
if TIME expires at least one byte is returned because
the timer would not have been
enabled unless a byte was received.
In this case (MIN &gt; 0,
TIME &gt; 0) the read blocks until
the MIN and TIME mechanisms are activated by the
receipt of the first byte, or
a signal is received.
If the data is in the buffer at the time of the
<i><a href="../xsh/read.html">read()</a></i>,
the result will be as if the data has been received immediately
after the
<i><a href="../xsh/read.html">read()</a></i>.
<h5><a name = "tag_008_001_007_002">&nbsp;</a>Case B: MIN &gt; 0, TIME = 0</h5>
In this case, since the value
of TIME is zero, the timer plays no role and only MIN is
significant.
A pending read is not
satisfied until MIN bytes are received (that is, the pending
read blocks until MIN bytes
are received), or a signal is received.
A program that
uses this case to read record-based
terminal I/O may block indefinitely in the read
operation.
<h5><a name = "tag_008_001_007_003">&nbsp;</a>Case C: MIN = 0, TIME &gt; 0</h5>
In this case, since MIN = 0,
TIME no longer represents an inter-byte timer.
It now serves
as a read timer that is
activated as soon as the
<i><a href="../xsh/read.html">read()</a></i>
function is processed.
A read is
satisfied as soon as a single
byte is received or the read timer expires.
Note that in this
case if the timer expires, no
bytes are returned.
If the timer does not expire, the only
way the read can be satisfied
is if a byte is received.
In this case the read will not block
indefinitely waiting for a byte;
if
no byte is received within TIME*0.1 seconds after the
read is initiated, the
<i><a href="../xsh/read.html">read()</a></i>
returns a value of zero, having read no data.
If the data is in the buffer at the time of the
<i><a href="../xsh/read.html">read()</a></i>,
the timer is started as if the data has been received immediately
after the
<i><a href="../xsh/read.html">read()</a></i>.
<h5><a name = "tag_008_001_007_004">&nbsp;</a>Case D: MIN = 0, TIME = 0</h5>
The minimum of either the number
of bytes requested or the number of bytes currently
available is returned without waiting for more bytes to be input.
If no characters are available,
<i><a href="../xsh/read.html">read()</a></i>
returns a value of zero, having read no data.
<h4><a name = "tag_008_001_008">&nbsp;</a>Writing Data and Output Processing</h4>
<xref type="3" name="writedata"></xref>
When a process writes one or
more bytes to a terminal device file, they are processed
according to the
<b>c_oflag</b>
field (see
<xref href=outmodes><a href="#tag_008_002_003">
Output Modes
</a></xref>).
The implementation may
provide a buffering mechanism;
as such,
when a call to
<i><a href="../xsh/write.html">write()</a></i>
completes, all of the
bytes written have been scheduled for
transmission to the device, but the transmission
will not necessarily have completed.
See
<i><a href="../xsh/write.html">write()</a></i>
for the effects of
O_NONBLOCK on
<i><a href="../xsh/write.html">write()</a></i>.
<h4><a name = "tag_008_001_009">&nbsp;</a>Special Characters</h4>
<xref type="3" name="specchar"></xref>
Certain characters have special functions on
input or output or both.
These functions are
summarised as follows:
<p>
<dl compact>

<dt>INTR<dd>Special character on input, which is recognised if the ISIG flag is
set.
Generates a SIGINT signal which is sent to all processes
in the foreground process group for which the terminal is
the controlling terminal.
If
ISIG is set, the INTR character is discarded when processed.

<dt>QUIT<dd>Special character on input, which is recognised if the ISIG flag is
set.
Generates a SIGQUIT signal which is sent to all processes
in the foreground process group for which the terminal is the
controlling terminal.
If
ISIG is set, the QUIT character is discarded when processed.

<dt>ERASE<dd>Special character on input, which is recognised if the ICANON flag is
set.
Erases the last character in the current line;
see
<xref href=canon><a href="#tag_008_001_006">
Canonical Mode Input Processing
</a></xref>.
It will not erase beyond the
start of a line, as delimited by an NL, EOF or EOL character.
If
ICANON is set, the ERASE character is discarded when processed.

<dt>KILL<dd>Special character on input, which is recognised if the ICANON flag is
set.
Deletes the entire line, as delimited by an NL, EOF or EOL
character.
If ICANON is set, the KILL character is discarded when
processed.

<dt>EOF<dd>Special character on input, which is recognised if the ICANON flag is
set.
When received, all the bytes waiting to be read are
immediately passed to the process without waiting for a newline,
and the EOF is discarded.
Thus, if there are no bytes waiting (that
is, the EOF occurred at the beginning of a line), a byte count of
zero is returned from the
<i><a href="../xsh/read.html">read()</a></i>,
representing an end-of-file
indication.
If ICANON is set, the EOF character is discarded when
processed.

<dt>NL<dd>Special character on input, which is recognised if the ICANON flag is
set.
It is the line delimiter
newline.
It cannot be changed.

<dt>EOL<dd>Special character on input, which
is recognised if the ICANON flag is
set.
It is an additional line delimiter, like NL.

<dt>SUSP<dd>If the
ISIG flag is set, receipt of the SUSP character causes a
SIGTSTP signal to be sent to all processes in the foreground
process group for which the terminal is the
controlling terminal, and the SUSP character
is discarded when processed.

<dt>STOP<dd>Special character on
both input and output, which is recognised if the
IXON (output control) or IXOFF (input control) flag is set.
Can be used to suspend output
temporarily.
It is useful with CRT terminals to
prevent output from disappearing before it can be read.
If IXON is
set, the STOP character is discarded when processed.

<dt>START<dd>Special character on both input and output, which is recognised if the
IXON (output control) or IXOFF (input control) flag is set.
Can be used to resume
output that has been suspended by a STOP character.
If IXON is
set, the START character is discarded when processed.

<dt>CR<dd>Special character on input, which is recognised if the ICANON flag is
set;
it is the
carriage-return character.
When ICANON and ICRNL are set and IGNCR is
not set, this character is translated into an NL, and has the same
effect as an NL character.

</dl>
<p>
The NL and CR characters cannot
be changed.
It is implementation-dependent whether the
START and STOP characters can be
changed.
The values for INTR, QUIT, ERASE, KILL,
EOF, EOL and SUSP
are changeable to suit individual tastes.
Special character functions
associated with changeable special control characters
can be disabled individually.
<p>
If two or more special characters
have the same value, the function performed when that
character is received is undefined.
<p>
A special character is recognised not
only by its value, but also by its context;
for example, an
implementation may support multi-byte sequences that
have a meaning different from the
meaning of the bytes when considered
individually.
Implementations may also support
additional single-byte functions.
These implementation-dependent multi-byte or single-byte
functions are recognised only if the
IEXTEN flag is set;
otherwise, data is received without
interpretation, except as required to recognise the
special characters defined in this section.
<p>
If IEXTEN is set, the
ERASE, KILL and EOF characters can be escaped by a preceding \
character, in which case no special function occurs.
<h4><a name = "tag_008_001_010">&nbsp;</a>Modem Disconnect</h4>
If a modem disconnect is detected
by the terminal interface for a controlling terminal,
and if CLOCAL is not set
in the
<b>c_cflag</b>
field for the terminal (see
<xref href=conmodes><a href="#tag_008_002_004">
Control Modes
</a></xref>),
the SIGHUP signal is sent
to the controlling process for which the terminal is the controlling
terminal.
Unless other arrangements have been
made, this causes the controlling process
to terminate (see
<i><a href="../xsh/exit.html">exit()</a></i>).
Any
subsequent read from the terminal device returns
the value of zero, indicating end-of-file.
(See
<i><a href="../xsh/read.html">read()</a></i>.)
Thus, processes that read a
terminal file and test for end-of-file
can terminate appropriately after a disconnect.
If the EIO condition as specified in
<i><a href="../xsh/read.html">read()</a></i>
also exists, it is unspecified whether on EOF condition or the
[EIO] is returned.
Any subsequent
<i><a href="../xsh/write.html">write()</a></i>
to the terminal device
returns -1, with
<i>errno</i>
set to [EIO], until the
device is closed.
<h4><a name = "tag_008_001_011">&nbsp;</a>Closing a Terminal Device File</h4>
The last process to close a
terminal device file causes any output to be sent to the
device and any input to be
discarded.
If HUPCL is set in the control modes and the
communications port supports a disconnect function,
the terminal device will perform a
disconnect.
<h3><a name = "tag_008_002">&nbsp;</a>Parameters that Can be Set</h3>