xbd_chap11.html

IEEE 1003.1-2003, Single Unix Specification v3

<p class="tent">300 baud</p>
</td>
<td align="left">
<p class="tent">B38400</p>
</td>
<td align="left">
<p class="tent">38400 baud</p>
</td>
</tr>
</table>
</center>

<p>The following functions are provided for getting and setting the values of the input and output baud rates in the <b>termios</b>
structure: <a href="../functions/cfgetispeed.html"><i>cfgetispeed</i>()</a>, <a href=
"../functions/cfgetospeed.html"><i>cfgetospeed</i>()</a>, <a href="../functions/cfsetispeed.html"><i>cfsetispeed</i>()</a>, and <a
href="../functions/cfsetospeed.html"><i>cfsetospeed</i>()</a>. The effects on the terminal device shall not become effective and
not all errors need be detected until the <a href="../functions/tcsetattr.html"><i>tcsetattr</i>()</a> function is successfully
called.</p>

<p>The CSIZE bits shall specify the number of transmitted or received bits per byte. If ISTRIP is not set, the value of all the
other bits is unspecified. If ISTRIP is set, the value of all but the 7 low-order bits shall be zero, but the value of any other
bits beyond CSIZE is unspecified when read. CSIZE shall not include the parity bit, if any. If CSTOPB is set, two stop bits shall
be used; otherwise, one stop bit. For example, at 110 baud, two stop bits are normally used.</p>

<p>If CREAD is set, the receiver shall be enabled; otherwise, no characters shall be received.</p>

<p>If PARENB is set, parity generation and detection shall be enabled and a parity bit is added to each byte. If parity is enabled,
PARODD shall specify odd parity if set; otherwise, even parity shall be used.</p>

<p>If HUPCL is set, the modem control lines for the port shall be lowered when the last process with the port open closes the port
or the process terminates. The modem connection shall be broken.</p>

<p>If CLOCAL is set, a connection shall not depend on the state of the modem status lines. If CLOCAL is clear, the modem status
lines shall be monitored.</p>

<p>Under normal circumstances, a call to the <a href="../functions/open.html"><i>open</i>()</a> function shall wait for the modem
connection to complete. However, if the O_NONBLOCK flag is set (see <a href="../functions/open.html"><i>open</i>()</a>) or if
CLOCAL has been set, the <a href="../functions/open.html"><i>open</i>()</a> function shall return immediately without waiting for
the connection.</p>

<p>If the object for which the control modes are set is not an asynchronous serial connection, some of the modes may be ignored;
for example, if an attempt is made to set the baud rate on a network connection to a terminal on another host, the baud rate need
not be set on the connection between that terminal and the machine to which it is directly connected.</p>

<p>The initial hardware control value after <a href="../functions/open.html"><i>open</i>()</a> is implementation-defined.</p>

<h4><a name="tag_11_02_05"></a>Local Modes</h4>

<p>The <i>c_lflag</i> field of the argument structure is used to control various functions. It is composed of the bitwise-inclusive
OR of the masks shown, which shall be bitwise-distinct. The mask name symbols in this table are defined in <a href=
"termios.h.html"><i>&lt;termios.h&gt;</i></a> ; not all values specified are required to be supported by the underlying
hardware:</p>

<center>
<table border="1" cellpadding="3" align="center">
<tr valign="top">
<th align="center">
<p class="tent"><b>Mask Name</b></p>
</th>
<th align="center">
<p class="tent"><b>Description</b></p>
</th>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">ECHO</p>
</td>
<td align="left">
<p class="tent">Enable echo.</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">ECHOE</p>
</td>
<td align="left">
<p class="tent">Echo ERASE as an error correcting backspace.</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">ECHOK</p>
</td>
<td align="left">
<p class="tent">Echo KILL.</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">ECHONL</p>
</td>
<td align="left">
<p class="tent">Echo &lt;newline&gt;.</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">ICANON</p>
</td>
<td align="left">
<p class="tent">Canonical input (erase and kill processing).</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">IEXTEN</p>
</td>
<td align="left">
<p class="tent">Enable extended (implementation-defined) functions.</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">ISIG</p>
</td>
<td align="left">
<p class="tent">Enable signals.</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">NOFLSH</p>
</td>
<td align="left">
<p class="tent">Disable flush after interrupt, quit, or suspend.</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">TOSTOP</p>
</td>
<td align="left">
<p class="tent">Send SIGTTOU for background output.</p>
</td>
</tr>
</table>
</center>

<p>If ECHO is set, input characters shall be echoed back to the terminal. If ECHO is clear, input characters shall not be
echoed.</p>

<p>If ECHOE and ICANON are set, the ERASE character shall cause the terminal to erase, if possible, the last character in the
current line from the display. If there is no character to erase, an implementation may echo an indication that this was the case,
or do nothing.</p>

<p>If ECHOK and ICANON are set, the KILL character shall either cause the terminal to erase the line from the display or shall echo
the newline character after the KILL character.</p>

<p>If ECHONL and ICANON are set, the newline character shall be echoed even if ECHO is not set.</p>

<p>If ICANON is set, canonical processing shall be enabled. This enables the erase and kill edit functions, and the assembly of
input characters into lines delimited by NL, EOF, and EOL, as described in <a href="#tag_11_01_06">Canonical Mode Input
Processing</a> .</p>

<p>If ICANON is not set, read requests shall be satisfied directly from the input queue. A read shall not be satisfied until at
least MIN bytes have been received or the timeout value TIME expired between bytes. The time value represents tenths of a second.
See <a href="#tag_11_01_07">Non-Canonical Mode Input Processing</a> for more details.</p>

<p>If IEXTEN is set, implementation-defined functions shall be recognized from the input data. It is implementation-defined how
IEXTEN being set interacts with ICANON, ISIG, IXON, or IXOFF. If IEXTEN is not set, implementation-defined functions shall not be
recognized and the corresponding input characters are processed as described for ICANON, ISIG, IXON, and IXOFF.</p>

<p>If ISIG is set, each input character shall be checked against the special control characters INTR, QUIT, and SUSP. If an input
character matches one of these control characters, the function associated with that character shall be performed. If ISIG is not
set, no checking shall be done. Thus these special input functions are possible only if ISIG is set.</p>

<p>If NOFLSH is set, the normal flush of the input and output queues associated with the INTR, QUIT, and SUSP characters shall not
be done.</p>

<p>If TOSTOP is set, the signal SIGTTOU shall be sent to the process group of a process that tries to write to its controlling
terminal if it is not in the foreground process group for that terminal. This signal, by default, stops the members of the process
group. Otherwise, the output generated by that process shall be output to the current output stream. Processes that are blocking or
ignoring SIGTTOU signals are excepted and allowed to produce output, and the SIGTTOU signal shall not be sent.</p>

<p>The initial local control value after <a href="../functions/open.html"><i>open</i>()</a> is implementation-defined.</p>

<h4><a name="tag_11_02_06"></a>Special Control Characters</h4>

<p>The special control character values shall be defined by the array <i>c_cc</i>. The subscript name and description for each
element in both canonical and non-canonical modes are as follows:</p>

<center>
<table border="1" cellpadding="3" align="center">
<tr valign="top">
<th colspan="2" align="center">
<p class="tent"><b>Subscript Usage</b></p>
</th>
<th align="center">
<p class="tent"><b>&nbsp;</b></p>
</th>
</tr>

<tr valign="top">
<th align="center">
<p class="tent"><b>_</b></p>
</th>
<th align="center">
<p class="tent"><b>_</b></p>
</th>
<th align="center">
<p class="tent"><b>&nbsp;</b></p>
</th>
</tr>

<tr valign="top">
<th align="center">
<p class="tent"><b>Canonical</b></p>
</th>
<th align="center">
<p class="tent"><b>Non-Canonical</b></p>
</th>
<th align="center">
<p class="tent"><b>&nbsp;</b></p>
</th>
</tr>

<tr valign="top">
<th align="center">
<p class="tent"><b>Mode</b></p>
</th>
<th align="center">
<p class="tent"><b>Mode</b></p>
</th>
<th align="center">
<p class="tent"><b>Description</b></p>
</th>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VEOF</p>
</td>
<td align="left">
<p class="tent">&nbsp;</p>
</td>
<td align="left">
<p class="tent">EOF character</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VEOL</p>
</td>
<td align="left">
<p class="tent">&nbsp;</p>
</td>
<td align="left">
<p class="tent">EOL character</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VERASE</p>
</td>
<td align="left">
<p class="tent">&nbsp;</p>
</td>
<td align="left">
<p class="tent">ERASE character</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VINTR</p>
</td>
<td align="left">
<p class="tent">VINTR</p>
</td>
<td align="left">
<p class="tent">INTR character</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VKILL</p>
</td>
<td align="left">
<p class="tent">&nbsp;</p>
</td>
<td align="left">
<p class="tent">KILL character</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">&nbsp;</p>
</td>
<td align="left">
<p class="tent">VMIN</p>
</td>
<td align="left">
<p class="tent">MIN value</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VQUIT</p>
</td>
<td align="left">
<p class="tent">VQUIT</p>
</td>
<td align="left">
<p class="tent">QUIT character</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VSUSP</p>
</td>
<td align="left">
<p class="tent">VSUSP</p>
</td>
<td align="left">
<p class="tent">SUSP character</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">&nbsp;</p>
</td>
<td align="left">
<p class="tent">VTIME</p>
</td>
<td align="left">
<p class="tent">TIME value</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VSTART</p>
</td>
<td align="left">
<p class="tent">VSTART</p>
</td>
<td align="left">
<p class="tent">START character</p>
</td>
</tr>

<tr valign="top">
<td align="left">
<p class="tent">VSTOP</p>
</td>
<td align="left">
<p class="tent">VSTOP</p>
</td>
<td align="left">
<p class="tent">STOP character</p>
</td>
</tr>
</table>
</center>

<p>The subscript values are unique, except that the VMIN and VTIME subscripts may have the same values as the VEOF and VEOL
subscripts, respectively.</p>

<p>Implementations that do not support changing the START and STOP characters may ignore the character values in the <i>c_cc</i>
array indexed by the VSTART and VSTOP subscripts when <a href="../functions/tcsetattr.html"><i>tcsetattr</i>()</a> is called, but
shall return the value in use when <a href="../functions/tcgetattr.html"><i>tcgetattr</i>()</a> is called.</p>

<p>The initial values of all control characters are implementation-defined.</p>

<p>If the value of one of the changeable special control characters (see <a href="#tag_11_01_09">Special Characters</a> ) is
_POSIX_VDISABLE, that function shall be disabled; that is, no input data is recognized as the disabled special character. If ICANON
is not set, the value of _POSIX_VDISABLE has no special meaning for the VMIN and VTIME entries of the <i>c_cc</i> array.</p>

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