putmsg.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>putmsg</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_007_1786"> </a>NAME</h4><blockquote>putmsg, putpmsg - send a message on a STREAM</blockquote><h4><a name = "tag_000_007_1787"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="stropts.h.html">stropts.h</a>>int putmsg(int <i>fildes</i>, const struct strbuf *<i>ctlptr</i>, const struct strbuf *<i>dataptr</i>, int <i>flags</i>);int putpmsg(int <i>fildes</i>, const struct strbuf *<i>ctlptr</i>, const struct strbuf *<i>dataptr</i>, int <i>band</i>, int <i>flags</i>);</code></pre></blockquote><h4><a name = "tag_000_007_1788"> </a>DESCRIPTION</h4><blockquote>The<i>putmsg()</i>function creates a message from a process buffer(s) and sends the message to aSTREAMS file. The message may contain either a data part, a control part, orboth. The data and control parts are distinguished by placement in separatebuffers, as described below. The semantics of each part is defined by theSTREAMS module that receives the message.<p>The<i>putpmsg()</i>function does the same thing as<i>putmsg()</i>,but the process can send messages in different priority bands. Except wherenoted, all requirements on<i>putmsg()</i>also pertain to<i>putpmsg()</i>.<p>The <i>fildes</i> argument specifies a file descriptor referencing anopen STREAM.The <i>ctlptr</i> and <i>dataptr</i> arguments each point to a <b>strbuf</b>structure.<p>The <i>ctlptr</i> argument points to the structure describing the control part,if any, to be included in the message. The <i>buf</i> member in the<b>strbuf</b> structure points to the buffer where the control informationresides, and the <i>len</i> member indicates the number of bytes to be sent.The <i>maxlen</i> member is not used by<i>putmsg()</i>.In a similar manner, the argument <i>dataptr</i> specifies the data, if any, tobe included in the message. The <i>flags</i> argument indicates what type ofmessage should be sent and is described further below.<p>To send the data part of a message, <i>dataptr</i> must not be a null pointerand the <i>len</i> member of <i>dataptr</i> must be 0 or greater.To send the control part of a message, the corresponding values must be setfor <i>ctlptr</i>. No data (control) part will be sent if either <i>dataptr</i>(<i>ctlptr</i>) is a null pointer or the <i>len</i> member of <i>dataptr</i>(<i>ctlptr</i>) is set to -1.<p>For<i>putmsg()</i>,if a control part is specified and <i>flags</i> is set to RS_HIPRI, a highpriority message is sent. If no control part is specified, and <i>flags</i> isset to RS_HIPRI,<i>putmsg()</i>fails and sets <i>errno</i> to [EINVAL]. If <i>flags</i> is set to 0, a normalmessage (priority band equal to 0) is sent. If a control part and data partare not specified and <i>flags</i> is set to 0, no message is sent and 0 isreturned.<p>For<i>putpmsg()</i>,the flags are different. The <i>flags</i> argument is a bitmask with thefollowing mutually-exclusive flags defined: MSG_HIPRI and MSG_BAND. If<i>flags</i> is set to 0,<i>putpmsg()</i>fails and sets <i>errno</i> to [EINVAL].If a control part is specified and <i>flags</i> is set to MSG_HIPRIand <i>band</i> is set to 0, a high-priority message is sent.If <i>flags</i> is set to MSG_HIPRI and either no control part isspecified or <i>band</i> is set to a non-zero value,<i>putpmsg()</i>fails and sets <i>errno</i> to [EINVAL]. If <i>flags</i> is set to MSG_BAND,then a message is sent in the priority band specified by <i>band</i>. If acontrol part and data part are not specified and <i>flags</i> is set toMSG_BAND, no message is sent and 0 is returned.<p>The<i>putmsg()</i>function blocks if the STREAM write queue is full due to internal flow controlconditions, with the following exceptions:<ul><p><li>For high-priority messages,<i>putmsg()</i>does not block on this condition and continues processing the message.<p><li>For other messages,<i>putmsg()</i>does not block but fails when the write queue is full and O_NONBLOCK is set.<p></ul><p>The<i>putmsg()</i>function also blocks, unless prevented by lack of internal resources, whilewaiting for the availability of message blocks in the STREAM, regardless ofpriority or whether O_NONBLOCK has been specified. No partial message issent.</blockquote><h4><a name = "tag_000_007_1789"> </a>RETURN VALUE</h4><blockquote>Upon successful completion,<i>putmsg()</i>and<i>putpmsg()</i>return 0. Otherwise, they return-1 and set <i>errno</i> to indicate the error.</blockquote><h4><a name = "tag_000_007_1790"> </a>ERRORS</h4><blockquote>The<i>putmsg()</i>and<i>putpmsg()</i>functions will fail if:<dl compact><dt>[EAGAIN]<dd>A non-priority message was specified, the O_NONBLOCK flag is set, and theSTREAM write queue is full due to internal flow control conditions; orbuffers could not be allocated for the message that was to be created.<dt>[EBADF]<dd><i>fildes</i> is not a valid file descriptor open for writing.<dt>[EINTR]<dd>A signal was caught during<i>putmsg()</i>.<dt>[EINVAL]<dd>An undefined value is specified in <i>flags</i>, or <i>flags</i>is set to RS_HIPRI or MSG_HIPRI and no control part is supplied,or the STREAM or multiplexer referenced by<i>fildes</i> is linked (directly or indirectly) downstream from a multiplexer,or <i>flags</i> is set to MSG_HIPRI and <i>band</i>is non-zero (for<i>putpmsg()</i>only).<dt>[ENOSR]<dd>Buffers could not be allocated for the message that was to be created due toinsufficient STREAMS memory resources.<dt>[ENOSTR]<dd>A STREAM is not associated with <i>fildes</i>.<dt>[ENXIO]<dd>A hangup condition was generated downstream for the specified STREAM.<dt>[EPIPE] or [EIO]<dd>The <i>fildes</i> argument refers to a STREAMS-based pipe and the other end ofthe pipe is closed. A SIGPIPE signal is generated for the calling thread.<dt>[ERANGE]<dd>The size of the data part of the message does not fall within the rangespecified by the maximum and minimum packet sizes of the topmost STREAMmodule. This value is also returned if the control part of the message islarger than the maximum configured size of the control part of a message, orif the data part of a message is larger than the maximum configured size ofthe data part of a message.</dl><p>In addition,<i>putmsg()</i>and<i>putpmsg()</i>will fail if the STREAM head had processed an asynchronous error before thecall. In this case, the value of<i>errno</i>does not reflect the result of<i>putmsg()</i>or<i>putpmsg()</i>but reflects the prior error.</blockquote><h4><a name = "tag_000_007_1791"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_1792"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_1793"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_007_1794"> </a>SEE ALSO</h4><blockquote><i><a href="getmsg.html">getmsg()</a></i>,<i><a href="poll.html">poll()</a></i>,<i><a href="read.html">read()</a></i>,<i><a href="write.html">write()</a></i>,<i><a href="stropts.h.html"><stropts.h></a></i>,<a href="STREAMS.html">STREAMS overview</a>.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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