98 lines
4.8 KiB
HTML
98 lines
4.8 KiB
HTML
<head>
|
|
<title>flush(9P) - Plan 9 from User Space</title>
|
|
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
|
|
</head>
|
|
<body bgcolor=#ffffff>
|
|
<table border=0 cellpadding=0 cellspacing=0 width=100%>
|
|
<tr height=10><td>
|
|
<tr><td width=20><td>
|
|
<tr><td width=20><td><b>FLUSH(9P)</b><td align=right><b>FLUSH(9P)</b>
|
|
<tr><td width=20><td colspan=2>
|
|
<br>
|
|
<p><font size=+1><b>NAME </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
flush – abort a message<br>
|
|
|
|
</table>
|
|
<p><font size=+1><b>SYNOPSIS </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
<i>size</i>[4] <tt><font size=+1>Tflush</font></tt> <i>tag</i>[2] <i>oldtag</i>[2]<br>
|
|
<i>size</i>[4] <tt><font size=+1>Rflush</font></tt> <i>tag</i>[2]<br>
|
|
|
|
</table>
|
|
<p><font size=+1><b>DESCRIPTION </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
When the response to a request is no longer needed, such as when
|
|
a user interrupts a process doing a <i>read</i>(9p), a <tt><font size=+1>Tflush</font></tt> request
|
|
is sent to the server to purge the pending response. The message
|
|
being flushed is identified by <i>oldtag</i>. The semantics of <tt><font size=+1>flush</font></tt>
|
|
depends on messages arriving in order.
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
|
|
The server should answer the <tt><font size=+1>flush</font></tt> message immediately. If it
|
|
recognizes <i>oldtag</i> as the tag of a pending transaction, it should
|
|
abort any pending response and discard that tag. In either case,
|
|
it should respond with an <tt><font size=+1>Rflush</font></tt> echoing the <i>tag</i> (not <i>oldtag</i>)
|
|
of the <tt><font size=+1>Tflush</font></tt> message. A <tt><font size=+1>Tflush</font></tt> can never be
|
|
responded to by an <tt><font size=+1>Rerror</font></tt> message.
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
|
|
The server may respond to the pending request before responding
|
|
to the <tt><font size=+1>Tflush</font></tt>. It is possible for a client to send multiple <tt><font size=+1>Tflush</font></tt>
|
|
messages for a particular pending request. Each subsequent <tt><font size=+1>Tflush</font></tt>
|
|
must contain as <i>oldtag</i> the tag of the pending request (not a previous
|
|
<tt><font size=+1>Tflush</font></tt>). Should multiple <tt><font size=+1>Tflush</font></tt>es be
|
|
received for a pending request, they must be answered in order.
|
|
A <tt><font size=+1>Rflush</font></tt> for any of the multiple <tt><font size=+1>Tflush</font></tt>es implies an answer for
|
|
all previous ones. Therefore, should a server receive a request
|
|
and then multiple flushes for that request, it need respond only
|
|
to the last flush.
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
|
|
When the client sends a <tt><font size=+1>Tflush</font></tt>, it must wait to receive the corresponding
|
|
<tt><font size=+1>Rflush</font></tt> before reusing <i>oldtag</i> for subsequent messages. If a response
|
|
to the flushed request is received before the <tt><font size=+1>Rflush</font></tt>, the client
|
|
must honor the response as if it had not been flushed, since the
|
|
completed request may signify a state
|
|
change in the server. For instance, <tt><font size=+1>Tcreate</font></tt> may have created a
|
|
file and <tt><font size=+1>Twalk</font></tt> may have allocated a fid. If no response is received
|
|
before the <tt><font size=+1>Rflush</font></tt>, the flushed transaction is considered to have
|
|
been canceled, and should be treated as though it had never been
|
|
sent.
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
|
|
Several exceptional conditions are handled correctly by the above
|
|
specification: sending multiple flushes for a single tag, flushing
|
|
after a transaction is completed, flushing a <tt><font size=+1>Tflush</font></tt>, and flushing
|
|
an invalid tag.<br>
|
|
|
|
</table>
|
|
<p><font size=+1><b>ENTRY POINTS </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
The <a href="../man3/9pclient.html"><i>9pclient</i>(3)</a> library does not generate <tt><font size=+1>flush</font></tt> transactions..
|
|
<a href="../man4/9pserve.html"><i>9pserve</i>(4)</a> generates <tt><font size=+1>flush</font></tt> transactions to cancel transactions
|
|
pending when a client hangs up.<br>
|
|
|
|
</table>
|
|
|
|
<td width=20>
|
|
<tr height=20><td>
|
|
</table>
|
|
<!-- TRAILER -->
|
|
<table border=0 cellpadding=0 cellspacing=0 width=100%>
|
|
<tr height=15><td width=10><td><td width=10>
|
|
<tr><td><td>
|
|
<center>
|
|
<a href="../../"><img src="../../dist/spaceglenda100.png" alt="Space Glenda" border=1></a>
|
|
</center>
|
|
</table>
|
|
<!-- TRAILER -->
|
|
</body></html>
|