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<head>
<title>9p-cmdbuf(3) - Plan 9 from User Space</title>
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<tr><td width=20><td>
<tr><td width=20><td><b>9P-CMDBUF(3)</b><td align=right><b>9P-CMDBUF(3)</b>
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<p><font size=+1><b>NAME </b></font><br>
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Cmdbuf, parsecmd, respondcmderror, lookupcmd – control message
parsing<br>
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<p><font size=+1><b>SYNOPSIS </b></font><br>
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<tt><font size=+1>#include <u.h><br>
#include <libc.h><br>
#include <fcall.h><br>
#include <thread.h><br>
#include <9p.h><br>
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typedef struct Cmdbuf<br>
{<br>
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char *buf;<br>
char **f;<br>
int nf;<br>
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} Cmdbuf;<br>
typedef struct Cmdtab<br>
{<br>
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int index;<br>
char *cmd;<br>
int narg;<br>
</table>
};<br>
Cmdbuf *parsecmd(char *p, int n)<br>
Cmdtab *lookupcmd(Cmdbuf *cb, Cmdtab *tab, int ntab)<br>
void respondcmderror(Req *r, Cmdbuf *cb, char *fmt, ...)<br>
</font></tt>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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These data structures and functions provide parsing of textual
control messages.
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<i>Parsecmd</i> treats the <i>n</i> bytes at <i>p</i> (which need not be NUL-terminated)
as a UTF string and splits it using <i>tokenize</i> (see <a href="../man3/getfields.html"><i>getfields</i>(3)</a>).
It returns a <tt><font size=+1>Cmdbuf</font></tt> structure holding pointers to each field in
the message.
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<i>Lookupcmd</i> walks through the array <i>ctab</i>, which has <i>ntab</i> entries,
looking for the first <tt><font size=+1>Cmdtab</font></tt> that matches the parsed command.
(If the parsed command is empty, <i>lookupcmd</i> returns nil immediately.)
A <tt><font size=+1>Cmdtab</font></tt> matches the command if <i>cmd</i> is equal to <i>cb</i><tt><font size=+1>−></font></tt><i>f</i><tt><font size=+1>[0]</font></tt> or if
<i>cmd</i> is <tt><font size=+1>*</font></tt>. Once a matching <tt><font size=+1>Cmdtab</font></tt> has been
found, if <i>narg</i> is not zero, then the parsed command must have
exactly <i>narg</i> fields (including the command string itself). If
the command has the wrong number of arguments, <i>lookupcmd</i> returns
nil. Otherwise, it returns a pointer to the <tt><font size=+1>Cmdtab</font></tt> entry. If <i>lookupcmd</i>
does not find a matching command at all, it returns
nil. Whenever <i>lookupcmd</i> returns nil, it sets the system error
string.
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<i>Respondcmderror</i> resoponds to request <i>r</i> with an error of the form
‘<i>fmt</i>: <i>cmd</i>,’ where <i>fmt</i> is the formatted string and <i>cmd</i> is a reconstruction
of the parsed command. Fmt is often simply <tt><font size=+1>%r .<br>
</font></tt>
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<p><font size=+1><b>EXAMPLES </b></font><br>
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This interface is not used in any distributed 9P servers. It was
lifted from the Plan 9 kernel. Almost any Plan 9 kernel driver
(<tt><font size=+1>/sys/src/9/*/dev*.c</font></tt> on Plan 9) is a good example.<br>
</table>
<p><font size=+1><b>SOURCE </b></font><br>
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<tt><font size=+1>/usr/local/plan9/src/lib9p/parse.c<br>
</font></tt>
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<p><font size=+1><b>SEE ALSO </b></font><br>
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<a href="../man3/9p.html"><i>9p</i>(3)</a><br>
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