| <head> |
| <title>9p(3) - Plan 9 from User Space</title> |
| <meta content="text/html; charset=utf-8" http-equiv=Content-Type> |
| </head> |
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| <table border=0 cellpadding=0 cellspacing=0 width=100%> |
| <tr height=10><td> |
| <tr><td width=20><td> |
| <tr><td width=20><td><b>9P(3)</b><td align=right><b>9P(3)</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> |
| |
| Srv, dirread9p, emalloc9p, erealloc9p, estrdup9p, postfd, postmountsrv, |
| readbuf, readstr, respond, srv, threadpostmountsrv, walkandclone |
| – 9P file service<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> |
| |
| <tt><font size=+1>#include <u.h><br> |
| #include <libc.h><br> |
| #include <fcall.h><br> |
| #include <thread.h><br> |
| #include <9p.h><br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| typedef struct Srv {<br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| Tree* tree;<br> |
| void (*attach)(Req *r);<br> |
| void (*auth)(Req *r);<br> |
| void (*open)(Req *r);<br> |
| void (*create)(Req *r);<br> |
| void (*read)(Req *r);<br> |
| void (*write)(Req *r);<br> |
| void (*remove)(Req *r);<br> |
| void (*flush)(Req *r);<br> |
| void (*stat)(Req *r);<br> |
| void (*wstat)(Req *r);<br> |
| void (*walk)(Req *r);<br> |
| char* (*walk1)(Fid *fid, char *name, Qid *qid);<br> |
| char* (*clone)(Fid *oldfid, Fid *newfid);<br> |
| void (*destroyfid)(Fid *fid);<br> |
| void (*destroyreq)(Req *r);<br> |
| void (*end)(Srv *s);<br> |
| void* aux;<br> |
| int infd;<br> |
| int outfd;<br> |
| int srvfd;<br> |
| int nopipe;<br> |
| |
| </table> |
| } Srv;<br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| int srv(Srv *s)<br> |
| void postmountsrv(Srv *s, char *name, char *mtpt, int flag)<br> |
| void threadpostmountsrv(Srv *s, char *name, char *mtpt, int flag)<br> |
| int postfd(char *srvname, int fd)<br> |
| void respond(Req *r, char *error)<br> |
| ulong readstr(Req *r, char *src)<br> |
| ulong readbuf(Req *r, void *src, ulong nsrc)<br> |
| typedef int Dirgen(int n, Dir *dir, void *aux)<br> |
| void dirread9p(Req *r, Dirgen *gen, void *aux)<br> |
| void walkandclone(Req *r, char *(*walk1)(Fid *old, char *name, |
| void *v),<br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| char *(*clone)(Fid *old, Fid *new, void *v), void *v)<br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| |
| </table> |
| |
| </table> |
| void* emalloc9p(ulong n)<br> |
| void* erealloc9p(void *v, ulong n)<br> |
| char* estrdup9p(char *s)<br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| extern int chatty9p;<br> |
| </font></tt> |
| </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> |
| |
| The function <i>srv</i> serves a 9P session by reading requests from |
| <tt><font size=+1>s−>infd</font></tt>, dispatching them to the function pointers kept in <tt><font size=+1>Srv</font></tt>, |
| and writing the responses to <tt><font size=+1>s−>outfd</font></tt>. (Typically, <i>postmountsrv</i> |
| or <i>threadpostmountsrv</i> initializes the <tt><font size=+1>infd</font></tt> and <tt><font size=+1>outfd</font></tt> structure |
| members. See the description below.) |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| <tt><font size=+1>Req</font></tt> and <tt><font size=+1>Fid</font></tt> structures are allocated one-to-one with uncompleted |
| requests and active fids, and are described in <a href="../man3/9p-fid.html"><i>9p-fid</i>(3)</a>. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| The behavior of <i>srv</i> depends on whether there is a file tree (see |
| <a href="../man3/9p-file.html"><i>9p-file</i>(3)</a>) associated with the server, that is, whether the <tt><font size=+1>tree</font></tt> |
| element is nonzero. The differences are made explicit in the discussion |
| of the service loop below. The <tt><font size=+1>aux</font></tt> element is the client’s, to |
| do with as it pleases. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| <i>Srv</i> does not return until the 9P conversation is finished. Since |
| it is usually run in a separate process so that the caller can |
| exit, the service loop has little chance to return gracefully |
| on out of memory errors. It calls <i>emalloc9p</i>, <i>erealloc9p</i>, and <i>estrdup9p</i> |
| to obtain its memory. The default implementations of these |
| functions act as <i>malloc</i>, <i>realloc</i>, and <i>strdup</i> but abort the program |
| if they run out of memory. If alternate behavior is desired, clients |
| can link against alternate implementations of these functions. |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| <i>Postmountsrv</i> and <i>threadpostmountsrv</i> are wrappers that create a |
| separate process in which to run <i>srv</i>. They do the following:<br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| If <i>s</i><tt><font size=+1>−></font></tt><i>nopipe</i> is zero (the common case), initialize <i>s</i><tt><font size=+1>−></font></tt><i>infd</i> and <i>s</i><tt><font size=+1>−></font></tt><i>outfd</i> |
| to be one end of a freshly allocated pipe, with <i>s</i><tt><font size=+1>−></font></tt><i>srvfd</i> initialized |
| as the other end.<br> |
| If <tt><font size=+1>name</font></tt> is non-nil, call <tt><font size=+1>postfd(</font></tt><i>s</i><tt><font size=+1>−></font></tt><i>srvfd</i><tt><font size=+1>,</font></tt> <i>name</i><tt><font size=+1>)</font></tt> to post <i>s</i><tt><font size=+1>−></font></tt><i>srvfd</i> |
| as <tt><font size=+1>/srv/</font></tt><i>name</i><tt><font size=+1>.<br> |
| </font></tt>Fork a child process via <a href="../man3/rfork.html"><i>rfork</i>(3)</a> or <i>procrfork</i> (see <a href="../man3/thread.html"><i>thread</i>(3)</a>), |
| using the <tt><font size=+1>RFFDG</font></tt>, <tt><font size=+1>RFNAMEG</font></tt>, and <tt><font size=+1>RFMEM</font></tt> flags. The child process calls |
| <i>close(</i><tt><font size=+1>s</font></tt><i>-></i><tt><font size=+1>srvfd</font></tt><i>)</i> and then <i>srv(</i><tt><font size=+1>s</font></tt><i>)</i>; it will exit once <i>srv</i> returns.<br> |
| If <i>mtpt</i> is non-nil, call <tt><font size=+1>amount(</font></tt><i>s</i><tt><font size=+1>−></font></tt><i>srvfd, mtpt</i><tt><font size=+1>,</font></tt> <i>flag</i><tt><font size=+1>, </font></tt>""); otherwise, |
| close <i>s</i><tt><font size=+1>−></font></tt><i>srvfd</i>.<br> |
| The parent returns to the caller. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| |
| </table> |
| If any error occurs during this process, the entire process is |
| terminated by calling <a href="../man3/sysfatal.html"><i>sysfatal</i>(3)</a>.<br> |
| <p><font size=+1><b>Service functions </b></font><br> |
| The functions in a <tt><font size=+1>Srv</font></tt> structure named after 9P transactions are |
| called to satisfy requests as they arrive. If a function is provided, |
| it <i>must</i> arrange for <i>respond</i> to be called when the request is satisfied. |
| The only parameter of each service function is a <tt><font size=+1>Req*</font></tt> parameter |
| (say <i>r</i>). The incoming request parameters are |
| stored in <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i>; <i>r</i><tt><font size=+1>−></font></tt><i>fid</i> and <i>r</i><tt><font size=+1>−></font></tt><i>newfid</i> are pointers to <tt><font size=+1>Fid</font></tt> structures |
| corresponding to the numeric fids in <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i>; similarly, <i>r</i><tt><font size=+1>−></font></tt><i>oldreq</i> |
| is the <tt><font size=+1>Req</font></tt> structure corresponding to <i>r</i><tt><font size=+1>−></font></tt><i>ifcall.oldtag</i>. The outgoing |
| response data should be stored in <i>r</i><tt><font size=+1>−></font></tt><i>ofcall</i>. The one exception |
| to this rule is that <i>stat</i> should fill in |
| <i>r</i><tt><font size=+1>−></font></tt><i>d</i> rather than <i>r</i><tt><font size=+1>−></font></tt><i>ofcall.stat</i>: the library will convert the structure |
| into the machine-independent wire representation. Similarly, <i>wstat</i> |
| may consult <i>r</i><tt><font size=+1>−></font></tt><i>d</i> rather than decoding <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i><tt><font size=+1>.</font></tt><i>stat</i> itself. When |
| a request has been handled, <i>respond</i> should be called with <i>r</i> and |
| an error string. If the request was satisfied |
| successfully, the error string should be a nil pointer. Note that |
| it is permissible for a function to return without itself calling |
| <i>respond</i>, as long as it has arranged for <i>respond</i> to be called at |
| some point in the future by another proc sharing its address space, |
| but see the discussion of <i>flush</i> below. Once <i>respond</i> has been |
| called, the <tt><font size=+1>Req*</font></tt> as well as any pointers it once contained must |
| be considered freed and not referenced. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| If the service loop detects an error in a request (e.g., an attempt |
| to reuse an extant fid, an open of an already open fid, a read |
| from a fid opened for write, etc.) it will reply with an error |
| without consulting the service functions. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| The service loop provided by <i>srv</i> (and indirectly by <i>postmountsrv</i> |
| and <i>threadpostmountsrv</i>) is single-threaded. If it is expected |
| that some requests might block, arranging for alternate processes |
| to handle them is suggested. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| The constraints on the service functions are as follows. These |
| constraints are checked while the server executes. If a service |
| function fails to do something it ought to have, <i>srv</i> will call |
| <i>endsrv</i> and then abort.<br> |
| <i>Auth</i> If authentication is desired, the <i>auth</i> function should record |
| that <i>afid</i> is the new authentication fid and set <i>afid->qid</i> and <i>ofcall.qid</i>. |
| <i>Auth</i> may be nil, in which case it will be treated as having responded |
| with the error “<i>argv0: authentication not required</i>,” where <i>argv0</i> |
| is the program name variable as set by |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| <i>ARGBEGIN</i> (see <a href="../man3/arg.html"><i>arg</i>(3)</a>).<br> |
| |
| </table> |
| <i>Attach</i>The <i>attach</i> function should check the authentication state |
| of <i>afid</i> if desired, and set <i>r</i><tt><font size=+1>−></font></tt><i>fid</i><tt><font size=+1>−></font></tt><i>qid</i> and <i>ofcall.qid</i> to the qid |
| of the file system root. <i>Attach</i> may be nil only if file trees |
| are in use; in this case, the qid will be filled from the root |
| of the tree, and no authentication will be done. |
| <i>Walk</i> If file trees are in use, <i>walk</i> is handled internally, and |
| <i>srv</i><tt><font size=+1>−></font></tt><i>walk</i> is never called.<br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| If file trees are not in use, <i>walk</i> should consult <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i><tt><font size=+1>.</font></tt><i>wname</i> |
| and <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i><tt><font size=+1>.</font></tt><i>nwname</i>, filling in <i>ofcall</i><tt><font size=+1>.</font></tt><i>qid</i> and <i>ofcall</i><tt><font size=+1>.</font></tt><i>nqid</i>, and |
| also copying any necessary <i>aux</i> state from <i>r</i><tt><font size=+1>−></font></tt><i>fid</i> to <i>r</i><tt><font size=+1>−></font></tt><i>newfid</i> when |
| the two are different. As long as <i>walk</i> sets <i>ofcall</i><tt><font size=+1>.</font></tt><i>nqid</i> appropriately, |
| it can <i>respond</i> with a nil error string |
| even when 9P demands an error (<i>e.g.</i>, in the case of a short walk); |
| the library detects error conditions and handles them appropriately.<br> |
| Because implementing the full walk message is intricate and prone |
| to error, the helper routine <i>walkandclone</i> will handle the request |
| given pointers to two functions <i>walk1</i> and (optionally) <i>clone . |
| Clone</i>, if non-nil, is called to signal the creation of <i>newfid</i> |
| from <i>oldfid</i>. Typically a <i>clone</i> routine will copy or increment |
| a reference count in <i>oldfid</i>’s <i>aux</i> element. <i>Walk1</i> should walk <i>fid</i> |
| to <i>name</i>, initializing <i>fid</i><tt><font size=+1>−></font></tt><i>qid</i> to the new path’s qid. Both should |
| return nil on success or an error message on error. <i>Walkandclone</i> |
| will call <i>respond</i> after handling the request.<br> |
| |
| </table> |
| <i>Walk1</i>, <i>Clone<br> |
| </i> |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| If the client provides functions <i>srv</i><tt><font size=+1>−></font></tt><i>walk1</i> and (optionally) <i>srv</i><tt><font size=+1>−></font></tt><i>clone</i>, |
| the 9P service loop will call <i>walkandclone</i> with these functions |
| to handle the request. Unlike the <i>walk1</i> above, <i>srv</i><tt><font size=+1>−></font></tt><i>walk1</i> must |
| fill in both <i>fid</i><tt><font size=+1>−></font></tt><i>qid</i> and <tt><font size=+1>*</font></tt><i>qid</i> with the new qid on a successful |
| walk.<br> |
| |
| </table> |
| <i>Open</i> If file trees are in use, the file metadata will be consulted |
| on open, create, remove, and wstat to see if the requester has |
| the appropriate permissions. If not, an error will be sent back |
| without consulting a service function. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| If not using file trees or the user has the appropriate permissions, |
| <i>open</i> is called with <i>r</i><tt><font size=+1>−></font></tt><i>ofcall</i><tt><font size=+1>.</font></tt><i>qid</i> already initialized to the one |
| stored in the <tt><font size=+1>Fid</font></tt> structure (that is, the one returned in the |
| previous walk). If the qid changes, both should be updated.<br> |
| <i>Create</i>The <i>create</i> function must fill in both <i>r</i><tt><font size=+1>−></font></tt><i>fid</i><tt><font size=+1>−></font></tt><i>qid</i> and <i>r</i><tt><font size=+1>−></font></tt><i>ofcall</i><tt><font size=+1>.</font></tt><i>qid</i> |
| on success. When using file trees, <i>create</i> should allocate a new |
| <tt><font size=+1>File</font></tt> with <i>createfile</i>; note that <i>createfile</i> may return nil (because, |
| say, the file already exists). If the <i>create</i> function is nil, |
| <i>srv</i> behaves as though it were a function that always |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| responded with the error “create prohibited”.<br> |
| |
| </table> |
| <i>Remove<br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| Remove |
| </table> |
| </i> |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| should mark the file as removed, whether by calling <i>removefile</i> |
| when using file trees, or by updating an internal data structure. |
| In general it is not a good idea to clean up the <i>aux</i> information |
| associated with the corresponding <tt><font size=+1>File</font></tt> at this time, to avoid |
| memory errors if other fids have references to that |
| file. Instead, it is suggested that <i>remove</i> simply mark the file |
| as removed (so that further operations on it know to fail) and |
| wait until the file tree’s destroy function is called to reclaim |
| the <i>aux</i> pointer. If not using file trees, it is prudent to take |
| the analogous measures. If <i>remove</i> is not provided, all remove |
| requests will draw “remove prohibited” errors.<br> |
| |
| </table> |
| <i>Read</i> The <i>read</i> function must be provided; it fills <i>r</i><tt><font size=+1>−></font></tt><i>ofcall</i><tt><font size=+1>.</font></tt><i>data</i> |
| with at most <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i><tt><font size=+1>.</font></tt><i>count</i> bytes of data from offset <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i><tt><font size=+1>.</font></tt><i>offset</i> |
| of the file. It also sets <i>r</i><tt><font size=+1>−></font></tt><i>ofcall</i><tt><font size=+1>.</font></tt><i>count</i> to the number of bytes |
| being returned. If using file trees, <i>srv</i> will handle reads of |
| directories internally, only calling <i>read</i> for requests on |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| files. <i>Readstr</i> and <i>readbuf</i> are useful for satisfying read requests |
| on a string or buffer. Consulting the request in <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i>, they |
| fill <i>r</i><tt><font size=+1>−></font></tt><i>ofcall</i><tt><font size=+1>.</font></tt><i>data</i> and set <i>r</i><tt><font size=+1>−></font></tt><i>ofcall</i><tt><font size=+1>.</font></tt><i>count</i>; they do not call <i>respond</i><tt><font size=+1>.</font></tt> |
| Similarly, <i>dirread9p</i> can be used to handle directory reads in |
| servers not using file trees. The passed <i>gen |
| </i>function will be called as necessary to fill <i>dir</i> with information |
| for the <i>n</i>th entry in the directory. The string pointers placed |
| in <i>dir</i> should be fresh copies made with <i>estrdup9p</i>; they will be |
| freed by <i>dirread9p</i> after each successful call to <i>gen</i>. <i>Gen</i> should |
| return zero if it successfully filled <i>dir</i>, minus one on end of |
| directory.<br> |
| |
| </table> |
| <i>Write</i>The <i>write</i> function is similar but need not be provided. If |
| it is not, all writes will draw “write prohibited” errors. Otherwise, |
| <i>write</i> should attempt to write the <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i><tt><font size=+1>.</font></tt><i>count</i> bytes of <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i><tt><font size=+1>.</font></tt><i>data</i> |
| to offset <i>r</i><tt><font size=+1>−></font></tt><i>ifcall</i><tt><font size=+1>.</font></tt><i>offset</i> of the file, setting <i>r</i><tt><font size=+1>−></font></tt><i>ofcall</i><tt><font size=+1>.</font></tt><i>count</i> |
| to the number of bytes actually written. Most |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| programs consider it an error to write less than the requested |
| amount.<br> |
| |
| </table> |
| <i>Stat Stat</i> should fill <i>r</i><tt><font size=+1>−></font></tt><i>d</i> with the stat information for <i>r</i><tt><font size=+1>−></font></tt><i>fid</i>. |
| If using file trees, <i>r</i><tt><font size=+1>−></font></tt><i>d</i> will have been initialized with the stat |
| info from the tree, and <i>stat</i> itself may be nil.<br> |
| <i>Wstat</i>The <i>wstat</i> consults <i>r</i><tt><font size=+1>−></font></tt><i>d</i> in changing the metadata for <i>r</i><tt><font size=+1>−></font></tt><i>fid</i> |
| as described in <i>stat</i>(9p). When using file trees, <i>srv</i> will take |
| care to check that the request satisfies the permissions outlined |
| in <i>stat</i>(9p). Otherwise <i>wstat</i> should take care to enforce permissions |
| where appropriate.<br> |
| <i>Flush</i> Single-threaded servers, which always call <i>respond</i> before |
| returning from the service functions, need not provide a <i>flush</i> |
| implementation: <i>flush</i> is only necessary in multithreaded programs, |
| which arrange for <i>respond</i> to be called asynchronously. <i>Flush</i> should |
| cause the request <i>r</i><tt><font size=+1>−></font></tt><i>oldreq</i> to be cancelled or |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| hurried along. If <i>oldreq</i> is cancelled, this should be signalled |
| by calling <i>respond</i> on <i>oldreq</i> with error string ‘<tt><font size=+1>interrupted</font></tt>’. |
| <i>Flush</i> must respond to <i>r</i> with a nil error string. <i>Flush</i> may respond |
| to <i>r</i> before forcing a response to <i>r</i><tt><font size=+1>−></font></tt><i>oldreq</i>. In this case, the |
| library will delay sending the <i>Rflush</i> message until the |
| response to <i>r</i><tt><font size=+1>−></font></tt><i>oldreq</i> has been sent. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| |
| </table> |
| <i>Destroyfid</i>, <i>destroyreq</i>, and <i>end</i> are auxiliary functions, not called |
| in direct response to 9P requests.<br> |
| <i>Destroyfid<br> |
| </i> |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| When a <tt><font size=+1>Fid</font></tt>’s reference count drops to zero (<i>i.e.,</i> it has been |
| clunked and there are no outstanding requests referring to it), |
| <i>destroyfid</i> is called to allow the program to dispose of the <i>fid</i><tt><font size=+1>−></font></tt><i>aux</i> |
| pointer.<br> |
| |
| </table> |
| <i>Destroyreq<br> |
| </i> |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| Similarly, when a <tt><font size=+1>Req</font></tt>’s reference count drops to zero (<i>i.e.</i>, it |
| has been handled via <i>respond</i> and other outstanding pointers to |
| it have been closed), <i>destroyreq</i> is called to allow the program |
| to dispose of the <i>r</i><tt><font size=+1>−></font></tt><i>aux</i> pointer.<br> |
| |
| </table> |
| <i>End</i> Once the 9P service loop has finished (end of file been reached |
| on the service pipe or a bad message has been read), <i>end</i> is called |
| (if provided) to allow any final cleanup. For example, it was |
| used by the Palm Pilot synchronization file system (never finished) |
| to gracefully terminate the serial conversation once the |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| file system had been unmounted. After calling <i>end</i>, the service |
| loop (which runs in a separate process from its caller) terminates |
| using <i>_exits</i> (see <a href="../man3/exits.html"><i>exits</i>(3)</a>). |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| |
| </table> |
| If the <tt><font size=+1>chatty9p</font></tt> flag is at least one, a transcript of the 9P session |
| is printed on standard error. If the <tt><font size=+1>chatty9p</font></tt> flag is greater |
| than one, additional unspecified debugging output is generated. |
| By convention, servers written using this library accept the <tt><font size=+1>−D</font></tt> |
| option to increment <tt><font size=+1>chatty9p</font></tt>. |
| |
| </table> |
| <p><font size=+1><b>EXAMPLES </b></font><br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| <tt><font size=+1>/usr/local/plan9/src/lib9p/ramfs.c</font></tt> is an example of a simple single-threaded |
| file server. On Plan 9, see <i>archfs</i>, <i>cdfs</i>, <i>nntpfs</i>, <i>webfs</i>, and <i>sshnet</i> |
| for more examples. |
| <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> |
| |
| In general, the <tt><font size=+1>File</font></tt> interface is appropriate for maintaining |
| arbitrary file trees (as in <i>ramfs</i>). The <tt><font size=+1>File</font></tt> interface is best |
| avoided when the tree structure is easily generated as necessary; |
| this is true when the tree is highly structured (as in <i>cdfs</i> and |
| <i>nntpfs</i>) or is maintained elsewhere.<br> |
| |
| </table> |
| <p><font size=+1><b>SOURCE </b></font><br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| <tt><font size=+1>/usr/local/plan9/src/lib9p<br> |
| </font></tt> |
| </table> |
| <p><font size=+1><b>SEE ALSO </b></font><br> |
| |
| <table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> |
| |
| <a href="../man3/9p-fid.html"><i>9p-fid</i>(3)</a>, <a href="../man3/9p-file.html"><i>9p-file</i>(3)</a>, <i>intro</i>(9p)<br> |
| |
| </table> |
| |
| <td width=20> |
| <tr height=20><td> |
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