The type.I filename is used for  passing file names  or  pathname components..LP.KS.NH 3\&path.IX "NFS data types" path "" \fIpath\fP.DStypedef string path<MAXPATHLEN>;.DE.KEThe type.I path is a pathname.  The server considers it as a stringwith no internal structure,  but to the client  it is the name of anode in a filesystem tree..LP.KS.NH 3\&attrstat.IX "NFS data types" attrstat "" \fIattrstat\fP.DSunion attrstat switch (stat status) {	case NFS_OK:		fattr attributes;	default:		void;};.DE.KEThe .I attrstat structure is a common procedure result.  It containsa  "status" and,  if  the call   succeeded,   it also contains  theattributes of the file on which the operation was done..LP.KS.NH 3\&diropargs.IX "NFS data types" diropargs "" \fIdiropargs\fP.DSstruct diropargs {	fhandle  dir;	filename name;};.DE.KEThe  .I diropargs structure is used  in  directory  operations.  The"fhandle" "dir" is the directory in  which to find the file "name".A directory operation is one in which the directory is affected..LP.KS.NH 3\&diropres.IX "NFS data types" diropres "" \fIdiropres\fP.DSunion diropres switch (stat status) {	case NFS_OK:		struct {			fhandle file;			fattr   attributes;		} diropok;	default:		void;};.DE.KEThe results of a directory operation  are returned  in a .I diropres structure.  If the call succeeded, a new file handle "file" and the"attributes" associated with that file are  returned along with the"status"..NH 2\&Server Procedures.IX "NFS server procedures" "" "" "" PAGE MAJOR.LPThe  protocol definition  is given as   a  set  of  procedures witharguments  and results defined using the   RPC  language.   A briefdescription of the function of each procedure should provide enoughinformation to allow implementation..LPAll of  the procedures  in   the NFS  protocol  are assumed  to  besynchronous.   When a procedure  returns to the  client, the clientcan assume that the operation has completed and any data associatedwith the request is  now on stable storage.  For  example, a client.I WRITE request   may  cause  the   server  to  update  data  blocks,filesystem information blocks (such as indirect  blocks),  and fileattribute  information (size  and  modify  times).  When  the .I WRITE returns to the client, it can assume  that the write  is safe, evenin case of  a server  crash, and  it can discard the  data written.This is a very important part  of the statelessness  of the server.If the server waited to flush data from remote requests, the clientwould have to  save those requests so that  it could resend them incase of a server crash..ie t .DS.el .DS L.ft I/** Remote file service routines*/.ft CWprogram NFS_PROGRAM {	version NFS_VERSION {		void        NFSPROC_NULL(void)              = 0;		attrstat    NFSPROC_GETATTR(fhandle)        = 1;		attrstat    NFSPROC_SETATTR(sattrargs)      = 2;		void        NFSPROC_ROOT(void)              = 3;		diropres    NFSPROC_LOOKUP(diropargs)       = 4;		readlinkres NFSPROC_READLINK(fhandle)       = 5;		readres     NFSPROC_READ(readargs)          = 6;		void        NFSPROC_WRITECACHE(void)        = 7;		attrstat    NFSPROC_WRITE(writeargs)        = 8;		diropres    NFSPROC_CREATE(createargs)      = 9;		stat        NFSPROC_REMOVE(diropargs)       = 10;		stat        NFSPROC_RENAME(renameargs)      = 11;		stat        NFSPROC_LINK(linkargs)          = 12;		stat        NFSPROC_SYMLINK(symlinkargs)    = 13;		diropres    NFSPROC_MKDIR(createargs)       = 14;		stat        NFSPROC_RMDIR(diropargs)        = 15;		readdirres  NFSPROC_READDIR(readdirargs)    = 16;		statfsres   NFSPROC_STATFS(fhandle)         = 17;	} = 2;} = 100003;.DE.KS.NH 3\&Do Nothing.IX "NFS server procedures" NFSPROC_NULL() "" \fINFSPROC_NULL()\fP.DSvoid NFSPROC_NULL(void) = 0;.DE.KEThis procedure does no work.   It is made available  in  all RPCservices to allow server response testing and timing..KS.NH 3\&Get File Attributes.IX "NFS server procedures" NFSPROC_GETATTR() "" \fINFSPROC_GETATTR()\fP.DSattrstat NFSPROC_GETATTR (fhandle) = 1;.DE.KEIf the reply  status is .I NFS_OK ,then  the reply attributes containsthe attributes for the file given by the input fhandle..KS.NH 3\&Set File Attributes.IX "NFS server procedures" NFSPROC_SETATTR() "" \fINFSPROC_SETATTR()\fP.DSstruct sattrargs {	fhandle file;	sattr attributes;	};attrstatNFSPROC_SETATTR (sattrargs) = 2;.DE.KEThe  "attributes" argument  contains fields which are either  -1 orare  the  new value for  the  attributes of  "file".   If the replystatus is .I NFS_OK ,then the  reply attributes have the attributes ofthe file after the "SETATTR" operation has completed..LPNote: The use of -1 to indicate an unused field in "attributes" ischanged in the next version of the protocol..KS.NH 3\&Get Filesystem Root.IX "NFS server procedures" NFSPROC_ROOT "" \fINFSPROC_ROOT\fP.DSvoid NFSPROC_ROOT(void) = 3;.DE.KEObsolete.  This procedure  is no longer used   because  finding theroot file handle of a filesystem requires moving  pathnames betweenclient  and server.  To  do  this right we would  have  to define anetwork standard representation of pathnames.  Instead, thefunction  of  looking up  the   root  file handle  is  done  by the.I MNTPROC_MNT() procedure.    (See the.I "Mount Protocol Definition"later in this chapter for details)..KS.NH 3\&Look Up File Name.IX "NFS server procedures" NFSPROC_LOOKUP() "" \fINFSPROC_LOOKUP()\fP.DSdiropresNFSPROC_LOOKUP(diropargs) = 4;.DE.KEIf  the reply "status"  is .I NFS_OK ,then the reply  "file" and reply"attributes" are the file handle and attributes for the file "name"in the directory given by "dir" in the argument..KS.NH 3\&Read From Symbolic Link.IX "NFS server procedures" NFSPROC_READLINK() "" \fINFSPROC_READLINK()\fP.DSunion readlinkres switch (stat status) {	case NFS_OK:		path data;	default:		void;};readlinkresNFSPROC_READLINK(fhandle) = 5;.DE.KEIf "status" has the value .I NFS_OK ,then the reply "data" is the data in the symbolic link given by the file referred to by the fhandle argument..LPNote:  since   NFS always  parses pathnames    on the  client, thepathname in  a symbolic  link may  mean something  different (or bemeaningless) on a different client or on the server if  a differentpathname syntax is used..KS.NH 3\&Read From File.IX "NFS server procedures" NFSPROC_READ "" \fINFSPROC_READ\fP.DSstruct readargs {	fhandle file;	unsigned offset;	unsigned count;	unsigned totalcount;};union readres switch (stat status) {	case NFS_OK:		fattr attributes;		opaque data<NFS_MAXDATA>;	default:		void;};readresNFSPROC_READ(readargs) = 6;.DE.KEReturns  up  to  "count" bytes of   "data" from  the file  given by"file", starting at "offset" bytes from  the beginning of the file.The first byte of the file is  at offset zero.  The file attributesafter the read takes place are returned in "attributes"..LPNote: The  argument "totalcount" is  unused, and is removed in thenext protocol revision..KS.NH 3\&Write to Cache.IX "NFS server procedures" NFSPROC_WRITECACHE() "" \fINFSPROC_WRITECACHE()\fP.DSvoidNFSPROC_WRITECACHE(void) = 7;.DE.KETo be used in the next protocol revision..KS.NH 3\&Write to File.IX "NFS server procedures" NFSPROC_WRITE() "" \fINFSPROC_WRITE()\fP.DSstruct writeargs {	fhandle file;          	unsigned beginoffset;  	unsigned offset;       	unsigned totalcount;   	opaque data<NFS_MAXDATA>;};attrstat	NFSPROC_WRITE(writeargs) = 8;.DE.KEWrites   "data" beginning  "offset"  bytes  from the  beginning  of"file".  The first byte  of  the file is at  offset  zero.  If  thereply "status" is NFS_OK, then  the reply "attributes" contains theattributes  of the file after the  write has  completed.  The writeoperation is atomic.  Data from this  call to .I WRITE will not be mixed with data from another client's calls..LPNote: The arguments "beginoffset" and "totalcount" are ignored andare removed in the next protocol revision..KS.NH 3\&Create File.IX "NFS server procedures" NFSPROC_CREATE() "" \fINFSPROC_CREATE()\fP.DSstruct createargs {	diropargs where;	sattr attributes;};diropresNFSPROC_CREATE(createargs) = 9;.DE.KEThe file "name" is created  in the directory given  by "dir".   Theinitial  attributes of the  new file  are given by "attributes".  Areply "status"  of NFS_OK indicates that the  file was created, andreply "file"   and   reply "attributes"  are    its file handle andattributes.   Any  other reply  "status"  means that  the operationfailed and no file was created..LPNote: This  routine should pass  an exclusive create flag, meaning"create the file only if it is not already there"..KS.NH 3\&Remove File.IX "NFS server procedures" NFSPROC_REMOVE() "" \fINFSPROC_REMOVE()\fP.DSstatNFSPROC_REMOVE(diropargs) = 10;.DE.KEThe file "name" is  removed from the directory  given by "dir".   Areply of NFS_OK means the directory entry was removed..LPNote: possibly non-idempotent operation..KS.NH 3\&Rename File.IX "NFS server procedures" NFSPROC_RENAME() "" \fINFSPROC_RENAME()\fP.DSstruct renameargs {	diropargs from;		diropargs to;};statNFSPROC_RENAME(renameargs) = 11;.DE.KEThe existing file "from.name" in  the directory given by "from.dir"is renamed to "to.name" in the directory given by "to.dir".  If thereply  is .I NFS_OK ,the file was  renamed.  The  RENAME  operation isatomic on the server; it cannot be interrupted in the middle..LPNote: possibly non-idempotent operation..KS.NH 3\&Create Link to File.IX "NFS server procedures" NFSPROC_LINK() "" \fINFSPROC_LINK()\fP.DSstruct linkargs {	fhandle from;	diropargs to;};statNFSPROC_LINK(linkargs) = 12;.DE.KECreates the  file "to.name"  in the directory  given   by "to.dir",which is a hard link to the existing file given  by "from".  If thereturn value is .I NFS_OK ,a link was created.  Any other return valueindicates an error, and the link was not created..LPA hard link should have the property that changes  to either of thelinked files are reflected in both files.  When a hard link is madeto a  file, the attributes  for  the file should  have  a value for"nlink" that is one greater than the value before the link..LPNote: possibly non-idempotent operation..KS.NH 3\&Create Symbolic Link.IX "NFS server procedures" NFSPROC_SYMLINK() "" \fINFSPROC_SYMLINK()\fP.DSstruct symlinkargs {	diropargs from;	path to;	sattr attributes;};statNFSPROC_SYMLINK(symlinkargs) = 13;.DE.KECreates the  file "from.name" with  ftype  .I NFLNK in  the  directorygiven by "from.dir".   The new file contains  the pathname "to" andhas initial attributes given by "attributes".  If  the return valueis .I NFS_OK ,a link was created.  Any other return value indicates anerror, and the link was not created..LPA symbolic  link is  a pointer to another file.   The name given in"to" is  not interpreted by  the server, only stored in  the  newlycreated file.  When the client references a file that is a symboliclink, the contents of the symbolic  link are normally transparentlyreinterpreted  as a pathname  to substitute.   A .I READLINK operation returns the data to the client for interpretation..LPNote:  On UNIX servers the attributes are never used, sincesymbolic links always have mode 0777..KS.NH 3\&Create Directory.IX "NFS server procedures" NFSPROC_MKDIR() "" \fINFSPROC_MKDIR()\fP.DSdiropresNFSPROC_MKDIR (createargs) = 14;.DE.KEThe new directory "where.name" is created in the directory given by"where.dir".  The initial attributes of the new directory are givenby "attributes".  A reply "status" of NFS_OK indicates that the newdirectory was created, and reply "file" and  reply "attributes" areits file  handle and attributes.  Any  other  reply "status"  meansthat the operation failed and no directory was created..LPNote: possibly non-idempotent operation..KS.NH 3\&Remove Directory.IX "NFS server procedures" NFSPROC_RMDIR() "" \fINFSPROC_RMDIR()\fP.DSstatNFSPROC_RMDIR(diropargs) = 15;.DE.KEThe existing empty directory "name" in the directory given by "dir"is removed.  If the reply is .I NFS_OK ,the directory was removed..LPNote: possibly non-idempotent operation..KS.NH 3