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Filesystem(3)			      Tcl Library Procedures			    Filesystem(3)

_________________________________________________________________________________________________

NAME
       Tcl_FSRegister, Tcl_FSUnregister, Tcl_FSData, Tcl_FSMountsChanged, Tcl_FSGetFileSystemFor-
       Path,  Tcl_FSGetPathType,  Tcl_FSCopyFile,   Tcl_FSCopyDirectory,   Tcl_FSCreateDirectory,
       Tcl_FSDeleteFile,  Tcl_FSRemoveDirectory, Tcl_FSRenameFile, Tcl_FSListVolumes, Tcl_FSEval-
       File,  Tcl_FSLoadFile,  Tcl_FSMatchInDirectory,	Tcl_FSLink,   Tcl_FSLstat,   Tcl_FSUtime,
       Tcl_FSFileAttrsGet,  Tcl_FSFileAttrsSet,  Tcl_FSFileAttrStrings, Tcl_FSStat, Tcl_FSAccess,
       Tcl_FSOpenFileChannel,  Tcl_FSGetCwd,  Tcl_FSChdir,  Tcl_FSPathSeparator,  Tcl_FSJoinPath,
       Tcl_FSSplitPath,  Tcl_FSEqualPaths,  Tcl_FSGetNormalizedPath, Tcl_FSJoinToPath, Tcl_FSCon-
       vertToPathType, Tcl_FSGetInternalRep, Tcl_FSGetTranslatedPath,  Tcl_FSGetTranslatedString-
       Path,  Tcl_FSNewNativePath,  Tcl_FSGetNativePath, Tcl_FSFileSystemInfo, Tcl_AllocStatBuf -
       procedures to interact with any filesystem

SYNOPSIS
       #include <tcl.h>

       int
       Tcl_FSRegister(clientData, fsPtr)

       int
       Tcl_FSUnregister(fsPtr)

       ClientData
       Tcl_FSData(fsPtr)

       void
       Tcl_FSMountsChanged(fsPtr)

       Tcl_Filesystem*
       Tcl_FSGetFileSystemForPath(pathObjPtr)

       Tcl_PathType
       Tcl_FSGetPathType(pathObjPtr)

       int
       Tcl_FSCopyFile(srcPathPtr, destPathPtr)

       int
       Tcl_FSCopyDirectory(srcPathPtr, destPathPtr, errorPtr)

       int
       Tcl_FSCreateDirectory(pathPtr)

       int
       Tcl_FSDeleteFile(pathPtr)

       int
       Tcl_FSRemoveDirectory(pathPtr, int recursive, errorPtr)

       int
       Tcl_FSRenameFile(srcPathPtr, destPathPtr)

       Tcl_Obj*
       Tcl_FSListVolumes(void)

       int
       Tcl_FSEvalFile(interp, pathPtr)

       int
       Tcl_FSLoadFile(interp, pathPtr, sym1, sym2, proc1Ptr, proc2Ptr, handlePtr, unloadProcPtr)

       int
       Tcl_FSMatchInDirectory(interp, result, pathPtr, pattern, types)

       Tcl_Obj*
       Tcl_FSLink(linkNamePtr, toPtr, linkAction)

       int
       Tcl_FSLstat(pathPtr, statPtr)

       int
       Tcl_FSUtime(pathPtr, tval)

       int
       Tcl_FSFileAttrsGet(interp, int index, pathPtr, objPtrRef)

       int
       Tcl_FSFileAttrsSet(interp, int index, pathPtr, Tcl_Obj *objPtr)

       CONST char**
       Tcl_FSFileAttrStrings(pathPtr, objPtrRef)

       int
       Tcl_FSStat(pathPtr, statPtr)

       int
       Tcl_FSAccess(pathPtr, mode)

       Tcl_Channel
       Tcl_FSOpenFileChannel(interp, pathPtr, modeString, permissions)

       Tcl_Obj*
       Tcl_FSGetCwd(interp)

       int
       Tcl_FSChdir(pathPtr)

       Tcl_Obj*
       Tcl_FSPathSeparator(pathPtr)

       Tcl_Obj*
       Tcl_FSJoinPath(listObj, elements)

       Tcl_Obj*
       Tcl_FSSplitPath(pathPtr, lenPtr)

       int
       Tcl_FSEqualPaths(firstPtr, secondPtr)

       Tcl_Obj*
       Tcl_FSGetNormalizedPath(interp, pathPtr)

       Tcl_Obj*
       Tcl_FSJoinToPath(basePtr, objc, objv)

       int
       Tcl_FSConvertToPathType(interp, pathPtr)

       ClientData
       Tcl_FSGetInternalRep(pathPtr, fsPtr)

       Tcl_Obj*
       Tcl_FSGetTranslatedPath(interp, pathPtr)

       CONST char*
       Tcl_FSGetTranslatedStringPath(interp, pathPtr)

       Tcl_Obj*
       Tcl_FSNewNativePath(fsPtr, clientData)

       CONST char*
       Tcl_FSGetNativePath(pathPtr)

       Tcl_Obj*
       Tcl_FSFileSystemInfo(pathPtr)

       Tcl_StatBuf*
       Tcl_AllocStatBuf()

ARGUMENTS
       Tcl_Filesystem	*fsPtr	 (in)	   Points to a structure containing the addresses of pro-
					   cedures  that  can  be  called  to perform the various
					   filesystem operations.

       Tcl_Obj		*pathPtr (in)	   The path represented by this object is  used  for  the
					   operation in question.  If the object does not already
					   have an internal path representation, it will be  con-
					   verted to have one.

       Tcl_Obj		*srcPathPtr(in)    As  for  pathPtr,  but  used for the source file for a
					   copy or rename operation.

       Tcl_Obj		*destPathPtr(in)   As for pathPtr, but used for the destination  filename
					   for a copy or rename operation.

       CONST char	*pattern (in)	   Only  files	or directories matching this pattern will
					   be returned by Tcl_FSMatchInDirectory.

       GlobTypeData	*types	 (in)	   Only files or directories matching the  type  descrip-
					   tions  contained in this structure will be returned by
					   Tcl_FSMatchInDirectory.  It is very important that the
					   'directory'	flag is properly handled.  This parameter
					   may be NULL.

       Tcl_Interp	*interp  (in)	   Interpreter to use either for results, evaluation,  or
					   reporting error messages.

       ClientData	clientData(in)	   The native description of the path object to create.

       Tcl_Obj		*firstPtr(in)	   The	first of two path objects to compare.  The object
					   may be converted to path type.

       Tcl_Obj		*secondPtr(in)	   The second of two path objects to compare.  The object
					   may be converted to path type.

       Tcl_Obj		*listObj (in)	   The	list  of  path elements to operate on with a join
					   operation.

       int		elements (in)	   If non-negative, the number of elements in the listObj
					   which  should  be  joined together.	If negative, then
					   all elements are joined.

       Tcl_Obj		**errorPtr(out)    In the case of an error, filled with  an  object  con-
					   taining  the name of the file which caused an error in
					   the various copy/rename operations.

       Tcl_Obj		**objPtrRef(out)   Filled with an object containing  the  result  of  the
					   operation.

       Tcl_Obj		*result  (out)	   Pre-allocated object in which to store (by lappending)
					   the list of files or directories  which  are  success-
					   fully matched in Tcl_FSMatchInDirectory.

       int		mode	 (in)	   Mask consisting of one or more of R_OK, W_OK, X_OK and
					   F_OK.  R_OK, W_OK and X_OK  request	checking  whether
					   the	file  exists  and   has  read, write and  execute
					   permissions, respectively.  F_OK just requests  check-
					   ing for the existence of the file.

       Tcl_StatBuf	*statPtr (out)	   The	structure  that  contains the result of a stat or
					   lstat operation.

       CONST char	*sym1	 (in)	   Name of a procedure to look up in  the  file's  symbol
					   table

       CONST char	*sym2	 (in)	   Name  of  a	procedure to look up in the file's symbol
					   table

       Tcl_PackageInitProc	 **proc1Ptr(out)
					   Filled with the init function for this code.

       Tcl_PackageInitProc	 **proc2Ptr(out)
					   Filled with the safe-init function for this code.

       ClientData	*clientDataPtr(out)
					   Filled with the  clientData	value  to  pass  to  this
					   code's unload function when it is called.

       TclfsUnloadFileProc_	 **unloadProcPtr(out)
					   Filled  with  the function to use to unload this piece
					   of code.

       utimbuf		*tval	 (in)	   The access and modification times  in  this	structure
					   are	read  and  used  to  set those values for a given
					   file.

       CONST char	*modeString(in)    Specifies how the file is to be  accessed.	May  have
					   any of the values allowed for the mode argument to the
					   Tcl open command.

       int		permissions(in)    POSIX-style permission flags such as 0644.  If  a  new
					   file  is created, these permissions will be set on the
					   created file.

       int		*lenPtr  (out)	   If non-NULL, filled with the number of elements in the
					   split path.

       Tcl_Obj		*basePtr (in)	   The	base path on to which to join the given elements.
					   May be NULL.

       int		objc	 (in)	   The number of elements in objv.

       Tcl_Obj *CONST	objv[]	 (in)	   The elements to join to the given base path.
_________________________________________________________________

DESCRIPTION
       There are several reasons for calling the Tcl_FS... functions rather than  calling  system
       level  functions  like access and stat directly.  First, they will work cross-platform, so
       an extension which calls them should work unmodified on Unix, MacOS and Windows.   Second,
       the  Windows implementation of some of these functions fixes some bugs in the system level
       calls.  Third, these function calls deal with any 'Utf to  platform-native'  path  conver-
       sions  which  may  be  required (and may cache the results of such conversions for greater
       efficiency on subsequent calls).  Fourth, and perhaps most importantly, all of these func-
       tions  are  'virtual  filesystem aware'.  Any virtual filesystem which has been registered
       (through Tcl_FSRegister) may reroute file access to alternative media or  access  methods.
       This  means  that all of these functions (and therefore the corresponding file, glob, pwd,
       cd, open, etc.  Tcl commands) may be operate on 'files' which are not native files in  the
       native  filesystem.   This also means that any Tcl extension which accesses the filesystem
       through this API is automatically 'virtual filesystem aware'.  Of course, if an	extension
       accesses  the  native  filesystem  directly (through platform-specific APIs, for example),
       then Tcl cannot intercept such calls.

       If appropriate vfs's have been registered, the 'files'  may,  to  give  two  examples,  be
       remote  (e.g.  situated	on a remote ftp server) or archived (e.g. lying inside a .zip ar-
       chive).	Such registered filesystems provide a lookup table of functions to implement  all
       or  some  of the functionality listed here.  Finally, the Tcl_FSStat and Tcl_FSLstat calls
       abstract away from what the 'struct stat' buffer buffer is actually declared to be, allow-
       ing  the  same  code to be used both on systems with and systems without support for files
       larger than 2GB in size.

       The Tcl_FS... are objectified and may  cache  internal  representations	and  other  path-
       related strings (e.g. the current working directory).  One side-effect of this is that one
       must not pass in objects with a refCount of zero to any of these functions.  If such calls
       were  handled, they might result in memory leaks (under some circumstances, the filesystem
       code may wish to retain a reference to the passed in object, and so one	must  not  assume
       that  after  any  of  these calls return, the object still has a refCount of zero - it may
       have been incremented), or in a direct segfault due to the object  being  freed	part  way
       through	the complex object manipulation required to ensure that the path is fully normal-
       ized and absolute for filesystem determination.	The practical lesson to learn  from  this
       is  that Tcl_Obj *path = Tcl_NewStringObj(...)  ; Tcl_FS...(path) ; Tcl_DecrRefCount(path)
       is wrong, and may segfault.  The 'path' must have its refCount incremented before  passing
       it  in,	or decrementing it.  For this reason, objects with a refCount of zero are consid-
       ered not to be valid filesystem paths and calling any Tcl_FS API with such an object  will
       result in no action being taken.

       Tcl_FSCopyFile  attempts  to  copy  the file given by srcPathPtr to the path name given by
       destPathPtr.  If the two paths given lie in the same filesystem (according  to  Tcl_FSGet-
       FileSystemForPath)  then  that  filesystem's 'copy file' function is called (if it is non-
       NULL).  Otherwise the function returns -1 and sets Tcl's errno to the 'EXDEV' posix  error
       code (which signifies a 'cross-domain link').

       Tcl_FSCopyDirectory  attempts  to  copy the directory given by srcPathPtr to the path name
       given by destPathPtr.  If the two paths given lie in the  same  filesystem  (according  to
       Tcl_FSGetFileSystemForPath)  then  that filesystem's 'copy file' function is called (if it
       is non-NULL).  Otherwise the function returns -1 and sets Tcl's errno to the 'EXDEV' posix
       error code (which signifies a 'cross-domain link').

       Tcl_FSCreateDirectory  attempts	to  create  the directory given by pathPtr by calling the
       owning filesystem's 'create directory' function.

       Tcl_FSDeleteFile attempts to delete the file  given  by	pathPtr  by  calling  the  owning
       filesystem's 'delete file' function.

       Tcl_FSRemoveDirectory  attempts	to  remove  the directory given by pathPtr by calling the
       owning filesystem's 'remove directory' function.

       Tcl_FSRenameFile attempts to rename the file or directory given by srcPathPtr to the  path
       name  given  by destPathPtr.  If the two paths given lie in the same filesystem (according
       to Tcl_FSGetFileSystemForPath) then that filesystem's 'rename file' function is called (if
       it  is  non-NULL).   Otherwise the function returns -1 and sets Tcl's errno to the 'EXDEV'
       posix error code (which signifies a ``cross-domain link'').

       Tcl_FSListVolumes calls each filesystem which has a non-NULL 'list volumes'  function  and
       asks  them  to  return  their list of root volumes.  It accumulates the return values in a
       list which is returned to the caller (with a refCount of 0).

       Tcl_FSEvalFile reads the file given by pathPtr and evaluates its contents as a Tcl script.
       It returns the same information as Tcl_EvalObjEx.  If the file couldn't be read then a Tcl
       error is returned to describe why the file couldn't be read.  The  eofchar  for	files  is
       '\32'  (^Z) for all platforms.  If you require a ``^Z'' in code for string comparison, you
       can use ``\032'' or ``\u001a'', which will be safely substituted by  the  Tcl  interpreter
       into ``^Z''.

       Tcl_FSLoadFile  dynamically loads a binary code file into memory and returns the addresses
       of two procedures within that file, if they are defined.  The appropriate function for the
       filesystem to which pathPtr belongs will be called.  If that filesystem does not implement
       this function (most virtual filesystems will not, because of OS limitations in dynamically
       loading	binary code), Tcl will attempt to copy the file to a temporary directory and load
       that temporary file.

       Returns a standard Tcl completion code.	If an error occurs, an error message is  left  in
       the interp's result.

       Tcl_FSMatchInDirectory  is  used  by the globbing code to search a directory for all files
       which match a given pattern.  The appropriate function for the filesystem to which pathPtr
       belongs will be called.

       The  return  value  is a standard Tcl result indicating whether an error occurred in glob-
       bing.  Error messages are placed in interp, but good results are placed in  the	resultPtr
       given.
			  Note	that the 'glob' code implements recursive patterns internally, so
       this function will only ever be passed simple patterns, which can  be  matched  using  the
       logic of 'string match'.  To handle recursion, Tcl will call this function frequently ask-
       ing only for directories to be returned.

       Tcl_FSLink replaces the library version of readlink(), and extends it to support the  cre-
       ation  of links.  The appropriate function for the filesystem to which linkNamePtr belongs
       will be called.

       If the toPtr is NULL, a readlink action is performed.  The result is a Tcl_Obj  specifying
       the  contents  of the symbolic link given by linkNamePtr, or NULL if the link could not be
       read.  The result is owned by the caller, which	should	call  Tcl_DecrRefCount	when  the
       result  is no longer needed.  If the toPtr is not NULL, Tcl should create a link of one of
       the types passed in in the linkAction flag.  This flag is an or'd combination of  TCL_CRE-
       ATE_SYMBOLIC_LINK  and  TCL_CREATE_HARD_LINK.   Where  a choice exists (i.e. more than one
       flag is passed in), the Tcl convention is to prefer symbolic links.  When a link  is  suc-
       cessfully  created,  the return value should be toPtr (which is therefore already owned by
       the caller).  If unsuccessful, NULL should be returned.

       Tcl_FSLstat fills the stat structure statPtr with information about  the  specified  file.
       You  do not need any access rights to the file to get this information but you need search
       rights to all directories named in the path leading  to	the  file.   The  stat	structure
       includes info regarding device, inode (always 0 on Windows), privilege mode, nlink (always
       1 on Windows), user id (always 0 on Windows), group id (always 0 on Windows),  rdev  (same
       as device on Windows), size, last access time, last modification time, and creation time.

       If  path exists, Tcl_FSLstat returns 0 and the stat structure is filled with data.  Other-
       wise, -1 is returned, and no stat info is given.

       Tcl_FSUtime replaces the library version of utime.

       For results see 'utime' documentation.	If  successful,  the  function	will  update  the
       'atime' and 'mtime' values of the file given.

       Tcl_FSFileAttrsGet  implements  read access for the hookable 'file attributes' subcommand.
       The appropriate function for the filesystem to which pathPtr belongs will be called.

       If the result is TCL_OK, then an object was placed in objPtrRef, which will only be tempo-
       rarily valid (unless Tcl_IncrRefCount is called).

       Tcl_FSFileAttrsSet  implements write access for the hookable 'file attributes' subcommand.
       The appropriate function for the filesystem to which pathPtr belongs will be called.

       Tcl_FSFileAttrStrings implements part of the hookable 'file attributes'	subcommand.   The
       appropriate function for the filesystem to which pathPtr belongs will be called.

       The called procedure may either return an array of strings, or may instead return NULL and
       place a Tcl list into the given objPtrRef.  Tcl will take that list  and  first	increment
       its refCount before using it.  On completion of that use, Tcl will decrement its refCount.
       Hence if the list should be disposed of by Tcl when done, it should  have  a  refCount  of
       zero, and if the list should not be disposed of, the filesystem should ensure it retains a
       refCount on the object.

       Tcl_FSAccess checks whether the process would be allowed to read, write or test for  exis-
       tence of the file (or other file system object) whose name is pathname.	 If pathname is a
       symbolic link on Unix, then permissions of the file referred by	this  symbolic	link  are
       tested.

       On  success (all requested permissions granted), zero is returned.  On error (at least one
       bit in mode asked for a permission that is denied, or some other  error occurred),  -1  is
       returned.

       Tcl_FSStat  fills  the  stat  structure statPtr with information about the specified file.
       You do not need any access rights to the file to get this information but you need  search
       rights  to  all	directories  named  in	the path leading to the file.  The stat structure
       includes info regarding device, inode (always 0 on Windows), privilege mode, nlink (always
       1  on  Windows), user id (always 0 on Windows), group id (always 0 on Windows), rdev (same
       as device on Windows), size, last access time, last modification time, and creation time.

       If path exists, Tcl_FSStat returns 0 and the stat structure is filled with  data.   Other-
       wise, -1 is returned, and no stat info is given.

       Tcl_FSOpenFileChannel  opens a file specified by pathPtr and returns a channel handle that
       can be used to perform input and output on the file. This API is modeled after  the  fopen
       procedure  of  the  Unix standard I/O library.  The syntax and meaning of all arguments is
       similar to those given in the Tcl open command when opening a file.  If	an  error  occurs
       while  opening  the  channel, Tcl_FSOpenFileChannel returns NULL and records a POSIX error
       code that can be retrieved  with  Tcl_GetErrno.	 In  addition,	if  interp  is	non-NULL,
       Tcl_FSOpenFileChannel leaves an error message in interp's result after any error.

       The  newly  created channel is not registered in the supplied interpreter; to register it,
       use Tcl_RegisterChannel, described below.  If one of the standard channels, stdin,  stdout
       or  stderr was previously closed, the act of creating the new channel also assigns it as a
       replacement for the standard channel.

       Tcl_FSGetCwd replaces the library version of getcwd().

       It returns the Tcl library's current working directory.	This  may  be  different  to  the
       native  platform's  working  directory, in the case for which the cwd is not in the native
       filesystem.

       The result is a pointer to a Tcl_Obj specifying the current directory, or NULL if the cur-
       rent  directory could not be determined.  If NULL is returned, an error message is left in
       the interp's result.		       The result already has  its  refCount  incremented
       for  the  caller.  When it is no longer needed, that refCount should be decremented.  This
       is needed for thread-safety purposes, to allow multiple threads to access this and related
       functions, while ensuring the results are always valid.

       Tcl_FSChdir  replaces  the  library  version  of chdir().  The path is normalized and then
       passed to the filesystem which claims it.  If that  filesystem  does  not  implement  this
       function,  Tcl  will  fallback  to  a  combination of stat and access to check whether the
       directory exists and has appropriate permissions.

       For results, see chdir() documentation.	If successful, we keep a record of the successful
       path in cwdPathPtr for subsequent calls to getcwd.

       Tcl_FSPathSeparator  returns  the separator character to be used for most specific element
       of the path specified by pathPtr (i.e. the last part of the path).

       The separator is returned as a Tcl_Obj containing a string of length 1.	If  the  path  is
       invalid, NULL is returned.

       Tcl_FSJoinPath takes the given Tcl_Obj, which should be a valid list, and returns the path
       object given by considering the first 'elements' elements as valid path segments.  If ele-
       ments < 0, we use the entire list.

       Returns object with refCount of zero, containing the joined path.

       Tcl_FSSplitPath	takes  the given Tcl_Obj, which should be a valid path, and returns a Tcl
       List object containing each segment of that path as an element.

       Returns list object with refCount of zero.  If the passed in lenPtr is non-NULL, we use it
       to return the number of elements in the returned list.

       Tcl_FSEqualPaths tests whether the two paths given represent the same filesystem object

       It returns 1 if the paths are equal, and 0 if they are different.  If either path is NULL,
       0 is always returned.

       Tcl_FSGetNormalizedPath this important function attempts to extract from the given Tcl_Obj
       a  unique normalized path representation, whose string value can be used as a unique iden-
       tifier for the file.

       It returns the normalized path object, with refCount of zero, or  NULL  if  the	path  was
       invalid or could otherwise not be successfully converted.  Extraction of absolute, normal-
       ized paths is very efficient (because the filesystem  operates  on  these  representations
       internally),  although the result when the filesystem contains numerous symbolic links may
       not be the most user-friendly version of a path.

       Tcl_FSJoinToPath takes the given object, which should usually be a valid path or NULL, and
       joins onto it the array of paths segments given.

       Returns object with refCount of zero, containing the joined path.

       Tcl_FSConvertToPathType	tries to convert the given Tcl_Obj to a valid Tcl path type, tak-
       ing account of the fact that the cwd may have changed even if this object is already  sup-
       posedly	of the correct type.  The filename may begin with "~" (to indicate current user's
       home directory) or "~<user>" (to indicate any user's home directory).

       If the conversion succeeds (i.e. the object is a valid path in one of the current filesys-
       tems), then TCL_OK is returned.	Otherwise TCL_ERROR is returned, and an error message may
       be left in the interpreter.

       Tcl_FSGetInternalRep extracts the internal representation of a given path object,  in  the
       given  filesystem.   If the path object belongs to a different filesystem, we return NULL.
       If the internal representation is currently NULL, we attempt to generate  it,  by  calling
       the filesystem's Tcl_FSCreateInternalRepProc.

       Returns	NULL  or  a  valid internal path representation.  This internal representation is
       cached, so that repeated calls to this function will not require additional conversions.

       Tcl_FSGetTranslatedPath attempts to extract the translated path from the given Tcl_Obj.

       If the translation succeeds (i.e. the object is a valid path), then it is returned.   Oth-
       erwise  NULL  will  be  returned,  and an error message may be left in the interpreter.	A
       "translated" path is one which contains no "~"  or  "~user"  sequences  (these  have  been
       expanded to their current representation in the filesystem).

       Tcl_FSGetTranslatedStringPath  does  the  same  as  Tcl_FSGetTranslatedPath, but returns a
       character string or NULL.

       Tcl_FSNewNativePath performs something like that reverse of the usual obj->path->nativerep
       conversions.   If  some	code  retrieves  a  path in native form (from, e.g. readlink or a
       native dialog), and that path is to be used at the Tcl level, then calling  this  function
       is an efficient way of creating the appropriate path object type.

       The  resulting object is a pure 'path' object, which will only receive a Utf-8 string rep-
       resentation if that is required by some Tcl code.

       Tcl_FSGetNativePath is for use by the Win/Unix/MacOS native filesystems, so that they  can
       easily retrieve the native (char* or TCHAR*) representation of a path.  This function is a
       convenience wrapper around Tcl_FSGetInternalRep, and assumes the native representation  is
       string-based.  It may be desirable in the future to have non-string-based native represen-
       tations (for example, on MacOS, a representation using a fileSpec of FSRef structure would
       probably  be  more  efficient).	 On Windows a full Unicode representation would allow for
       paths of unlimited length.  Currently the representation is simply a character string con-
       taining the complete, absolute path in the native encoding.

       The  native  representation  is	cached	so  that repeated calls to this function will not
       require additional conversions.

       Tcl_FSFileSystemInfo returns a list of two elements.  The first element is the name of the
       filesystem  (e.g. "native" or "vfs" or "zip" or "prowrap", perhaps), and the second is the
       particular type of the given path within that filesystem (which is filesystem  dependent).
       The  second  element may be empty if the filesystem does not provide a further categoriza-
       tion of files.

       A valid list object is returned, unless the path object is not recognized, when NULL  will
       be returned.

       Tcl_FSGetFileSystemForPath  returns the a pointer to the Tcl_Filesystem which accepts this
       path as valid.

       If no filesystem will accept the path, NULL is returned.

       Tcl_FSGetPathType determines whether the given path is relative to the current  directory,
       relative to the current volume, or absolute.

       It returns one of TCL_PATH_ABSOLUTE, TCL_PATH_RELATIVE, or TCL_PATH_VOLUME_RELATIVE

       Tcl_AllocStatBuf  allocates  a Tcl_StatBuf on the system heap (which may be deallocated by
       being passed to ckfree.)  This allows extensions  to  invoke  Tcl_FSStat  and  Tcl_FSLStat
       without being dependent on the size of the buffer.  That in turn depends on the flags used
       to build Tcl.

TCL_FILESYSTEM
       A filesystem provides a Tcl_Filesystem structure that contains pointers to functions  that
       implement  the  various operations on a filesystem; these operations are invoked as needed
       by the generic layer, which generally occurs through the functions listed above.

       The Tcl_Filesystem structures are manipulated using the following methods.

       Tcl_FSRegister takes a pointer to a filesystem structure and an optional piece of data  to
       associated with that filesystem.  On calling this function, Tcl will attach the filesystem
       to the list of known filesystems, and it will become fully  functional  immediately.   Tcl
       does not check if the same filesystem is registered multiple times (and in general that is
       not a good thing to do).  TCL_OK will be returned.

       Tcl_FSUnregister removes the given filesystem structure from the list  of  known  filesys-
       tems,  if it is known, and returns TCL_OK.  If the filesystem is not currently registered,
       TCL_ERROR is returned.

       Tcl_FSData will return the ClientData  associated  with	the  given  filesystem,  if  that
       filesystem is registered.  Otherwise it will return NULL.

       Tcl_FSMountsChanged  is used to inform the Tcl's core that the set of mount points for the
       given (already registered) filesystem have changed, and that cached  file  representations
       may therefore no longer be correct.

       The Tcl_Filesystem structure contains the following fields:
	      typedef struct Tcl_Filesystem {
		  CONST char *typeName;
		  int structureLength;
		  Tcl_FSVersion version;
		  Tcl_FSPathInFilesystemProc *pathInFilesystemProc;
		  Tcl_FSDupInternalRepProc *dupInternalRepProc;
		  Tcl_FSFreeInternalRepProc *freeInternalRepProc;
		  Tcl_FSInternalToNormalizedProc *internalToNormalizedProc;
		  Tcl_FSCreateInternalRepProc *createInternalRepProc;
		  Tcl_FSNormalizePathProc *normalizePathProc;
		  Tcl_FSFilesystemPathTypeProc *filesystemPathTypeProc;
		  Tcl_FSFilesystemSeparatorProc *filesystemSeparatorProc;
		  Tcl_FSStatProc *statProc;
		  Tcl_FSAccessProc *accessProc;
		  Tcl_FSOpenFileChannelProc *openFileChannelProc;
		  Tcl_FSMatchInDirectoryProc *matchInDirectoryProc;
		  Tcl_FSUtimeProc *utimeProc;
		  Tcl_FSLinkProc *linkProc;
		  Tcl_FSListVolumesProc *listVolumesProc;
		  Tcl_FSFileAttrStringsProc *fileAttrStringsProc;
		  Tcl_FSFileAttrsGetProc *fileAttrsGetProc;
		  Tcl_FSFileAttrsSetProc *fileAttrsSetProc;
		  Tcl_FSCreateDirectoryProc *createDirectoryProc;
		  Tcl_FSRemoveDirectoryProc *removeDirectoryProc;
		  Tcl_FSDeleteFileProc *deleteFileProc;
		  Tcl_FSCopyFileProc *copyFileProc;
		  Tcl_FSRenameFileProc *renameFileProc;
		  Tcl_FSCopyDirectoryProc *copyDirectoryProc;
		  Tcl_FSLstatProc *lstatProc;
		  Tcl_FSLoadFileProc *loadFileProc;
		  Tcl_FSGetCwdProc *getCwdProc;
		  Tcl_FSChdirProc *chdirProc;
	      } Tcl_Filesystem;

       Except  for  the  first three fields in this structure which contain simple data elements,
       all entries contain addresses of functions called by the generic filesystem layer to  per-
       form the complete range of filesystem related actions.

       The many functions in this structure are broken down into three categories: infrastructure
       functions (almost all of which must be implemented), operational functions (which must  be
       implemented  if	a  complete filesystem is provided), and efficiency functions (which need
       only be implemented if they can be done so efficiently, or if they have side-effects which
       are  required  by  the filesystem; Tcl has less efficient emulations it can fall back on).
       It is important to note that, in the current version of Tcl, most of these  fallbacks  are
       only  used  to  handle  commands initiated in Tcl, not in C. What this means is, that if a
       'file rename' command is issued in Tcl, and the relevant filesystem(s)  do  not	implement
       their  Tcl_FSRenameFileProc,  Tcl's  core  will instead fallback on a combination of other
       filesystem functions (it will use Tcl_FSCopyFileProc followed by Tcl_FSDeleteFileProc, and
       if  Tcl_FSCopyFileProc  is  not	implemented  there is a further fallback).  However, if a
       Tcl_FSRenameFile command is issued at the C level, no such fallbacks occur.  This is  true
       except  for  the last four entries in the filesystem table (lstat, load, getcwd and chdir)
       for which fallbacks do in fact occur at the C level.

       As an example, here is the filesystem lookup table  used  by  the  "vfs"  extension  which
       allows filesystem actions to be implemented in Tcl.
	      static Tcl_Filesystem vfsFilesystem = {
		  "tclvfs",
		  sizeof(Tcl_Filesystem),
		  TCL_FILESYSTEM_VERSION_1,
		  &VfsPathInFilesystem,
		  &VfsDupInternalRep,
		  &VfsFreeInternalRep,
		  /* No internal to normalized, since we don't create any
		   * pure 'internal' Tcl_Obj path representations */
		  NULL,
		  /* No create native rep function, since we don't use it
		   * and don't choose to support uses of 'Tcl_FSNewNativePath' */
		  NULL,
		  /* Normalize path isn't needed - we assume paths only have
		   * one representation */
		  NULL,
		  &VfsFilesystemPathType,
		  &VfsFilesystemSeparator,
		  &VfsStat,
		  &VfsAccess,
		  &VfsOpenFileChannel,
		  &VfsMatchInDirectory,
		  &VfsUtime,
		  /* We choose not to support symbolic links inside our vfs's */
		  NULL,
		  &VfsListVolumes,
		  &VfsFileAttrStrings,
		  &VfsFileAttrsGet,
		  &VfsFileAttrsSet,
		  &VfsCreateDirectory,
		  &VfsRemoveDirectory,
		  &VfsDeleteFile,
		  /* No copy file - fallback will occur at Tcl level */
		  NULL,
		  /* No rename file - fallback will occur at Tcl level */
		  NULL,
		  /* No copy directory - fallback will occur at Tcl level */
		  NULL,
		  /* Core will use stat for lstat */
		  NULL,
		  /* No load - fallback on core implementation */
		  NULL,
		  /* We don't need a getcwd or chdir - fallback on Tcl's versions */
		  NULL,
		  NULL
	      };

       Any  functions  which take path names in Tcl_Obj form take those names in UTF-8 form.  The
       filesystem infrastructure API is designed to support efficient, cached conversion of these
       UTF-8 paths to other native representations.

TYPENAME
       The  typeName  field  contains  a  null-terminated  string that identifies the type of the
       filesystem implemented, e.g.  native or zip or vfs.

STRUCTURE LENGTH
       The structureLength field is generally implemented as sizeof(Tcl_Filesystem), and is there
       to  allow  easier binary backwards compatibility if the size of the structure changes in a
       future Tcl release.

VERSION
       The version field should be set to TCL_FILESYSTEM_VERSION_1.

FILESYSTEM INFRASTRUCTURE
       These fields contain addresses of functions which  are  used  to  associate  a  particular
       filesystem  with a file path, and deal with the internal handling of path representations,
       for example copying and freeing such representations.

PATHINFILESYSTEMPROC
       The pathInFilesystemProc field contains the address of  a  function  which  is  called  to
       determine  whether  a  given path object belongs to this filesystem or not.  Tcl will only
       call the rest of the filesystem functions with a path for which this function has returned
       TCL_OK.	 If the path does not belong, -1 should be returned (the behaviour of Tcl for any
       other return value is not defined).  If TCL_OK is returned, then the  optional  clientDat-
       aPtr  output parameter can be used to return an internal (filesystem specific) representa-
       tion of the path, which will be cached inside the path object, and may be retrieved  effi-
       ciently	by  the  other filesystem functions.  Tcl will simultaneously cache the fact that
       this path belongs to this filesystem.  Such caches are invalidated when filesystem  struc-
       tures are added or removed from Tcl's internal list of known filesystems.

	      typedef int Tcl_FSPathInFilesystemProc(
		Tcl_Obj *pathPtr,
		ClientData *clientDataPtr);

DUPINTERNALREPPROC
       This  function  makes  a  copy of a path's internal representation, and is called when Tcl
       needs to duplicate a path object.  If NULL, Tcl will simply not copy the  internal  repre-
       sentation, which may then need to be regenerated later.

	      typedef ClientData Tcl_FSDupInternalRepProc(
		ClientData clientData);

FREEINTERNALREPPROC
       Free  the  internal  representation.  This must be implemented if internal representations
       need freeing (i.e. if some memory is allocated when an internal representation  is  gener-
       ated), but may otherwise be NULL.

	      typedef void Tcl_FSFreeInternalRepProc(
		ClientData clientData);

INTERNALTONORMALIZEDPROC
       Function  to  convert  internal representation to a normalized path.  Only required if the
       filesystem creates pure path objects with no string/path representation.  The return value
       is a Tcl object whose string representation is the normalized path.

	      typedef Tcl_Obj* Tcl_FSInternalToNormalizedProc(
		ClientData clientData);

CREATEINTERNALREPPROC
       Function to take a path object, and calculate an internal representation for it, and store
       that native representation in the object.  May be NULL if paths have no internal represen-
       tation,	or  if the Tcl_FSPathInFilesystemProc for this filesystem always immediately cre-
       ates an internal representation for paths it accepts.

	      typedef ClientData Tcl_FSCreateInternalRepProc(
		Tcl_Obj *pathPtr);

NORMALIZEPATHPROC
       Function to normalize a path.  Should be implemented for all filesystems  which	can  have
       multiple  string representations for the same path object.  In Tcl, every 'path' must have
       a single unique 'normalized' string representation.  Depending on  the  filesystem,  there
       may  be more than one unnormalized string representation which refers to that path (e.g. a
       relative path, a path with different character case if the filesystem is case insensitive,
       a  path	contain  a  reference to a home directory such as '~', a path containing symbolic
       links, etc).  If the very last component in the path is a symbolic link, it should not  be
       converted  into	the  object  it  points  to (but its case or other aspects should be made
       unique).  All other path components should be converted from  symbolic  links.	This  one
       exception  is  required	to  agree with Tcl's semantics with 'file delete', 'file rename',
       'file copy' operating on symbolic links.  This function may  be	called	with  'nextCheck-
       point'  either at the beginning of the path (i.e. zero), at the end of the path, or at any
       intermediate file separator in the path.  It will never point to any other arbitrary posi-
       tion in the path. In the last of the three valid cases, the implementation can assume that
       the path up to and including the file separator is known and normalized.

	      typedef int Tcl_FSNormalizePathProc(
		Tcl_Interp *interp,
		Tcl_Obj *pathPtr,
		int nextCheckpoint);

FILESYSTEM OPERATIONS
       The fields in this section of the structure  contain  addresses	of  functions  which  are
       called  to  carry  out  the basic filesystem operations.  A filesystem which expects to be
       used with the complete standard Tcl command set must implement all of these.  If  some  of
       them  are  not  implemented,  then  certain  Tcl commands may fail when operating on paths
       within that filesystem.	However, in some instances this may be desirable (for example,	a
       read-only  filesystem should not implement the last four functions, and a filesystem which
       does not support symbolic links need not implement the readlink function,  etc.	 The  Tcl
       core expects filesystems to behave in this way).

FILESYSTEMPATHTYPEPROC
       Function  to  determine the type of a path in this filesystem.  May be NULL, in which case
       no type information will be available to users of the filesystem.  The 'type' is used only
       for  informational  purposes,  and  should be returned as the string representation of the
       Tcl_Obj which is returned.  A typical return value might be "networked", "zip"  or  "ftp".
       The  Tcl_Obj  result  is owned by the filesystem and so Tcl will increment the refCount of
       that object if it wishes to retain a reference to it.

	      typedef Tcl_Obj* Tcl_FSFilesystemPathTypeProc(
		Tcl_Obj *pathPtr);

FILESYSTEMSEPARATORPROC
       Function to return the separator character(s) for this filesystem.  Must  be  implemented,
       otherwise  the file separator command will not function correctly.  The usual return value
       will be a Tcl_Obj containing the string "/".

	      typedef Tcl_Obj* Tcl_FSFilesystemSeparatorProc(
		Tcl_Obj *pathPtr);

STATPROC
       Function to process a Tcl_FSStat() call.  Must be implemented for any reasonable  filesys-
       tem,  since  many Tcl level commands depend crucially upon it (e.g. file atime, file isdi-
       rectory, file size, glob).

	      typedef int Tcl_FSStatProc(
		Tcl_Obj *pathPtr,
		Tcl_StatBuf *statPtr);

       The Tcl_FSStatProc fills the stat structure statPtr with information about  the	specified
       file.   You do not need any access rights to the file to get this information but you need
       search rights to all directories named in the path leading to the file.	The  stat  struc-
       ture  includes  info  regarding device, inode (always 0 on Windows), privilege mode, nlink
       (always 1 on Windows), user id (always 0 on Windows), group id (always 0 on Windows), rdev
       (same  as device on Windows), size, last access time, last modification time, and creation
       time.

       If the file represented by pathPtr exists, the  Tcl_FSStatProc  returns	0  and	the  stat
       structure is filled with data.  Otherwise, -1 is returned, and no stat info is given.

ACCESSPROC
       Function  to  process  a  Tcl_FSAccess()  call.	 Must  be  implemented for any reasonable
       filesystem, since many Tcl level commands depend crucially upon it (e.g. file exists, file
       readable).

	      typedef int Tcl_FSAccessProc(
		Tcl_Obj *pathPtr,
		int mode);

       The  Tcl_FSAccessProc  checks  whether the process would be allowed to read, write or test
       for existence of the file (or other file system object) whose name is pathname.	If  path-
       name  is  a  symbolic  link,  then  permissions of the file referred by this symbolic link
       should be tested.

       On success (all requested permissions granted), zero is returned.  On error (at least  one
       bit  in	mode asked for a permission that is denied, or some other  error occurred), -1 is
       returned.

OPENFILECHANNELPROC
       Function to process a Tcl_FSOpenFileChannel() call.  Must be implemented for  any  reason-
       able  filesystem,  since  any operations which require open or accessing a file's contents
       will use it (e.g. open, encoding, and many Tk commands).

	      typedef Tcl_Channel Tcl_FSOpenFileChannelProc(
		Tcl_Interp *interp,
		Tcl_Obj *pathPtr,
		int mode,
		int permissions);

       The Tcl_FSOpenFileChannelProc opens a file specified by pathPtr and returns a channel han-
       dle  that  can be used to perform input and output on the file.	This API is modeled after
       the fopen procedure of the Unix standard I/O library.  The syntax and meaning of all argu-
       ments  is  similar  to  those given in the Tcl open command when opening a file, where the
       mode argument is a combination of the POSIX flags O_RDONLY, O_WRONLY, etc.   If	an  error
       occurs while opening the channel, the Tcl_FSOpenFileChannelProc returns NULL and records a
       POSIX error code that can be retrieved with Tcl_GetErrno.  In addition, if interp is  non-
       NULL,  the  Tcl_FSOpenFileChannelProc leaves an error message in interp's result after any
       error.

       The newly created channel is not registered in the supplied interpreter; to  register  it,
       use Tcl_RegisterChannel. If one of the standard channels, stdin, stdout or stderr was pre-
       viously closed, the act of creating the new channel also assigns it as a  replacement  for
       the standard channel.

MATCHINDIRECTORYPROC
       Function  to  process  a Tcl_FSMatchInDirectory() call.	If not implemented, then glob and
       recursive copy functionality will be lacking in the filesystem (and this may  impact  com-
       mands like 'encoding names' which use glob functionality internally).

	      typedef int Tcl_FSMatchInDirectoryProc(
		Tcl_Interp* interp,
		Tcl_Obj *result,
		Tcl_Obj *pathPtr,
		CONST char *pattern,
		Tcl_GlobTypeData * types);

       The  function  should  return all files or directories (or other filesystem objects) which
       match the given pattern and accord with the types specification given.  There are two ways
       in  which  this	function  may be called.  If pattern is NULL, then pathPtr is a full path
       specification of a single file or directory which should be checked for existence and cor-
       rect  type.   Otherwise, pathPtr is a directory, the contents of which the function should
       search for files or directories which have the correct type.  In either case, pathPtr  can
       be  assumed  to	be  both  non-NULL and non-empty.  It is not currently documented whether
       pathPtr will have a file separator at its end of not, so code should be flexible  to  both
       possibilities.

       The  return  value  is  a  standard Tcl result indicating whether an error occurred in the
       matching process.  Error messages are placed in interp, but on a TCL_OK result, the inter-
       preter  should  not  be	modified, but rather results should be added to the result object
       given (which can be assumed to be a valid Tcl list).  The matches added to  result  should
       include	any  path  prefix given in pathPtr (this usually means they will be absolute path
       specifications).  Note that if no matches are found, that simply leads to an empty  result
       --- errors are only signaled for actual file or filesystem problems which may occur during
       the matching process.

UTIMEPROC
       Function to process a Tcl_FSUtime() call.  Required to  allow  setting  (not  reading)  of
       times  with 'file mtime', 'file atime' and the open-r/open-w/fcopy implementation of 'file
       copy'.

	      typedef int Tcl_FSUtimeProc(
		Tcl_Obj *pathPtr,
		struct utimbuf *tval);

       The access and modification times of the file specified by pathPtr should  be  changed  to
       the values given in the tval structure.

       The  return  value  is  a  standard Tcl result indicating whether an error occurred in the
       process.

LINKPROC
       Function to process a Tcl_FSLink() call.  Should be implemented	only  if  the  filesystem
       supports links, and may otherwise be NULL.

	      typedef Tcl_Obj* Tcl_FSLinkProc(
		Tcl_Obj *linkNamePtr,
		Tcl_Obj *toPtr,
		int linkAction);

       If  toPtr is NULL, the function is being asked to read the contents of a link.  The result
       is a Tcl_Obj specifying the contents of the link given by linkNamePtr, or NULL if the link
       could  not be read.  The result is owned by the caller, which should call Tcl_DecrRefCount
       when the result is no longer needed.  If toPtr is not NULL, the function should attempt to
       create  a  link.   The  result in this case should be toPtr if the link was successful and
       NULL otherwise.	In this case the result is not owned by the caller. See the documentation
       for Tcl_FSLink for the correct interpretation of the linkAction flags.

LISTVOLUMESPROC
       Function  to  list any filesystem volumes added by this filesystem.  Should be implemented
       only if the filesystem adds volumes at the head of the filesystem, so  that  they  can  be
       returned by 'file volumes'.

	      typedef Tcl_Obj* Tcl_FSListVolumesProc(void);

       The  result  should  be	a  list of volumes added by this filesystem, or NULL (or an empty
       list) if no volumes are provided.  The result object is considered  to  be  owned  by  the
       filesystem  (not by Tcl's core), but should be given a refCount for Tcl.  Tcl will use the
       contents of the list and then decrement that refCount.  This allows filesystems to  choose
       whether	they actually want to retain a 'master list' of volumes or not (if not, they gen-
       erate the list on the fly and pass it to Tcl with a refCount of 1 and  then  forget  about
       the list, if yes, then they simply increment the refCount of their master list and pass it
       to Tcl which will copy the contents and then decrement the count back to where it was).

       Therefore, Tcl considers return values from this proc to be read-only.

FILEATTRSTRINGSPROC
       Function to list all attribute strings which are valid for this filesystem.  If not imple-
       mented the filesystem will not support the file attributes command.  This allows arbitrary
       additional information to be attached to files in the filesystem.  If  it  is  not  imple-
       mented, there is no need to implement the get and set methods.

	      typedef CONST char** Tcl_FSFileAttrStringsProc(
		Tcl_Obj *pathPtr,
		Tcl_Obj** objPtrRef);

       The  called function may either return an array of strings, or may instead return NULL and
       place a Tcl list into the given objPtrRef.  Tcl will take that list  and  first	increment
       its refCount before using it.  On completion of that use, Tcl will decrement its refCount.
       Hence if the list should be disposed of by Tcl when done, it should  have  a  refCount  of
       zero, and if the list should not be disposed of, the filesystem should ensure it retains a
       refCount on the object.

FILEATTRSGETPROC
       Function to process a Tcl_FSFileAttrsGet() call, used by 'file attributes'.

	      typedef int Tcl_FSFileAttrsGetProc(
		Tcl_Interp *interp,
		int index,
		Tcl_Obj *pathPtr,
		Tcl_Obj **objPtrRef);

       Returns a standard Tcl return code.  The attribute value retrieved, which  corresponds  to
       the  index'th  element in the list returned by the Tcl_FSFileAttrStringsProc, is a Tcl_Obj
       placed in objPtrRef (if TCL_OK was returned) and is likely to have  a  refCount	of  zero.
       Either  way we must either store it somewhere (e.g. the Tcl result), or Incr/Decr its ref-
       Count to ensure it is properly freed.

FILEATTRSSETPROC
       Function to process a Tcl_FSFileAttrsSet()  call,  used	by  'file  attributes'.   If  the
       filesystem is read-only, there is no need to implement this.

	      typedef int Tcl_FSFileAttrsSetProc(
		Tcl_Interp *interp,
		int index,
		Tcl_Obj *pathPtr,
		Tcl_Obj *objPtr);

       The  attribute  value  of  the  index'th element in the list returned by the Tcl_FSFileAt-
       trStringsProc should be set to the objPtr given.

CREATEDIRECTORYPROC
       Function to process a Tcl_FSCreateDirectory() call.  Should be implemented unless  the  FS
       is read-only.

	      typedef int Tcl_FSCreateDirectoryProc(
		Tcl_Obj *pathPtr);

       The  return  value  is  a  standard Tcl result indicating whether an error occurred in the
       process.  If successful, a new directory should have been added to the filesystem  in  the
       location specified by pathPtr.

REMOVEDIRECTORYPROC
       Function to process a 'Tcl_FSRemoveDirectory()' call.  Should be implemented unless the FS
       is read-only.

	      typedef int Tcl_FSRemoveDirectoryProc(
		Tcl_Obj *pathPtr,
		int recursive,
		Tcl_Obj **errorPtr);

       The return value is a standard Tcl result indicating whether  an  error	occurred  in  the
       process.   If successful, the directory specified by pathPtr should have been removed from
       the filesystem.	If the recursive flag is given, then  a  non-empty  directory  should  be
       deleted	without  error.   If an error does occur, the name of the file or directory which
       caused the error should be placed in errorPtr.

DELETEFILEPROC
       Function to process a Tcl_FSDeleteFile() call.  Should be implemented  unless  the  FS  is
       read-only.

	      typedef int Tcl_FSDeleteFileProc(
		Tcl_Obj *pathPtr);

       The  return  value  is  a  standard Tcl result indicating whether an error occurred in the
       process.  If successful, the file specified by pathPtr should have been removed	from  the
       filesystem.   Note  that,  if the filesystem supports symbolic links, Tcl will always call
       this function and not Tcl_FSRemoveDirectoryProc when needed to delete them (even  if  they
       are symbolic links to directories).

FILESYSTEM EFFICIENCY
LSTATPROC
       Function to process a Tcl_FSLstat() call.  If not implemented, Tcl will attempt to use the
       statProc defined above instead.	Therefore it need only be implemented if a filesystem can
       differentiate between stat and lstat calls.

	      typedef int Tcl_FSLstatProc(
		Tcl_Obj *pathPtr,
		Tcl_StatBuf *statPtr);

       The behavior of this function is very similar to that of the Tcl_FSStatProc defined above,
       except that if it is applied to a symbolic link, it returns information	about  the  link,
       not about the target file.

COPYFILEPROC
       Function  to  process  a  Tcl_FSCopyFile() call.  If not implemented Tcl will fall back on
       open-r, open-w and fcopy as a copying mechanism.  Therefore it need only be implemented if
       the filesystem can perform that action more efficiently.

	      typedef int Tcl_FSCopyFileProc(
		Tcl_Obj *srcPathPtr,
		Tcl_Obj *destPathPtr);

       The  return  value  is  a  standard Tcl result indicating whether an error occurred in the
       copying process.  Note that, destPathPtr is the name of the file which should  become  the
       copy  of  srcPathPtr.  It  is never the name of a directory into which srcPathPtr could be
       copied (i.e. the function is much simpler than the  Tcl	level  'file  copy'  subcommand).
       Note  that,  if the filesystem supports symbolic links, Tcl will always call this function
       and not Tcl_FSCopyDirectoryProc when needed to copy them (even if they are symbolic  links
       to directories).

RENAMEFILEPROC
       Function  to process a Tcl_FSRenameFile() call.	If not implemented, Tcl will fall back on
       a copy and delete mechanism.  Therefore it need only be implemented if the filesystem  can
       perform that action more efficiently.

	      typedef int Tcl_FSRenameFileProc(
		Tcl_Obj *srcPathPtr,
		Tcl_Obj *destPathPtr);

       The  return  value  is  a  standard Tcl result indicating whether an error occurred in the
       renaming process.

COPYDIRECTORYPROC
       Function to process a Tcl_FSCopyDirectory() call.  If not implemented, Tcl will fall  back
       on  a recursive create-dir, file copy mechanism.  Therefore it need only be implemented if
       the filesystem can perform that action more efficiently.

	      typedef int Tcl_FSCopyDirectoryProc(
		Tcl_Obj *srcPathPtr,
		Tcl_Obj *destPathPtr,
		Tcl_Obj **errorPtr);

       The return value is a standard Tcl result indicating whether  an  error	occurred  in  the
       copying	process.   If an error does occur, the name of the file or directory which caused
       the error should be placed in errorPtr. Note that, destPathPtr is the name of  the  direc-
       tory-name  which  should  become  the  mirror-image of srcPathPtr. It is not the name of a
       directory into which srcPathPtr should be copied (i.e. the function is much  simpler  than
       the Tcl level 'file copy' subcommand).

LOADFILEPROC
       Function  to process a Tcl_FSLoadFile() call.  If not implemented, Tcl will fall back on a
       copy to native-temp followed by a Tcl_FSLoadFile on that  temporary  copy.   Therefore  it
       need  only  be  implemented  if the filesystem can load code directly, or it can be imple-
       mented simply to return	TCL_ERROR  to  disable	load  functionality  in  this  filesystem
       entirely.

	      typedef int Tcl_FSLoadFileProc(
		Tcl_Interp * interp,
		Tcl_Obj *pathPtr,
		Tcl_LoadHandle * handlePtr,
		Tcl_FSUnloadFileProc * unloadProcPtr);

       Returns	a  standard Tcl completion code.  If an error occurs, an error message is left in
       the interp's result.  The function dynamically loads a binary code file into memory.  On a
       successful  load,  the  handlePtr should be filled with a token for the dynamically loaded
       file, and the unloadProcPtr should be filled in with the address of a procedure.  The pro-
       cedure  will  be called with the given Tcl_LoadHandle as its only parameter when Tcl needs
       to unload the file.

UNLOADFILEPROC
       Function to unload a previously successfully loaded file.  If load was  implemented,  then
       this should also be implemented, if there is any cleanup action required.

	      typedef void Tcl_FSUnloadFileProc(
		Tcl_LoadHandle loadHandle);

GETCWDPROC
       Function  to process a Tcl_FSGetCwd() call.  Most filesystems need not implement this.  It
       will usually only be called once, if 'getcwd' is called before 'chdir'.	May be NULL.

	      typedef Tcl_Obj* Tcl_FSGetCwdProc(
		Tcl_Interp *interp);

       If the filesystem supports a native notion of a current	working  directory  (which  might
       perhaps change independent of Tcl), this function should return that cwd as the result, or
       NULL if the current directory could not be determined (e.g. the user does not have  appro-
       priate  permissions  on the cwd directory).  If NULL is returned, an error message is left
       in the interp's result.

CHDIRPROC
       Function to process a Tcl_FSChdir() call.  If filesystems do not implement this,  it  will
       be  emulated by a series of directory access checks.  Otherwise, virtual filesystems which
       do implement it need only respond with a positive return result if the dirName is a valid,
       accessible  directory  in their filesystem.  They need not remember the result, since that
       will be automatically remembered for use by GetCwd.  Real filesystems should carry out the
       correct action (i.e. call the correct system 'chdir' api).

	      typedef int Tcl_FSChdirProc(
		Tcl_Obj *pathPtr);

       The Tcl_FSChdirProc changes the applications current working directory to the value speci-
       fied in pathPtr. The function returns -1 on error or 0 on success.

KEYWORDS
       stat access filesystem vfs

Tcl					       8.4				    Filesystem(3)
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