Filesystem(3) Tcl Library Procedures Filesystem(3)

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NAME

Tcl_FSRegister, Tcl_FSUnregister, Tcl_FSData, Tcl_FSMountsChanged,
Tcl_FSGetFileSystemForPath, Tcl_FSGetPathType, Tcl_FSCopyFile,
Tcl_FSCopyDirectory, Tcl_FSCreateDirectory, Tcl_FSDeleteFile,
Tcl_FSRemoveDirectory, Tcl_FSRenameFile, Tcl_FSListVolumes,
Tcl_FSEvalFile, Tcl_FSEvalFileEx, Tcl_FSLoadFile, Tcl_FSUnloadFile,
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_FSConvertToPathType, Tcl_FSGetInternalRep,
Tcl_FSGetTranslatedPath, Tcl_FSGetTranslatedStringPath,
Tcl_FSNewNativePath, Tcl_FSGetNativePath, Tcl_FSFileSystemInfo,
Tcl_GetAccessTimeFromStat, Tcl_GetBlockSizeFromStat,
Tcl_GetBlocksFromStat, Tcl_GetChangeTimeFromStat,
Tcl_GetDeviceTypeFromStat, Tcl_GetFSDeviceFromStat,
Tcl_GetFSInodeFromStat, Tcl_GetGroupIdFromStat,
Tcl_GetLinkCountFromStat, Tcl_GetModeFromStat,
Tcl_GetModificationTimeFromStat, Tcl_GetSizeFromStat,
Tcl_GetUserIdFromStat, 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)

const Tcl_Filesystem *
Tcl_FSGetFileSystemForPath(pathPtr)

Tcl_PathType
Tcl_FSGetPathType(pathPtr)

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_FSEvalFileEx(interp, pathPtr, encodingName)

int
Tcl_FSEvalFile(interp, pathPtr)

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

int |
Tcl_FSUnloadFile(interp, loadHandle) |

int
Tcl_FSMatchInDirectory(interp, resultPtr, 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 *const *
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 void *
Tcl_FSGetNativePath(pathPtr)

Tcl_Obj *
Tcl_FSFileSystemInfo(pathPtr)

Tcl_StatBuf *
Tcl_AllocStatBuf()

Tcl_WideInt |
Tcl_GetAccessTimeFromStat(statPtr) |

unsigned |
Tcl_GetBlockSizeFromStat(statPtr) |

Tcl_WideUInt |
Tcl_GetBlocksFromStat(statPtr) |

Tcl_WideInt |
Tcl_GetChangeTimeFromStat(statPtr) |

int |
Tcl_GetDeviceTypeFromStat(statPtr) |

unsigned |
Tcl_GetFSDeviceFromStat(statPtr) |

unsigned |
Tcl_GetFSInodeFromStat(statPtr) |

int |
Tcl_GetGroupIdFromStat(statPtr) |

int |
Tcl_GetLinkCountFromStat(statPtr) |

unsigned |
Tcl_GetModeFromStat(statPtr) |

Tcl_WideInt |
Tcl_GetModificationTimeFromStat(statPtr) |

Tcl_WideUInt |
Tcl_GetSizeFromStat(statPtr) |

int |
Tcl_GetUserIdFromStat(statPtr) |

ARGUMENTS

const Tcl_Filesystem *fsPtr (in) Points to a structure
containing the addresses
of procedures that can be
called to perform the
various filesystem
operations.

Tcl_Obj *pathPtr (in) The path represented by
this value is used for
the operation in
question. If the value
does not already have an
internal path
representation, it will
be converted 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 *encodingName (in) The encoding of the data
stored in the file
identified by pathPtr and
to be evaluated.

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

Tcl_GlobTypeData *types (in) Only files or directories
matching the type
descriptions contained in
this structure will be
returned. 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 value to create.

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

Tcl_Obj *secondPtr (in) The second of two path
values to compare. The
value 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 a value
containing the name of
the file which caused an
error in the various
copy/rename operations.

Tcl_Obj **objPtrRef (out) Filled with a value
containing the result of
the operation.

Tcl_Obj *resultPtr (out) Preallocated value in
which to store (using
Tcl_ListObjAppendElement)
the list of files or
directories which are
successfully matched.

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 checking 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.

Tcl_LoadHandle *loadHandlePtr (out) Filled with an abstract
token representing the
loaded file.

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

Tcl_LoadHandle loadHandle (in) Handle to the loaded
library to be unloaded.

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.

Tcl_Obj *linkNamePtr (in) The name of the link to
be created or read.

Tcl_Obj *toPtr (in) What the link called
linkNamePtr should be
linked to, or NULL if the
symbolic link specified
by linkNamePtr is to be
read.

int linkAction (in) OR-ed combination of
flags indicating what
kind of link should be
created (will be ignored
if toPtr is NULL). Valid
bits to set are
TCL_CREATE_SYMBOLIC_LINK
and TCL_CREATE_HARD_LINK.
When both flags are set
and the underlying
filesystem can do either,
symbolic links are
preferred.
____________________________________________________________________________

DESCRIPTION

There are several reasons for calling the Tcl_FS API functions
(e.g. Tcl_FSAccess and Tcl_FSStat) 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 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
conversions 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 functions are "virtual
filesystem aware". Any virtual filesystem (VFS for short) 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 (FS for short) 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 VFSes 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 archive). 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 is
actually declared to be, allowing the same code to be used both on
systems with and systems without support for files larger than 2GB in
size.

The Tcl_FS API is Tcl_Obj-ified 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 values with a reference count 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 value, and so one must not assume that
after any of these calls return, the value still has a reference
count of zero - it may have been incremented) or in a direct
segmentation fault (or other memory access error) due to the value
being freed part way through the complex value manipulation required
to ensure that the path is fully normalized and absolute for
filesystem determination. The practical lesson to learn from this is
that

Tcl_Obj *path = Tcl_NewStringObj(...);
Tcl_FSWhatever(path);
Tcl_DecrRefCount(path);

is wrong, and may cause memory errors. The path must have its
reference count incremented before passing it in, or decrementing it.
For this reason, values with a reference count of zero are considered
not to be valid filesystem paths and calling any Tcl_FS API function
with such a value will result in no action being taken.

FS API FUNCTIONS

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_FSGetFileSystemForPath) then that
filesystem's "copy file" function is called (if it is non-NULL).
Otherwise the function returns -1 and sets the errno global C
variable 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 the errno global C variable 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 the errno global C variable 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 reference count of 0).

Tcl_FSEvalFileEx reads the file given by pathPtr using the encoding
identified by encodingName and evaluates its contents as a Tcl
script. It returns the same information as Tcl_EvalObjEx. If
encodingName is NULL, the system encoding is used for reading the
file contents. If the file could not be read then a Tcl error is
returned to describe why the file could not 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_FSEvalFile
is a simpler version of Tcl_FSEvalFileEx that always uses the system
encoding when reading the file.

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. |

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

The token provided via the variable indicated by loadHandlePtr may be |
used with Tcl_FindSymbol.

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 globbing. Error messages are placed in interp (unless
interp is NULL, which is allowed), 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 asking only for directories to be
returned. A special case of being called with a NULL pattern
indicates that the path needs to be checked only for the correct
type.

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

If the toPtr is NULL, a "read link" 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'ed combination of TCL_CREATE_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 successfully created, the return value should be toPtr (which
is therefore already owned by the caller). If unsuccessful, NULL is
returned.

Tcl_FSLstat fills the Tcl_StatBuf 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 Tcl_StatBuf
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 last metadata change time. See PORTABLE STAT RESULT API for a
description of how to write portable code to allocate and access the
Tcl_StatBuf structure.

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

Tcl_FSUtime replaces the library version of utime.

This returns 0 on success and -1 on error (as per the 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 a value was placed in objPtrRef, which
will only be temporarily 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 reference count
before using it. On completion of that use, Tcl will decrement its
reference count. Hence if the list should be disposed of by Tcl when
done, it should have a reference count of zero, and if the list
should not be disposed of, the filesystem should ensure it retains a
reference count to the value.

Tcl_FSAccess checks whether the process would be allowed to read,
write or test for existence of the file (or other filesystem 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 Tcl_StatBuf 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 Tcl_StatBuf
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 last metadata change time. See PORTABLE STAT RESULT API for a
description of how to write portable code to allocate and access the
Tcl_StatBuf structure.

If path exists, Tcl_FSStat returns 0 and the stat structure is filled
with data. Otherwise, -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. 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, which happens
when the current working directory is not in the native filesystem.

The result is a pointer to a Tcl_Obj specifying the current
directory, or NULL if the current directory could not be determined.
If NULL is returned, an error message is left in the interp's result.

The result already has its reference count incremented for the
caller. When it is no longer needed, that reference count 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
Tcl_FSGetCwd.

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 must be a valid list
(which is allowed to have a reference count of zero), and returns the
path value given by considering the first elements elements as valid
path segments (each path segment may be a complete path, a partial
path or just a single possible directory or file name). If any path
segment is actually an absolute path, then all prior path segments
are discarded. If elements is less than 0, we use the entire list.

It is possible that the returned value is actually an element of the
given list, so the caller should be careful to increment the
reference count of the result before freeing the list.

The returned value, typically with a reference count of zero (but it
could be shared under some conditions), contains the joined path. The
caller must add a reference count to the value before using it. In
particular, the returned value could be an element of the given list,
so freeing the list might free the value prematurely if no reference
count has been taken. If the number of elements is zero, then the
returned value will be an empty-string Tcl_Obj.

Tcl_FSSplitPath takes the given Tcl_Obj, which should be a valid
path, and returns a Tcl list value containing each segment of that
path as an element. It returns a list value with a reference count
of zero. If the passed in lenPtr is non-NULL, the variable it points
to will be updated to contain 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 identifier for the file.

It returns the normalized path value, owned by Tcl, or NULL if the
path was invalid or could otherwise not be successfully converted.
Extraction of absolute, normalized 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. The return
value is owned by Tcl and has a lifetime equivalent to that of the
pathPtr passed in (unless that is a relative path, in which case the
normalized path value may be freed any time the cwd changes) - the
caller can of course increment the reference count if it wishes to
maintain a copy for longer.

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

Returns a value, typically with reference count of zero (but it could
be shared under some conditions), containing the joined path. The
caller must add a reference count to the value before using it. If
any of the values passed into this function (pathPtr or path
elements) have a reference count of zero, they will be freed when
this function returns.

Tcl_FSConvertToPathType tries to convert the given Tcl_Obj to a valid
Tcl path type, taking account of the fact that the cwd may have
changed even if this value is already supposedly 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 value is a valid path in one of
the current filesystems), 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 value, in the given filesystem. If the path value 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 value is a valid path), then it
is returned. Otherwise 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). The value returned
is owned by the caller, which must store it or call Tcl_DecrRefCount
to ensure memory is freed. This function is of little practical use,
and Tcl_FSGetNormalizedPath or Tcl_FSGetNativePath are usually better
functions to use for most purposes.

Tcl_FSGetTranslatedStringPath does the same as
Tcl_FSGetTranslatedPath, but returns a character string or NULL. The
string returned is dynamically allocated and owned by the caller,
which must store it or call ckfree to ensure it is freed. Again,
Tcl_FSGetNormalizedPath or Tcl_FSGetNativePath are usually better
functions to use for most purposes.

Tcl_FSNewNativePath performs something like the 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 value type.

The resulting value is a pure "path" value, which will only receive a
UTF-8 string representation if that is required by some Tcl code.

Tcl_FSGetNativePath is for use by the Win/Unix 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. It may be desirable in the future to
have non-string-based native representations (for example, on MacOSX,
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 which may contain either the relative path
or a complete, absolute normalized path in the native encoding
(complex conditions dictate which of these will be provided, so
neither can be relied upon, unless the path is known to be absolute).
If you need a native path which must be absolute, then you should ask
for the native version of a normalized path. If for some reason a
non-absolute, non-normalized version of the path is needed, that must
be constructed separately (e.g. using Tcl_FSGetTranslatedPath).

The native representation is cached so that repeated calls to this
function will not require additional conversions. The return value is
owned by Tcl and has a lifetime equivalent to that of the pathPtr
passed in (unless that is a relative path, in which case the native
representation may be freed any time the cwd changes).

Tcl_FSFileSystemInfo returns a list of two elements. The first
element is the name of the filesystem (e.g. "native", "vfs", "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 categorization of files.

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

Tcl_FSGetFileSystemForPath returns 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

PORTABLE STAT RESULT API

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.

The portable fields of a Tcl_StatBuf may be read using the following |
functions, each of which returns the value of the corresponding field |
listed in the table below. Note that on some platforms there may be |
other fields in the Tcl_StatBuf as it is an alias for a suitable |
system structure, but only the portable ones are made available here. |
See your system documentation for a full description of these fields. |

Access Function Field |
Tcl_GetFSDeviceFromStat st_dev |
Tcl_GetFSInodeFromStat st_ino |
Tcl_GetModeFromStat st_mode |
Tcl_GetLinkCountFromStat st_nlink |
Tcl_GetUserIdFromStat st_uid |
Tcl_GetGroupIdFromStat st_gid |
Tcl_GetDeviceTypeFromStat st_rdev |
Tcl_GetAccessTimeFromStat st_atime |
Tcl_GetModificationTimeFromStat st_mtime |
Tcl_GetChangeTimeFromStat st_ctime |
Tcl_GetSizeFromStat st_size |
Tcl_GetBlocksFromStat st_blocks |
Tcl_GetBlockSizeFromStat st_blksize |

THE VIRTUAL FILESYSTEM API

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 filesystems, 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
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 perform 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_FSRenameFileProc
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.

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.

EXAMPLE FILESYSTEM DEFINITION

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; use the core fallback mechanism */
NULL,
/* No rename file; use the core fallback mechanism */
NULL,
/* No copy directory; use the core fallback mechanism */
NULL,
/* Core will use stat for lstat */
NULL,
/* No load; use the core fallback mechanism */
NULL,
/* We don't need a getcwd or chdir; the core's own
* internal value is suitable */
NULL,
NULL
};

FILESYSTEM INFRASTRUCTURE

These fields contain basic information about the filesystem structure
and 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.

TYPENAME

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

PATHINFILESYSTEMPROC

The pathInFilesystemProc field contains the address of a function
which is called to determine whether a given path value 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 behavior of
Tcl for any other return value is not defined). If TCL_OK is
returned, then the optional clientDataPtr output parameter can be
used to return an internal (filesystem specific) representation of
the path, which will be cached inside the path value, and may be
retrieved efficiently by the other filesystem functions. Tcl will
simultaneously cache the fact that this path belongs to this
filesystem. Such caches are invalidated when filesystem structures
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 value. If NULL, Tcl will
simply not copy the internal representation, 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 generated), 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 values with no
string/path representation. The return value is a Tcl value whose
string representation is the normalized path.

typedef Tcl_Obj *Tcl_FSInternalToNormalizedProc(
ClientData clientData);

CREATEINTERNALREPPROC

Function to take a path value, and calculate an internal
representation for it, and store that native representation in the
value. May be NULL if paths have no internal representation, or if
the Tcl_FSPathInFilesystemProc for this filesystem always immediately
creates 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 value. 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 value 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 nextCheckpoint 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
position 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 reference count of that value 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.
This need only be implemented if the filesystem wishes to use a
different separator than the standard string "/". Amongst other
uses, it is returned by the file separator command. The return value
should be a value with reference count of zero.

typedef Tcl_Obj *Tcl_FSFilesystemSeparatorProc(
Tcl_Obj *pathPtr);

STATPROC

Function to process a Tcl_FSStat call. Must be implemented for any
reasonable filesystem, since many Tcl level commands depend crucially
upon it (e.g. file atime, file isdirectory, 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 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 last
metadata change 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 filesystem
object) whose name is in pathPtr. If the pathname refers to a
symbolic link, then the 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 reasonable 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 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,
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 must not be registered in the supplied
interpreter by a Tcl_FSOpenFileChannelProc; that task is up to the
caller of Tcl_FSOpenFileChannel (if necessary). 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.

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 commands like encoding
names which use glob functionality internally).

typedef int Tcl_FSMatchInDirectoryProc(
Tcl_Interp *interp,
Tcl_Obj *resultPtr,
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 correct 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, unless interp in NULL in which case no error message need be
generated; on a TCL_OK result, results should be added to the
resultPtr value given (which can be assumed to be a valid unshared
Tcl list). The matches added to resultPtr 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.

The Tcl_GlobTypeData structure passed in the types parameter contains
the following fields:

typedef struct Tcl_GlobTypeData {
/* Corresponds to bcdpfls as in 'find -t' */
int type;
/* Corresponds to file permissions */
int perm;
/* Acceptable mac type */
Tcl_Obj *macType;
/* Acceptable mac creator */
Tcl_Obj *macCreator;
} Tcl_GlobTypeData;

There are two specific cases which it is important to handle
correctly, both when types is non-NULL. The two cases are when
types->types & TCL_GLOB_TYPE_DIR or types->types &
TCL_GLOB_TYPE_MOUNT are true (and in particular when the other flags
are false). In the first of these cases, the function must list the
contained directories. Tcl uses this to implement recursive globbing,
so it is critical that filesystems implement directory matching
correctly. In the second of these cases, with TCL_GLOB_TYPE_MOUNT,
the filesystem must list the mount points which lie within the given
pathPtr (and in this case, pathPtr need not lie within the same
filesystem - different to all other cases in which this function is
called). Support for this is critical if Tcl is to have seamless
transitions between from one filesystem to another.

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 should be 0 on success and -1 on an error, as with
the system utime.

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 (and should therefore have its ref
count incremented before being returned). Any callers should call
Tcl_DecrRefCount on this result when it 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
(i.e. no reference count manipulations on either end are needed). 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 value
is considered to be owned by the filesystem (not by Tcl's core), but
should be given a reference count for Tcl. Tcl will use the contents
of the list and then decrement that reference count. This allows
filesystems to choose whether they actually want to retain a "global
list" of volumes or not (if not, they generate the list on the fly
and pass it to Tcl with a reference count of 1 and then forget about
the list, if yes, then they simply increment the reference count of
their global 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 implemented 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 implemented,
there is no need to implement the get and set methods.

typedef const char *const *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 reference count
before using it. On completion of that use, Tcl will decrement its
reference count. Hence if the list should be disposed of by Tcl when
done, it should have a reference count of zero, and if the list
should not be disposed of, the filesystem should ensure it returns a
value with a reference count of at least one.

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 reference count of zero.
Either way we must either store it somewhere (e.g. the Tcl result),
or Incr/Decr its reference 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_FSFileAttrStringsProc 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 this flag is not given, then and the directory is
non-empty a POSIX "EEXIST" error should be signaled. 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

These functions need not be implemented for a particular filesystem
because the core has a fallback implementation available. See each
individual description for the consequences of leaving the field
NULL.

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 copyDirectoryProc when
needed to copy them (even if they are symbolic links to directories).
Finally, if the filesystem determines it cannot support the file copy
action, calling Tcl_SetErrno(EXDEV) and returning a non-TCL_OK result
will tell Tcl to use its standard fallback mechanisms.

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. If the filesystem determines it
cannot support the file rename action, calling Tcl_SetErrno(EXDEV)
and returning a non-TCL_OK result will tell Tcl to use its standard
fallback mechanisms.

COPYDIRECTORYPROC

Function to process a Tcl_FSCopyDirectory call. If not implemented,
Tcl will fall back on a recursive file mkdir, 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 directory-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).
Finally, if the filesystem determines it cannot support the directory
copy action, calling Tcl_SetErrno(EXDEV) and returning a non-TCL_OK
result will tell Tcl to use its standard fallback mechanisms.

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 implemented 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 unload procedure will be called with the given
Tcl_LoadHandle as its only parameter when Tcl needs to unload the
file. For example, for the native filesystem, the Tcl_LoadHandle
returned is currently a token which can be used in the private
TclpFindSymbol to access functions in the new code. Each filesystem
is free to define the Tcl_LoadHandle as it requires. Finally, if the
filesystem determines it cannot support the file load action, calling
Tcl_SetErrno(EXDEV) and returning a non-TCL_OK result will tell Tcl
to use its standard fallback mechanisms.

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
appropriate 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 pathPtr is a valid,
accessible directory in their filesystem. They need not remember the
result, since that will be automatically remembered for use by
Tcl_FSGetCwd. 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 specified in pathPtr. The function returns -1
on error or 0 on success.

SEE ALSO

cd(n), file(n), filename(n), load(n), open(n), pwd(n), source(n),
unload(n)

KEYWORDS

stat, access, filesystem, vfs, virtual filesystem

Tcl 8.4 Filesystem(3)