Filesystem(3) Tcl Library Procedures Filesystem(3)______________________________________________________________________________NAME
Tcl_FSRegister, Tcl_FSUnregister, Tcl_FSData, Tcl_FSMountsChanged,
Tcl_FSGetFileSystemForPath, Tcl_FSGetPathType, Tcl_FSCopyFile,
Tcl_FSCopyDirectory, Tcl_FSCreateDirectory, Tcl_FSDeleteFile, Tcl_FSRe‐
moveDirectory, Tcl_FSRenameFile, Tcl_FSListVolumes, Tcl_FSEvalFile,
Tcl_FSEvalFileEx, Tcl_FSLoadFile, Tcl_FSUnloadFile, Tcl_FSMatchInDirec‐
tory, 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_FSGetNormalized‐
Path, Tcl_FSJoinToPath, Tcl_FSConvertToPathType, Tcl_FSGetInternalRep,
Tcl_FSGetTranslatedPath, Tcl_FSGetTranslatedStringPath, Tcl_FSNewNa‐
tivePath, Tcl_FSGetNativePath, Tcl_FSFileSystemInfo, Tcl_GetAccessTime‐
FromStat, Tcl_GetBlockSizeFromStat, Tcl_GetBlocksFromStat,
Tcl_GetChangeTimeFromStat, Tcl_GetDeviceTypeFromStat, Tcl_GetFSDevice‐
FromStat, Tcl_GetFSInodeFromStat, Tcl_GetGroupIdFromStat,
Tcl_GetLinkCountFromStat, Tcl_GetModeFromStat, Tcl_GetModificationTime‐
FromStat, 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 con‐
taining the addresses of
procedures that can be
called to perform the vari‐
ous 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 rep‐
resentation, 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 file‐
name for a copy or rename
operation.
const char *encodingName (in) The encoding of the data
stored in the file identi‐
fied 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 descrip‐
tions 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 val‐
ues to compare. The value
may be converted to path
type.
Tcl_Obj *secondPtr (in) The second of two path val‐
ues 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 con‐
taining the name of the
file which caused an error
in the various copy/rename
operations.
Tcl_Obj **objPtrRef (out) Filled with a value con‐
taining the result of the
operation.
Tcl_Obj *resultPtr (out) Pre-allocated value in
which to store (using
Tcl_ListObjAppendElement)
the list of files or direc‐
tories which are success‐
fully 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 exe‐
cute permissions, respec‐
tively. 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 ta‐
ble
const char *sym2 (in) Name of a procedure to look
up in the file's symbol ta‐
ble
Tcl_PackageInitProc **proc1Ptr (out) Filled with the init func‐
tion 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_SYM‐
BOLIC_LINK and TCL_CRE‐
ATE_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 func‐
tion 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 there‐
fore 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 functional‐
ity 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 ref‐
erence count of zero to any of these functions. If such calls were han‐
dled, 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 incre‐
mented) 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 filesys‐
tem'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). Oth‐
erwise 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 call‐
ing 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 src‐
PathPtr 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 vol‐
umes” 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. Tcl_FSUnload‐ │
File reverses the operation, asking for the library indicated by the │
loadHandle to be removed from the process. Note that, unlike with the │
unload command, this does not give the library any opportunity to clean │
up.
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 direc‐
tory for all files which match a given pattern. The appropriate func‐
tion 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 ORed
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 documenta‐
tion). 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 path‐
Ptr 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 permis‐
sions 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 stan‐
dard 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_FSOpenFileChan‐
nel leaves an error message in interp's result after any error.
The newly created channel is not registered in the supplied inter‐
preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
dard 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 decre‐
mented. 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 normal‐
ized 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 dis‐
carded. 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 par‐
ticular, 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. Extrac‐
tion 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 call‐
er 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_FSGetNor‐
malizedPath 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 dynami‐
cally 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 pur‐
poses.
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*) representa‐
tion 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 repre‐
sentation 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 com‐
plete, absolute normalized path in the native encoding (complex condi‐
tions 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 cate‐
gorization of files.
A valid list value is returned, unless the path value is not recog‐
nized, 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 gen‐
erally occurs through the functions listed above.
The Tcl_Filesystem structures are manipulated using the following meth‐
ods.
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 sim‐
ple data elements, all entries contain addresses of functions called by
the generic filesystem layer to perform the complete range of filesys‐
tem related actions.
The many functions in this structure are broken down into three cate‐
gories: infrastructure functions (almost all of which must be imple‐
mented), 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_FSCopy‐
FileProc followed by Tcl_FSDeleteFileProc, and if Tcl_FSCopyFileProc is
not implemented there is a further fallback). However, if a Tcl_FSRe‐
nameFileProc 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 rep‐
resentations.
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 representa‐
tions.
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 func‐
tions 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 inter‐
nal (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 sim‐
ply 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 represen‐
tation 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_FSPathIn‐
FilesystemProc for this filesystem always immediately creates an inter‐
nal 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 rep‐
resentation. 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 sym‐
bolic links. This one exception is required to agree with Tcl's seman‐
tics 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 func‐
tions which are called to carry out the basic filesystem operations. A
filesystem which expects to be used with the complete standard Tcl com‐
mand set must implement all of these. If some of them are not imple‐
mented, then certain Tcl commands may fail when operating on paths
within that filesystem. However, in some instances this may be desir‐
able (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 differ‐
ent 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 rea‐
sonable 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 simi‐
lar 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 inter‐
preter 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 filesys‐
tem 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 cor‐
rect 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 incre‐
mented 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 filesys‐
tems to choose whether they actually want to retain a “master 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 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 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 sym‐
bolic 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. There‐
fore 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_SetEr‐
rno(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 effi‐
ciently.
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 can‐
not support the file rename action, calling Tcl_SetErrno(EXDEV) and
returning a non-TCL_OK result will tell Tcl to use its standard fall‐
back mechanisms.
COPYDIRECTORYPROC
Function to process a Tcl_FSCopyDirectory call. If not implemented, Tcl
will fall back on a recursive file mkdir, file copy mechanism. There‐
fore 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 func‐
tion 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 direc‐
tory (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 per‐
missions 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. Oth‐
erwise, 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 ALSOcd(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)
