Provided by: tcl9.0-doc_9.0.1+dfsg-1_all 
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,
Tcl_FSTildeExpand - procedures to interact with any filesystem
SYNOPSIS
#include <tcl.h>
int
Tcl_FSRegister(clientData, fsPtr)
int
Tcl_FSUnregister(fsPtr)
void *
Tcl_FSData(fsPtr)
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, 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, index, pathPtr, objPtrRef)
int
Tcl_FSFileAttrsSet(interp, index, pathPtr, 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)
void *
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)
int
Tcl_FSTildeExpand(interp, pathStr, dsPtr)
Tcl_StatBuf *
Tcl_AllocStatBuf()
long long
Tcl_GetAccessTimeFromStat(statPtr)
unsigned
Tcl_GetBlockSizeFromStat(statPtr)
unsigned long long
Tcl_GetBlocksFromStat(statPtr)
long long
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)
long long
Tcl_GetModificationTimeFromStat(statPtr)
unsigned long long
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.
const char *pathStr (in) Pointer to a NUL terminated string representing a file system
path.
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.
int recursive (in) Whether to remove subdirectories and their contents as well.
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.
void *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.
Tcl_Size elements (in) 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.
int index (in) The index of the attribute in question.
Tcl_Obj *objPtr (in) The value to set in the operation.
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_LibraryInitProc **proc1Ptr (out) Filled with the init function for this code.
Tcl_LibraryInitProc **proc2Ptr (out) Filled with the safe-init function for this code.
void **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.
Tcl_Size | int *lenPtr (out) Filled with the number of elements in the split path. May be
(Tcl_Size *)NULL when not used. If it points to a variable
which type is not Tcl_Size, a compiler warning will be
generated. If your extensions is compiled with -DTCL_8_API,
this function will return NULL for paths having more than
INT_MAX elements (which should trigger proper error-
handling), otherwise expect it to crash.
Tcl_Obj *basePtr (in) The base path on to which to join the given elements. May be
NULL.
Tcl_Size 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.
Tcl_DString *dsPtr (out) Pointer to a Tcl_DString to hold an output string result.
________________________________________________________________________________________________________________
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 utf-8 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
“\x1A” (^Z) for all platforms. If you require a “^Z” in code for string comparison, you can use “\x1A”,
which will be safely substituted by the Tcl interpreter into “^Z”. Tcl_FSEvalFile is a simpler version
of Tcl_FSEvalFileEx that always uses the utf-8 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_FSUnloadFile 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 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 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.
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. 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
Tcl_Free 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 macOS, a representation using a fileSpec of FSRef structure would probably be more
efficient). On Windows a full Unicode representation would allow for paths of unlimited length. Currently
the representation is simply a character string 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
Tcl_FSTildeExpand performs tilde substitution on the input path passed via pathStr as described in the
documentation for the file tildeexpand Tcl command. On success, the function returns TCL_OK with the
result of the substitution in dsPtr which must be subsequently freed by the caller. The dsPtr structure
is initialized by the function. No guarantees are made about the form of the returned path such as the
path separators used. The returned result should be passed to other Tcl C API functions such as
Tcl_FSGetNormalizedPath or Tcl_FSGetNativePath if necessary. On error, the function returns TCL_ERROR
with an error message in interp which may be passed as NULL if error messages are not of interest.
PORTABLE STAT RESULT API
Tcl_AllocStatBuf allocates a Tcl_StatBuf on the system heap (which may be deallocated by being passed to
Tcl_Free). 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 {
const char *typeName;
Tcl_Size 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,
void **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 void *Tcl_FSDupInternalRepProc(
void *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(
void *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(
void *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 void *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 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 {
/* 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.
REFERENCE COUNT MANAGEMENT
PUBLIC API CALLS
For all of these functions, pathPtr (including the srcPathPtr and destPathPtr arguments to
Tcl_FSCopyFile, Tcl_FSCopyDirectory, and Tcl_FSRenameFile, the firstPtr and secondPtr arguments to
Tcl_FSEqualPaths, and the linkNamePtr and toPtr arguments to Tcl_FSLink) must not be a zero reference
count value; references may be retained in internal caches even for theoretically read-only operations.
These functions may also manipulate the interpreter result (if they take and are given a non-NULL interp
argument); you must not count on the interpreter result to hold the reference count of any argument value
over these calls and should manage your own references there. However, references held by the arguments
to a Tcl command are suitable for reference count management purposes for the duration of the
implementation of that command.
The errorPtr argument to Tcl_FSCopyDirectory and Tcl_FSRemoveDirectory is, when an object is set into it
at all, set to an object with a non-zero reference count that should be passed to Tcl_DecrRefCount when
no longer needed.
Tcl_FSListVolumes always returns a zero-reference object, much like Tcl_NewObj.
Tcl_FSLink always returns a non-zero-reference object when it is asked to read; you must call
Tcl_DecrRefCount on the object once you no longer need it.
Tcl_FSGetCwd always returns a non-zero-reference object; you must call Tcl_DecrRefCount on the object
once you no longer need it.
Tcl_FSPathSeparator always returns a zero-reference object, much like Tcl_NewObj.
Tcl_FSJoinPath always returns a zero-reference object, much like Tcl_NewObj. Its listObj argument can
have any reference count; it is only read by this function.
Tcl_FSSplitPath always returns a zero-reference object, much like Tcl_NewObj.
Tcl_FSGetNormalizedPath returns an object with a non-zero reference count where Tcl is the owner. You
should increment its reference count if you want to retain it, but do not need to if you are just using
the value immediately.
Tcl_FSJoinToPath always returns a zero-reference object, much like Tcl_NewObj. Its basePtr argument
follows the rules above for pathPtr, as do the values in the objv argument.
Tcl_FSGetTranslatedPath returns a non-zero-reference object (or NULL in the error case); you must call
Tcl_DecrRefCount on the object once you no longer need it.
Tcl_FSNewNativePath always returns a zero-reference object (or NULL), much like Tcl_NewObj.
Tcl_FSFileSystemInfo always returns a zero-reference object (or NULL), much like Tcl_NewObj.
The objPtr and objPtrRef arguments to Tcl_FSFileAttrsGet, Tcl_FSFileAttrsSet and Tcl_FSFileAttrStrings
are conventional Tcl values; the objPtr argument will be read but not retained, and the objPtrRef
argument will have (on success) a zero-reference value written into it (as with Tcl_NewObj).
Tcl_FSFileAttrsGet and Tcl_FSFileAttrsSet may also manipulate the interpreter result.
The resultPtr argument to Tcl_FSMatchInDirectory will not have its reference count manipulated, but it
should have a reference count of no more than 1, and should not be the current interpreter result (as the
function may overwrite that on error).
VIRTUAL FILESYSTEM INTERFACE
For all virtual filesystem implementation functions, any pathPtr arguments should not have their
reference counts manipulated. If they take an interp argument, they may set an error message in that, but
must not manipulate the pathPtr afterwards. Aside from that:
internalToNormalizedProc
This should return a zero-reference count value, as if allocated with Tcl_NewObj.
normalizePathProc
Unlike with other API implementation functions, the pathPtr argument here is guaranteed to be an
unshared object that should be updated. Its reference count should not be modified.
filesystemPathTypeProc
The return value (if non-NULL) either has a reference count of zero or needs to be maintained (on
a per-thread basis) by the filesystem. Tcl will increment the reference count of the value if it
wishes to retain it.
filesystemSeparatorProc
The return value should be a value with reference count of zero.
matchInDirectoryProc
The resultPtr argument should be assumed to hold a list that can be appended to (i.e., that has a
reference count no greater than 1). No reference to it should be retained.
linkProc
If toPtr is NULL, this should return a value with reference count 1 that has just been allocated
and passed to Tcl_IncrRefCount. If toPtr is not NULL, it should be returned on success.
listVolumesProc
The result value should be a list (if non-NULL); it will have its reference count decremented once
(with Tcl_DecrRefCount) by Tcl once done.
fileAttrStringsProc
If the result is NULL, the objPtrRef should have a list value written to it; that list will have
its reference count both incremented (with Tcl_IncrRefCount) and decremented (with
Tcl_DecrRefCount).
fileAttrsGetProc
The objPtrRef argument should have (on non-error return) a zero reference count value written to
it (allocated as if with Tcl_NewObj).
fileAttrsSetProc
The objPtr argument should either just be read or its reference count incremented to retain it.
removeDirectoryProc
If an error is being reported, the problem filename reported via errorPtr should be newly
allocated (as if with Tcl_NewObj) and have a reference count of 1 (i.e., have been passed to
Tcl_IncrRefCount).
copyDirectoryProc
If an error is being reported, the problem filename reported via errorPtr should be newly
allocated (as if with Tcl_NewObj) and have a reference count of 1 (i.e., have been passed to
Tcl_IncrRefCount).
getCwdProc
The result will be passed to Tcl_DecrRefCount by the implementation of Tcl_FSGetCwd after it has
been normalized.
SEE ALSO
cd(3tcl), file(3tcl), filename(3tcl), load(3tcl), open(3tcl), pwd(3tcl), source(3tcl), unload(3tcl)
KEYWORDS
stat, access, filesystem, vfs, virtual filesystem
Tcl 8.4 Filesystem(3tcl)