int Tcl_Access(path, mode)
int Tcl_Stat(path, statPtr)
As of Tcl 8.4, the object-based APIs Tcl_FSAccess and Tcl_FSStat should be used in preference to Tcl_Access and Tcl_Stat, wherever possible.
There are two reasons for calling Tcl_Access and Tcl_Stat rather than calling system level functions access and stat directly. First, the Windows implementation of both functions fixes some bugs in the system level calls. Second, both Tcl_Access and Tcl_Stat (as well as Tcl_OpenFileChannelProc) hook into a linked list of functions. This allows the possibility to reroute file access to alternative media or access methods.
Tcl_Access checks whether the process would be allowed to read, write or test for existence of the file (or other file system object) whose name is pathname. If 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_Stat fills the stat structure statPtr with information about the specified file. You do not need any access rights to the file to get this information but you need search rights to all directories named in the path leading to the file. The stat structure includes info regarding device, inode (always 0 on Windows), privilege mode, nlink (always 1 on Windows), user id (always 0 on Windows), group id (always 0 on Windows), rdev (same as device on Windows), size, last access time, last modification time, and creation time.
If path exists, Tcl_Stat returns 0 and the stat structure is filled with data. Otherwise, -1 is returned, and no stat info is given.