This command is part of the TclX package.

fstat fileid
fstat fileid item
fstat fileid stat arrayvar

Get the metadata for an open file given by handle fileid (compare with file stat and file lstat). If no other arguments are given, return the information in a keyed list. If item is given, return the value of that item only. If “stat arrayvar” is given, store the information in the named array.