       ftruncate [-fileid] file newsize
              Truncate a file to have a length of at most newsize
              bytes.

              If the option -fileid is specified, file is an open
              file identifier, otherwise it is a file path.

              This command is not available on all systems if the
              underlying operating system support is  not  avail-
              able.   The  command infox have_truncate will indi-
              cate if this command is available.   On  some  sys-
              tems,  the  -fileid option is not available,  check
              the result of infox have_ftruncate to see if it can
              be used.

              This command is provided by Extended Tcl.
