       lgets fileId ?varName?
              Reads  the  next  Tcl  list  from the file given by
              fileId and discards the terminating newline charac-
              ter.   This  command differs from the gets command,
              in that it reads Tcl lists rather than  lines.   If
              the list contains a newline, then that newline will
              be returned as part of the result.  Only a  newline
              not quoted as part of the list indicates the end of
              the list.  There is no  corresponding  command  for
              outputting lists, as puts will do this correctly.

              If varName is specified, then the line is placed in
              the variable by that name and the return value is a
              count of the number of characters read (not includ-
              ing the newline).   If  the  end  of  the  file  is
              reached  before  reading  any characters then -1 is
              returned and varName is set to an empty string.  If
              varName is specified and an error occurs, what ever
              data was read will be  returned  in  the  variable,
              however  the  resulting  string  may not be a valid
              list.

              If varName is not specified then the  return  value
              will  be  the line (minus the newline character) or
              an empty string if the end of the file  is  reached
              before  reading  any  characters.   An empty string
              will also be returned if a line contains no charac-
              ters except the newline, so eof may have to be used
              to determine what really happened.

              If lgets is used on a non-blocking  file,  blocking
              will be temporarily enabled for the duration of the
              lgets command.  This is  required  by  the  current
              implementation  of  the  underlying Tcl I/O system.
              In most cases, this will not cause any problems, as
              the  process  writing  the  file  should be writing
              entire lists in one  write  operation.    The  only
              difficulty  that might arise is if non-blocking I/O
              was being used to keep two processes from deadlock-
              ing while exchanging large amounts of data.

              This command is provided by Extended Tcl.
