read_line/[1,2]read_line(-Line)
read_line(+Stream, -Line)
Reads one line of input from Stream, and unifies the
codes with Line. On end of file, Line is unified with
end_of_file.
A valid input text stream, defaults to the current input stream.
end_of_file]
Stream errors (see ref-iou-sfh-est), plus:
permission_errorat_end_of_line/[0,1], ref-iou-cin.