title: stty hupcl ixon ixoff
body: <p>I'm seeing <code>stty, not a typewritter</code> messages on hpux (despite an interactive terminal check?), and am guessing that these are due to the  stty lines in my .kshrc file:</p>
  
  <pre><code>case $- in
  *i* )
      stty hupcl ixon ixoff
      stty erase '^?' kill '^U' intr '^C' eof '^D' susp '^Z'
  ;;
  esac
  </code></pre>
  
  <p>Two questions:</p>
  
  <p>1) 
  I know why the erase line is there, since backspace doesn't work without it.  These .kshrc lines I've inherited, but don't know what they do.</p>
  
  <p>Anybody know the point of the hupcl ixon ixoff lines?  The stty man page isn't particularly enlightening:</p>
  
  <pre><code>hupcl (-hupcl)           Hang up (do not hang up) modem connection on
                           last close.
  
  ixon (-ixon)             Enable (disable) START/STOP output control.
                           Output is stopped by sending an ASCII DC3 and
                           started by sending an ASCII DC1.
  
  ixoff (-ixoff)           Request that the system send (not send)
                           START/STOP characters when the input queue is
                           nearly empty/full.
  </code></pre>
  
  <p>2) Is there a different way to check for interactive terminals.  I had tty -s ; if [ $? ] before but that also appears to be noisy on hpux.</p>