shl(1)                 (User Environment Utilities)                  shl(1)


   NAME
         shl - shell layer manager

   SYNOPSIS
         shl

   DESCRIPTION
         shl allows a user to interact with more than one shell from a single
         terminal.  The user controls these shells, known as layers, using the
         commands described below.

         The current layer is the layer which can receive input from the
         keyboard.  Other layers attempting to read from the keyboard are
         blocked.  Output from multiple layers is multiplexed onto the
         terminal.  To have the output of a layer blocked when it is not
         current, the stty option loblk may be set within the layer.

         The stty character swtch (set to ^Z if NUL) is used to switch control
         to shl from a layer.  shl has its own prompt, >>>, to help
         distinguish it from a layer.

         A layer is a shell which has been bound to a virtual tty device
         (/dev/sxt???).  The virtual device can be manipulated like a real tty
         device using stty(1) and ioctl(2).  Each layer has its own process
         group id.

      Definitions
         A name is a sequence of characters delimited by a blank, tab or new-
         line.  Only the first eight characters are significant.  The names
         (1) through (7) cannot be used when creating a layer.  They are used
         by shl when no name is supplied.  They may be abbreviated to just the
         digit.

      Commands
         The following commands may be issued from the shl prompt level.  Any
         unique prefix is accepted.

         create [ name ]
               Create a layer called name and make it the current layer.  If
               no argument is given, a layer will be created with a name of
               the form (#) where # is the last digit of the virtual device
               bound to the layer.  The shell prompt variable PS1 is set to
               the name of the layer followed by a space.  A maximum of seven
               layers can be created.
         block name [ name ... ]
               For each name, block the output of the corresponding layer when
               it is not the current layer.  This is equivalent to setting the
               stty option -loblk within the layer.
         delete name [ name ... ]
               For each name, delete the corresponding layer.  All processes
               in the process group of the layer are sent the SIGHUP signal


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   shl(1)                 (User Environment Utilities)                  shl(1)


               (see signal(2)).
         help (or ?)
               Print the syntax of the shl commands.
         layers [ -l ] [ name ... ]
               For each name, list the layer name and its process group.  The
               -l option produces a ps(1)-like listing.  If no arguments are
               given, information is presented for all existing layers.
         resume [ name ]
               Make the layer referenced by name the current layer.  If no
               argument is given, the last existing current layer will be
               resumed.
         toggle
               Resume the layer that was current before the last current
               layer.
         unblock name  [ name ... ]
               For each name, do not block the output of the corresponding
               layer when it is not the current layer.  This is equivalent to
               setting the stty option -loblk within the layer.
         quit  Exit shl.  All layers are sent the SIGHUP signal.
         name  Make the layer referenced by name the current layer.

   FILES
         /dev/sxt???       Virtual tty devices
         $SHELL            Variable containing path name of the shell to use
                           (default is /bin/sh).

   SEE ALSO
         sh(1), stty(1).
         ioctl(2), signal(2) in the Programmer's Reference Manual.
         sxt(7) in the System Administrator's Reference Manual.

   WARNING
         To avoid disabling the suspend character when in the job control
         environment, the swtch character must be redefined.



















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