shl(1)             UNIX System V(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 (see
            signal(2)).



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shl(1)             UNIX System V(User Environment Utilities)             shl(1)


      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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