SHL(C)                   XENIX System V                    SHL(C)



     Name
          shl - Shell layer manager

     Syntax
          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 that 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(C) 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 that has been bound to a virtual tty
          device (/dev/sxt???).  The virtual device can be manipulated
          like a real tty device using stty(C) and ioctl(S).  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, or, if superuser, the name
               followed by a sharp (#) and 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



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     SHL(C)                   XENIX System V                    SHL(C)



               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)).

          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
          ioctl(S), sh(C), signal(S), stty(C), sxt(M)

     Note
          It is inadvisable to kill shl.










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