shl(1)                     DG/UX 4.30                      shl(1)



     NAME
          shl - shell layer manager in DG/UX

     SYNOPSIS
          shl

     DESCRIPTION
          Shl lets a user 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 can receive input from the keyboard.
          Other layers trying to read from the keyboard are blocked.
          Output from multiple layers is multiplexed onto the
          terminal.  To block the output of a layer when it is not
          current, set the stty option loblk within the layer.

          The stty character swtch (set to ^Z if NUL) switches 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/ttyp??).  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
          You can issue the following commands 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 a digit
               (1,2...7) 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



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     shl(1)                     DG/UX 4.30                      shl(1)



               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/ttyp??       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 for the
          DG/UX System
          pty(7) in the System Manager's Reference for the DG/UX
          System





















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