shl(1)
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shl Command
shell layer manager in DG/UX
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SYNTAX
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
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shl(1)
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)).
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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