LAYERS(C) UNIX System V
Name
layers - layer multiplexer for windowing terminals
Syntax
layers [-s] [-t] [-d] [-p] [-f file] [layersys-prgm]
Description
The layers command manages asynchronous windows [see
layers(M)] on a windowing terminal. Upon invocation, layers
finds an unused xt(HW) channel group and associates it with
the terminal line on its standard output. It then waits for
commands from the terminal.
Command-line options:
-s Reports protocol statistics on standard error at the
end of the session after you exit from layers. The
statistics may be printed during a session by
invoking the program xts(ADM).
-t Turns on xt(HW) driver packet tracing, and produces
a trace dump on standard error at the end of the
session after you exit from layers. The trace dump
may be printed during a session by invoking the
program xtt(ADM).
-d If a firmware patch has been downloaded, prints out
the sizes of the text, data, and bss portions of the
firmware patch on standard error.
-p If a firmware patch has been downloaded, prints the
downloading protocol statistics and a trace on
standard error.
-f file Starts layers with an initial configuration
specified by file. Each line of the file represents
a layer to be created, and has the following format:
origin_x origin_y corner_x corner_y command_list
The coordinates specify the size and position of the
layer on the screen in the terminal's coordinate
system. If all four are 0, the user must define the
layer interactively. command_list, a list of one or
more commands, must be provided. It is executed in
the new layer using the user's shell (by executing:
$SHELL -i -c "command_list"). This means that the
last command should invoke a shell, such as /bin/sh.
(If the last command is not a shell, then, when the
last command has completed, the layer will not be
functional.)
layersys-prgm
A file containing a firmware patch that the layers
command downloads to the terminal before layers are
created and command_list is executed.
Each layer is in most ways functionally identical to a
separate terminal. Characters typed on the keyboard are
sent to the standard input of the UNIX system process
attached to the current layer (called the host process), and
characters written on the standard output by the host
process appear in that layer. When a layer is created, a
separate shell is established and bound to the layer. If
the environment variable SHELL is set, the user will get
that shell, otherwise, /bin/sh will be used. In order to
enable communications with other users via write(C), layers
invokes the command relogin(ADM) when the first layer is
created. relogin(ADM) will reassign that layer as the
user's logged-in terminal. An alternative layer can be
designated by using relogin(ADM) directly. layers will
restore the original assignment on termination.
Layers are created, deleted, reshaped, and otherwise
manipulated in a terminal-dependent manner. For instance,
the AT&T TELETYPE 5620 DMD terminal provides a mouse-
activated pop-up menu of layer operations. The method of
ending a layers session is also defined by the terminal.
Example
layers -f startup
where startup contains
8 8 700 200 date ; pwd ; exec $SHELL
8 300 780 850 exec $SHELL
Notes
The xt(HW) driver supports an alternate data transmission
scheme known as ENCODING MODE. This mode makes layers
operation possible even over data links which intercept
control characters or do not transmit 8-bit characters.
ENCODING MODE is selected either by setting a configuration
option on your windowing terminal or by setting the
environment variable DMDLOAD to the value hex before running
layers:
export DMDLOAD; DMDLOAD=hex
If, after executing layers -f file, the terminal does not
respond in one or more of the layers, often the last command
in the command-list for that layer did not invoke a shell.
When invoking layers with the -s, -t, -d, or -p options, it
is best to redirect standard error to another file to save
the statistics and tracing output (e.g., layers -s 2>stats);
otherwise all or some of the output may be lost.
Files
/dev/xt??[0-7]
/usr/lib/layersys/lsys.8;7;3
/usr/lib/layersys/lsys.8;?;?
See Also
relogin(ADM), sh(C), write(C), wtinit(ADM), xts(ADM),
xtt(ADM), xt(HW), libwindows(S), layers(M)
(printed 2/15/90) LAYERS(C)