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.ig
	@(#)dpy.1	2.1	7/1/84
	@(#)Copyright (C) 1983 by National Semiconductor Corp.
..
.TH DPY 1
.SH NAME
dpy \- display the output of a command repeatedly
.SH SYNOPSIS
.B dpy
[ -a# ] [ -d ] [ -o# ] [ -s# ] [ -t ] command [ arg ... ]
.SH DESCRIPTION
.I Dpy
executes the given command repeatedly while displaying the output of the
command to the terminal.  This is done with minimal changes to the screen
by using the
.IR curses (3)
subroutine package.  When given commands such as
.IR ps (1)
or
.IR w (1),
you can produce a continuously updating status of the system.
.PP
In order to increase the speed of the program,
.I dpy
executes the command directly without the involvement of any shell.  This
does not affect most commands, since the arguments are expanded by the
shell before
.I dpy
is run.  However, if you need repeated argument expansion (such as in the
command "ls *"), want to run multiple commands in series, or want to
pipe the output of one program into another, then you need to run a shell.
This is done by running the shell explicitly, as in the
examples 'dpy csh -cf "ls *"' and 'dpy sh -c "ls *"'.
.PP
To prevent excessive loading of the system,
.I dpy
sleeps between each execution of the command.  The default sleep time is
10 seconds.  This can be changed by using the -s option, which takes the
desired sleep time in seconds (the letter 's' is optional). The top line of
the display usually contains a title line which describes the command being
executed, the sleep time, and the date.  The -t option removes the title
line completely, while the -d option removes just the date.  Normally, only
the first screenful (page) of the command output can be seen.  This can be
changed by using the -a option, which automatically advances to the next page.
Its argument is the number of updates to make between page advancements.
To provide a sense of continuity, the last line of the old screen is normally
also shown as the top line of the new screen to provide a one line overlap.
The -o option can be used to change this overlap value.
.PP
Commands can be given to
.I dpy
while it is running.  Such commands do not echo, are self-terminating
(no return is necessary), and can be edited before completion by using
the erase and kill characters.
The return character updates the screen immediately.
The space character advances to the next page of data.
The sequence '#s', where '#' is a number, sets a new sleep time.
The sequence '#p' shows the specified page of data.
The sequence '#a' sets automatic page advancment for every '#' updates.
The sequence 'na' turns off automatic page advancement.
The sequence '#o' sets the number of lines of overlap between pages.
The sequence 'nt' turns off the title line, while the character 't' restores it.
The sequence 'nd' turns off the date, while the character 'd' restores it.
The character '^L' refreshes the screen.
The character 'q' (or the interrupt character) exits.
The character 'i' initializes all parameters to their default values.
.PP
As long as no commands are being typed, the sleep time increases at the
rate of one second per minute, up to a maximum of one minute.  Typing
any command restores the desired sleep time.  This feature reduces the
load on the system when users walk away from the program.
.SH BUGS
Fast typing causes the screen to blank out briefly.  This is due to the
"feature" of the curses package of not updating when input is ready.
.PP
Since
.I dpy
does not show any output until a command has exited, running commands which
never exit (such as
.IR vmstat (1))
is pointless.
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