PiDP-8/I Software

build and run `systemctl` commands for you when you pass it arguments:

    $ pidp8i start
    $ pidp8i stop
    $ pidp8i restart
    $ pidp8i status -l

If you run it without arguments, it attaches to the screen manager
session, just as it always has.

The last command above shows that *all* arguments are passed to
`systemctl`, not just the first, so you can pass any flags that
`systemctl` accepts.

Our systemd service starts at boot by default after you install the

    the file acts as build documentation as well as a "welcome" message.


#### --help

Run `./configure --help` for more information on your options here.


<a id="runtime"></a>
## Runtime Configuration

The `pidp8i` command may be configured by the optional `pidp8i.rc` file,
located by default in `/opt/pidp8i/etc/`.  This is a Bourne shell script
which is sourced by `pidp8i` if it exists, and recognizes the following
variables:


<a id="rc-screen-manager"></a>
### SCREEN_MANAGER=screen

By default, pidp8i installs and uses [GNU screen(1)][gnuscreen] to
manage screen sessions.  However, if you prefer to use [tmux(1)][tmux]
as a screen manager for the pidp8i session, you may set
`SCREEN_MANAGER=tmux`.  Note that if you make this change, you are
responsible for installing tmux; on Raspbian, this is done by:

        $ sudo apt-get install tmux

Switching between configured screen managers must be done while pidp8i
is stopped.

[gnuscreen]: https://www.gnu.org/software/screen/
[tmux]:      https://tmux.github.io/


## <a id="os8di"></a>The OS/8 RK05 Disk Image

For the first several years of the PiDP-8/I project, the OS/8 RK05 disk
image included with the PiDP-8/I software (called `os8.rk05`) was based
on an image of a real RK05 disk pack that someone allegedly found in a
salvaged PDP-8 system.  Parts of the image were corrupt, and not all of

#!/bin/bash
########################################################################
# pidp8i.in - Collection of scriptlets for dealing with the pidp8i
#   systemd user service and its associated screen manager session.
#
# Copyright © 2015-2019 Oscar Vermeulen and Warren Young
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,

bootdir="@BOOTDIR@"
prefix="@ABSPREFIX@"
sim="$prefix/bin/pidp8i-sim"
scanswitch="$prefix/libexec/scanswitch"
systemctl=$(uname -r | grep -qw Microsoft && echo /bin/nothing || echo /bin/systemctl)
ggrep=$(which ggrep grep 2> /dev/null | head -1)

if [ -e "$prefix/etc/pidp8i.rc" ]
then
    . "$prefix/etc/pidp8i.rc"
fi
[ -n "$SCREEN_MANAGER" ] || SCREEN_MANAGER=screen

is_running() {
    if [ "$SCREEN_MANAGER" = "tmux" ]
    then
        tmux has-session -t pidp8i 2>/dev/null
    else
        procs=`screen -list pidp8i | $ggrep -Pc '\d\.pidp8i'`
        test -n "$procs" && test $procs -gt 0 && return 0 || return 1
    fi
}

sim_child_pid() {
    if [ "$SCREEN_MANAGER" = "tmux" ]
    then
        tmux list-sessions -F '#{session_name} #{pid}' | awk '/^pidp8i / {print $2}'
    else
        screen -ls pidp8i | grep -Eo '[[:digit:]]+\.pidp8i' | grep -Eo '^[[:digit:]]+'
    fi
}

# Were we given a command line argument?
if [ -z "$1" ]
then
    # No, so just try to attach to the running simulator
    if is_running
    then
        echo Joining simulator session already in progress...
        if [ "$SCREEN_MANAGER" = "tmux" ]
        then
            exec tmux attach-session -d -t pidp8i
        else
            exec screen -r -S pidp8i
        fi
    else
        cat <<ERROR
Either the simulator isn't running, or it isn't running under a ${SCREEN_MANAGER}
session owned by @INSTUSR@.  Did you start the simulator via systemd?

ERROR
		exit 1
    fi
fi

    fi

    # We want SIMH to have a sensible working directory: somewhere the
    # user can write files and which makes sense when giving SIMH
    # commands involving file paths.  This default is chosen because it
    # satisfies both criteria.
    # If you change the default here, change that script as well.
    set -e
    cd "$prefix/share/media"
    if [ "$SCREEN_MANAGER" = "tmux" ]
    then
        tmux new-session -s pidp8i -d "$sim" "$bscript"
    else
        screen -dm -S pidp8i "$sim" "$bscript"
    fi
    if [ -x $systemctl ]
    then
        systemd-notify --ready --pid=$(sim_child_pid)
    fi
    exit 0

elif [ "$verb" = "stop" ]
then
    # Someone (maybe the user via "pidp8i stop", maybe systemd via
    # "systemctl pidp8i stop") is telling us to stop the background
    # simulator.
    #
    # First figure out what the simulator is called and send it the
    # signal that shuts it down gracefully.
    for sim in pdp8 pidp8i-sim
    do
        if pkill -0 $sim
        then
            # Give it the signal to start shutting down gracefully: stop
            # GPIO thread, save simulator state if savestate enabled...
            # Give it time to complete, then kill it hard in case it
            # doesn't die on its own.
            echo -n "Stopping $sim simulator..."
            for sig in TERM KILL ; do pkill -$sig $sim ; sleep 1 ; done

            # The screen manager might still be running despite its
            # only child dying.  Nuke it hard if so.
            if is_running
            then
                if [ "$SCREEN_MANAGER" = "tmux" ]
                then
                    tmux kill-session -t pidp8i
                else
                    screen -S pidp8i -X quit
                fi
            fi

            exit 0
        fi
    done 

    exit 1
fi