Sh script for connecting to a machine while pinging it with a wake-on-lan package in the background every minute

mosh-mini.sh

#!/bin/sh

set -e

# How often to send wake-on-lan pokes.
POKE_INTERVAL_SECS=60

# Mac address of the machine to poke.
MAC_ADDR=00:25:4b:a0:65:9c

# Host address to connect to.
HOSTNAME=ab00

# When run as [mosh-mini.sh poke] it loops around indefinitely poking
# the machine.
if [ "$1" = "poke" ]; then
  while true; do
    wakeonlan $MAC_ADDR > /dev/null
    sleep $POKE_INTERVAL_SECS
  done
fi

# Spawn the poke job and record its PID. Be careful here -- if the
# recursive call should for some reason not park in the loop above
# this script effectively becomes a fork-bomb. This happened.
$0 poke &
POKE_PID=$!

# Ensure that the poke job is killed when this script exits.
cleanup_on_exit() {
  # Silence kill since, depending on how the signals bounce, this may be called
  # more than once. Also, the poke job may die before we exit.
  kill $POKE_PID > /dev/null 2>&1
}

# Do cleanup on normal exit and interrupt (ctrl-C).
trap cleanup_on_exit EXIT INT

# Wait for at least one successful ping before trying to
# connect. Waking up can take a while and mosh gives up quickly if the
# destination doesn't respond.
if ! ping -c1 $HOSTNAME > /dev/null; then
  echo "Host is currently unavailable; waiting for it to appear."
  while ! ping -c1 $HOSTNAME > /dev/null; do
    true
  done
fi

# Finally we've seen a successful ping to the machine. Mosh it!
mosh $HOSTNAME