an irssi "helper" script

irc.sh

#!/bin/bash

function print_usage {
cat <<PRINT_USAGE

Usage: $(basename $0) [ -start | -restart | -check | -info ]

       -start    start ssh session (connect to remote server)
       -restart  force-restart ssh session
       -check    restart ssh session only if network settings have
                 changed since last check (use in launchd or cron)
       -info     more detailed information (version & installation)
PRINT_USAGE
}

function print_info {
cat <<PRINT_INFO

============================================================================
             ssh/screen/irc auto-restart script v1.0 - 3/22/06
               by "Cowboy" Ben Alman - http://rj3.net/cowboy/
============================================================================
$(print_usage)

Description:
This script creates a remote ssh/screen/irc session, which automatically
reconnects after ssh quits. This automatic reconnect occurs whenever ssh
disconnects (with an errorlevel != 0) OR when it gets killed by this script
in -restart or -check mode. If the screen process exits with errorlevel 0
(if detached, for example) this script will wait for a user-specified time
before auto-reconnecting.

Installation:
* Edit this script as needed (functions irc_command, irc_restart, etc).
* Ensure your ssh timeout is acceptable. For example, using these values
  in your ssh configfile might cause ssh to exit after a 2 minutes timeout:
    ServerAliveInterval 30
    ServerAliveCountMax 4
* Copy net.rj3.cowboy.irc to ~/Library/LaunchAgents and edit as needed (to
  point to the location of this script).
* Register the launch agent with this command:
    launchctl load ~/Library/LaunchAgents/net.rj3.cowboy.irc
* Start ssh/screen/irc with:
    irc -start
 
Notes:
If you don't like or have launchd, you can create a cron job to check irc.
The downside is that cron checks at most every minute, while launchd can
check every second, or when system settings (like airport) change.

Tested on OS X 10.4 Tiger, YMMV

If you have questions or suggestions, I can be found idling in efnet/#irssi.
PRINT_INFO
}

# Seconds between each retry attempt
retry_seconds=5

# Seconds before auto-reconnecting a "clean" disconnect (for example, if
# you detached the screen session from another terminal). Set to 0 to auto-
# reconnect instantly. Set to -1 to disable auto-reconnect.
retry_seconds_clean=3600

# Seconds of "good connection" after which the "reconnect attempt #N"
# counter resets. Purely for aesthetic purposes :)
countup_reset_time=60

function irc_command {
  # put your ssh/screen/irc command line here
  ssh -F ~/.ssh/config_irc -q -t [email protected] screen -rAadU IRC
}

function irc_restart {
  # edit between the quotes on the next line. what goes in there is a
  # grep pattern "guaranteed" to find your irc in the output of ps -ww
  PID=$(get_pid "ssh.*IRC")
  
  if [ "$PID" ]; then
    # note: if $PID contains multiple PIDs, this kills all of them
    kill $PID
  fi
}

function irc_check {
  if [[ $(has_network_changed) == "YES" ]]; then
    irc_restart
  fi
}

# temp file where current network info gets stored (required to keep
# irc -check from constantly restarting.
network_current_file=/tmp/irc_network_current

function irc_start {
  REPLY=
  while [[ true ]]
  do
    time_start=$(date "+%s")
  
    irc_command
    errorlevel=$?
    
    time_elapsed=$(($(date "+%s") - $time_start))
    
    if [[ $errorlevel == 0 ]]; then
      if [[ $retry_seconds_clean == -1 ]]; then
          display_echo "Press any key to reconnect..."
          read -n 1 -r -s
          display_delete
      else
        countdown=$retry_seconds_clean
        while [[ $countdown > 0 ]]
        do
          display_echo "Press any key to reconnect, or wait $(print_time $countdown)..."
          read -n 1 -t 1 -r -s
          display_delete
          
          if [[ $REPLY ]]; then
            countdown=0
            REPLY=
          else
            countdown=$(($countdown - 1))
          fi
      
        done
      fi

      countup=0
    else
      if [[ $time_elapsed > $countup_reset_time ]]; then
        countup=0
        display 1 "Disconnected!"
      else
        display 1 "Connect attempt failed!"
      fi

      countup=$((${countup:=1} + 1))
    
      countdown=$retry_seconds
      while [[ $countdown > 0 ]]
      do
        display 1 "Reconnect attempt #$countup in $(print_time $countdown)..."
    
        countdown=$(($countdown - 1))
      done
    fi
  done
}

# get the PID of a process
function get_pid {
  echo $(ps -ww | grep -v get_pid | grep -v grep | grep "$@" | awk '{print $1}')
}

# get all your ips (OS X)
function get_ip {
  echo $(ifconfig -u | grep -w "inet" | cut -d " " -f 2 | sed 's/^ *//;s/ *$//')
}

# get your airport's MAC address (OS X)
function get_bssid {
  echo $(/System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport -I | grep 'BSSID' | sed 's/.*: //')
}

# check to see if your ip(s) and/or airport connection have changed
function has_network_changed {
  #network_current_file=/tmp/irc_network_current

  network_current="$(get_bssid) $(get_ip)"
  network_previous="$(cat $network_current_file 2> /dev/null)"
  
  if [[ "$network_current" == "$network_previous" ]]; then
    echo "NO"
  else
    echo "$network_current" > $network_current_file
    echo "YES"
  fi
}

# print some text so that it can be deleted
function display_echo {
  display_text="$*"
  echo -en "$display_text"
}

# delete that text
function display_delete {
  for ((i=1;i<=${#display_text};i++)); do echo -en "\b \b"; done
}

# print text, wait, delete text
function display {
  display_echo "$2"
  sleep $1
  display_delete
}

# print days/hours/minutes/seconds instead of just seconds
function print_time {
  print_time_d=$(echo "scale=0;$1 / 86400" | bc -l)
  print_time_h=$(echo "scale=0;($1 / 3600) - ($print_time_d * 24)"  | bc -l)
  print_time_m=$(echo "scale=0;($1 / 60) - ($print_time_d * 1440) - ($print_time_h * 60)" | bc -l)
  print_time_s=$(echo "scale=0;$1 % 60" | bc -l)

  print_time_fmt=" ${print_time_d:-0} day ${print_time_h:-0} hour ${print_time_m:-0} min ${print_time_s:-0} sec"
  echo "$print_time_fmt" | sed -E "s/ 0 [^ ]*//g;s/^ //"
}

case "$1" in
  -start)   irc_start;   exit 0;;
  -check)   irc_check;   exit 0;;
  -restart) irc_restart; exit 0;;
  -info)    print_info;  exit 0;;
esac

print_usage

net.rj3.cowboy.irc

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN"
	"http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>Label</key>
	<string>net.rj3.cowboy.irc</string>
	<key>ProgramArguments</key>
	<array>
		<string>/Users/cowboy/bin/irc</string>
		<string>-check</string>
	</array>
	<key>WatchPaths</key>
	<array>
		<string>/Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist</string>
	</array>
	<key>StartInterval</key>
	<integer>5</integer>
</dict>
</plist>