A minimalist IRC client in Bash. Could also be used as a bot.

irsay.sh

#!/bin/bash 
[ -z "$channel" ] && channel="#bobot"
[ -z "$server" ] && server="irc.freenode.net"
[ -z "$port" ] && port="6667"
[ -z "$user" ] && user=$USER
 
function irc_session () {
  # Login phase
  echo "USER $user 0 * :$user"
  echo "NICK $user"
  echo "JOIN $channel"

  # User input
  while read message; do
    if [ "$message" == ".QUIT." ]; then
      break
    fi

    echo "PRIVMSG $channel :$message"
  done

  # Termination
  echo "QUIT"
}

function irc_read() {
  while read -ru 3 line; do
    echo "$line"

    # Handle PINGs
    if expr match "$line" "^PING" >/dev/null; then
      servers=`echo $line"" | cut -d: -f2`
      echo "PONG $servers" >&4
      echo "PONG $servers"
    fi
  done
}

function finish() {
  exec 3>&- 4>&-

  kill $SESSION_PID >/dev/null 2>&1
  kill $READ_PID >/dev/null 2>&1
  kill $NC_PID >/dev/null 2>&1
}

coproc NC {
  nc $server $port
}

exec 3>&${NC[0]}
exec 4>&${NC[1]}

trap finish INT

irc_session <&1 >&4 & # Feed nc with user input
SESSION_PID=$!
irc_read    <&3     & # Handle pings from IRC
READ_PID=$!

wait $NC_PID

finish