#!/bin/bash
#
#    10-sysinfo - generate the system information
#    Copyright (c) 2013 Nick Charlton
#
#    Authors: Nick Charlton <hello@nickcharlton.net>
#    Modified by Oitibs: https://oitibs.com/?s=Debian+Dynamic+MOTD
#    Modified by Leitbogioro: https://github.com/leitbogioro/
#                             https://www.zhihu.com/column/originaltechnic
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License along
#    with this program; if not, write to the Free Software Foundation, Inc.,
#    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
date=`date`
load=`cat /proc/loadavg | awk '{print $1}'`
root_usage=`df -h / | awk '/\// {print $(NF-1)}'`
memory_usage=`free -m | awk '/Mem:/ { total=$2; used=$3 } END { printf("%3.1f%%", used/total*100)}'`
 
swap_usage=`free -m | awk '/Swap/ { printf("%3.1f%%", $3/$2*100) }'`
users=`users | wc -w`
time=`uptime | grep -ohe 'up .*' | sed 's/,/\ hours/g' | awk '{ printf $2" "$3 }'`
processes=`ps aux | wc -l`
localip=`hostname -I | awk '{print $1}'`

IPv4=`timeout 1 dig -4 TXT +short o-o.myaddr.l.google.com @ns1.google.com | sed 's/\"//g'`
IPv6=`timeout 1 dig -6 TXT +short o-o.myaddr.l.google.com @ns1.google.com | sed 's/\"//g'`
# IP_Check=$(echo $IPv4 | awk -F. '$1<255&&$2<255&&$3<255&&$4<255{print "isIPv4"}')
IP_Check="$IPv4"
if expr "$IP_Check" : '[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*$' >/dev/null; then
  for i in 1 2 3 4; do
    if [ $(echo "$IP_Check" | cut -d. -f$i) -gt 255 ]; then
      echo "fail ($IP_Check)"
      exit 1
    fi
  done
  IP_Check="isIPv4"
fi

# If the last two strings of IPv6 is "::", we should replace ":" to "0" for the last string to make sure it's a valid IPv6(can't end with ":").
[[ ${IPv6: -1} == ":" ]] && IPv6=$(echo "$IPv6" | sed 's/.$/0/')
# If the first two strings of IPv6 is "::", we should replace ":" to "0" for the first string to make sure it's a valid IPv6(can't start with ":").
[[ ${IPv6:0:1} == ":" ]] && IPv6=$(echo "$IPv6" | sed 's/^./0/')
# Add ":" in the last of the IPv6 address for cut all items infront of the ":" by split by symbol ":".
IP6_Check="$IPv6"":"
# Total numbers of the hex blocks in IPv6 address includes with empty value(abbreviation of "0000").
IP6_Hex_Num=`echo "$IP6_Check" | tr -cd ":" | wc -c`
# Default number of empty values of the hex block is "0".
IP6_Hex_Abbr="0"
# The first filter plays a role of:
# 1. check if 0-9 or a-z and ":" in original IPv6;
# 2. the longest number of ":" in IPv6 is "7", because of variable "IP6_Check" one more ":" has been add,
# so the total number of ":" in variable "IP6_Check" should be less or equal "8".
if [[ `echo "$IPv6" | grep -i '[[:xdigit:]]' | grep ':'` ]] && [[ "$IP6_Hex_Num" -le "8" ]]; then
# Total cycles of the check(sequence of the current hex block).
  for ((i=1; i<="$IP6_Hex_Num"; i++)){
# Every IPv6 hex block of current cycle.
    IP6_Hex=$(echo "$IP6_Check" | cut -d: -f$i)
# Abbreviation of hex block should be appeared only one time in principle.
    [[ "$IP6_Hex" == "" ]] && IP6_Hex_Abbr=`expr $IP6_Hex_Abbr + 1`
# String number of letters or numbers in one block should less or equal "4".
    [[ `echo "$IP6_Hex" | wc -c` -le "4" ]] && {
# The second filter plays a reversion role of the following to exclude an effective IPv6 hex block:
# 1. Except 0-9 and a-f;
# 2. Abbreviation of hex block should be appeared less than or equal one time.
      if [[ `echo "$IP6_Hex" | grep -iE '[^0-9a-f]'` ]] || [[ "$IP6_Hex_Abbr" -gt "2" ]]; then
        echo "fail ($IP6_Check)"
        exit 1
      fi
    }
  }
  IP6_Check="isIPv6"
fi

if [[ "${IP6_Check}" != "isIPv6" ]] && [[ -z ${IPv6} ]]; then
  IPv6="N/A"
fi

if [[ "${IP_Check}" != "isIPv4" ]] && [[ -z ${IPv4} ]]; then
  IPv4="N/A"
fi

if [[ "${localip}" == "${IPv4}" ]] || [[ "${localip}" == "${IPv6}" ]]; then
  # localip=`ip -o a show | grep -w "lo" | grep -w "inet" | cut -d ' ' -f7 | awk '{split($1, a, "/"); print $2 "" a[1]}'`
  localip=`cat /etc/hosts | grep "localhost" | sed -n 1p | awk '{print $1}'`
fi

echo " System information as of $date"
echo
printf "%-30s%-15s\n" " System Load:" "$load"
printf "%-30s%-15s\n" " Private IP address:" "$localip"
printf "%-30s%-15s\n" " Public IPv4 address:" "$IPv4"
printf "%-30s%-15s\n" " Public IPv6 address:" "$IPv6"
printf "%-30s%-15s\n" " Memory Usage:" "$memory_usage"
printf "%-30s%-15s\n" " Usage On /:" "$root_usage"
printf "%-30s%-15s\n" " Swap Usage:" "$swap_usage"
printf "%-30s%-15s\n" " Local Users:" "$users"
printf "%-30s%-15s\n" " Processes:" "$processes"
printf "%-30s%-15s\n" " System Uptime:" "$time"
echo