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⬅️ Previous capture (2021-12-04)
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i am always keen to learn so i am open to suggestions for improvement. one of the points for me writing this script was to keep the process simple, understandable, well commented, and for me to learn. i will likely smile politely and then ignore suggestions to get this done in one line of [your favourite lang] and regex's:-)
#!/bin/bash
# getpublicip.sh
#
# what this does
#
# get a public ip using a source randomly (sorta) selected
# from a text file of public ip urls: publicipsources.txt
# but change that filename if you want
# we are playing nice and not bothering any source too much
# check a log for our last ip
# if it has changed
# log the date time source url and ip: publicip.log
# change that filename if you want
# publicip log uses space as a delimiter
# change DEFAULT_PUBLIC_IP_SOURCE to whatever you want
# use absolute pathnames if you are going to cron this
#
# this script will expect a file with public ip sources but
# will make it's own if necessary and not break
#
# useage
#
# if you extracted this from the tar.gz then this will
# be in a directory: publicipscript
# make the script executable and run it
# or run it from bash or sh
# or make the script executable and run it from cron
#
# changelog
#
# 20210302: first working version
# 20210304:
# - changed var names closer to bash convention
# - added file exists check for sources and a default source
# 20210306:
# - added line to remove whitespace from curl response
# - added check for empty or non numeric first char
# curl response and set to "fail..."
# - added even more comments for clarity re curl
# 20210312:
# - fixed bug for detecting first ip digit: it can be 0-9
# 20210313:
# - changed date format to +%Y-%m-%d-%H:%M
# - moved some comments to the top of the file
# - added usage
# 2021-03-16:
# - changed date format again to be isoish: -u +%FT%TZ
#
#####################################################################
#####################################################################
# Copyright [2021] [neil c timms]
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.#
#####################################################################
#####################################################################
# how not to write a bash script or get this done efficiently:-)
#
# var for publicip.log, sources, and defaults
PUBLIC_IP_LOG=publicip.log
PUBLIC_IP_SOURCES=publicipsources.txt
last_ip="none"
DEFAULT_PUBLIC_IP_SOURCE="http://ifconfig.me"
#
# check that our publicip.log exists
if [ -f "$PUBLIC_IP_LOG" ]; then
# save our last ip from publicip.log
last_ip=$(tail -1 $PUBLIC_IP_LOG | awk '{print $3}')
fi
# if it doesn't exist then we already have a last_ip
# and will write PUBLIC_IP_LOG anyway so no need to make it now
#
# check that the publicipsources.txt file exists else make it
# else make our sources file using our default source
# get a random public ip source url for publicipsources.txt
if [ -f "$PUBLIC_IP_SOURCES" ]; then
ip_source=$(shuf -n 1 $PUBLIC_IP_SOURCES)
else
# we will make our PUBLIC_IP_SOURCES file
# and set an ip_source
echo $DEFAULT_PUBLIC_IP_SOURCE >> $PUBLIC_IP_SOURCES
ip_source=$DEFAULT_PUBLIC_IP_SOURCE
fi
#
# curl the public ip_source to set public_ip using curl option -s, silent
# if curl fails to get a valid ip then public_ip can be empty
# so we could check if empty with [ -z etc...
# for info -n will check if not empty
# but what if we get a webpage back and it starts with <? so
# if public_ip doesn't start with 0-2 as an ip should
# set it to "fail.etc" this also works if empty
public_ip=$(curl -s $ip_source)
# strip off any whitespace that might be there, or not
public_ip="${public_ip//[[:space:]]/}"
if [[ ! $public_ip =~ ^[0-9] ]]
then
public_ip="fail.to.get.ip"
fi
#
# if the ip changed then log the new ip else do nothing
if [ "$last_ip" != "$public_ip" ]
then
# log the date time and public ip to publicipsources.txt
# we use >> to make publicip log if missing
echo "$(date -u +%FT%TZ) $ip_source $public_ip" >> $PUBLIC_IP_LOG
# for debugging uncomment the next two lines for logging all gets
# else
# echo "$(date -u +%FT%TZ) $ip_source $public_ip" >> $PUBLIC_IP_LOG
fi
# exit - that's all folks!
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