Remove entries from known_hosts files (including variations on the hostname)

sshrmkey.sh

#!/bin/bash
# sshrmkey.sh
#
# Little BASH tool to clean up a hostname from ssh known_hosts
#
# Shreyas Cholia - 2017-05-10 shreyas@gmail.com


# A POSIX variable
OPTIND=1         # Reset in case getopts has been used previously in the shell.
shortname=false
ip=false

show_help() {
    echo  >&2
    echo "Usage: $0 [options...] {hostname}" >&2
    echo "   -s           Clean up shortname"  >&2
    echo "   -i           Clean up IP"  >&2
    echo  >&2
    echo "sshrmkey.sh uses 'ssh-keygen -R' to clean up hostname in .ssh/known_hosts file" >&2
    exit 1
}


while getopts "h?si" opt; do
    case "$opt" in
    h|\?)
        show_help
        exit 0
        ;;
    s)  shortname=true
        ;;
    i)  ip=true
        ;;
    esac
done

shift $((OPTIND-1))
[ "$1" = "--" ] && shift

host=$@
echo "ssh-keygen -R $host"
ssh-keygen -R $host

if $shortname; then
  host_shortname=$(echo $host | cut -d. -f1)
  echo "ssh-keygen -R $host_shortname"
  ssh-keygen -R $host_shortname
fi

if $ip; then
  host_ip=$(dig +short $host)
  echo "ssh-keygen -R $host_ip"
  ssh-keygen -R $host_ip
fi