When I’m initializing routers, they generate a new SSH host key. I know the “remote” host identity has changed. This fragment gives you a command to clean up the old host key, while expressing your frustration.

.bashrc

# usage:
#     $ ssh 192.168.1.1
#     ssh: The host key has changed!!!1
#     $ fuck you, ssh
#     nop@192.168.1.1:~$ 

fuck () {
    local lastcmd=$(history -p '!!:0')
    if [ "$lastcmd" != "ssh" ]; then
        echo "The last command doesn't look like ssh."
	    set +x
	    return;
    fi;
    source "$HOME/fuck-you.sh"
    fuck_internal "$@"
}

fuck.sh

rerun_command_line=$(history -p '!!')
rerun_command=$(history -p '!!:0')
rerun_tail=$(history -p '!!:1-$')

rerun=$(bash -c "$rerun_command_line" </dev/null 2>&1 |
	    perl -n -e '/^Offending \w* key.*in ([^:]+):([0-9]+)/ && print "$1 $2\n";')

nuke_file_line () {
    if [ -z "$1" ]; then
	echo "Was the previous line an ssh invocation? I don't see it."
    fi;
    sed -i~ "$2,$2d" "$1"
}

# Intentionally not quoted.
#nuke_file_line $rerun

fuck_internal () {
    if [ "$1" != "you" ] && [ "$1" != "you," ] || [ "$2" != "ssh" ] ; then	
	echo "Usage: fuck you[,] ssh"
    else
	history_offset=$(history 1 | awk '{print $1}')
	history -d "$history_offset"
	nuke_file_line $rerun
	bash -c "$rerun_command -o 'CheckHostIP=no' -o 'StrictHostKeyChecking=no' $rerun_tail"
    fi;
}