copykey

#!/bin/bash
#
# copykey
#

[ -n "$MYDIR" ] || {
	declare MYDIR=
	MYDIR="$(dirname "$(readlink -f "$0")")"
}
declare remote_user
declare remote_host
declare -a argv=()
declare -i argc=2

declare usagestr="$(
cat <<EOF

$(basename "$0") remote_user remote_host

Arguments
---------
   remote_user : username on the remote host
   remote_host : ip of the remote host

\0
EOF
)"

usage() {
	echo -e "$usagestr"
}

# control_c: run if user hits control-c
#
# Global
#   CTLC_EXIT - bash environment variable
#
control_c() {
	echo -e "\nCtrl-c detected\nCleaning up and exiting."
	exit $CTLC_EXIT
}

# exitme
#
# Arguments
#   $1 - exit code
#   $2 - optional message
#
exitme() {
	local -i code="$1"
	local msg="$2"

	((code == 0)) && exit "$code"
	echo -e "$msg"
	usage
	exit "$code"
}

# check_arg
#
# Globals:
#   argv - array containing command line arguments
#
check_arg() {
        local arg="$1"

        # If 1st char is a hyphen, then invalid switch
        [ "${arg:0:1}" == "-" ] && return 1

        # Otherwise, add the arg to the argary
        argv+=("$arg")
        return 0
}

# parseopts
#
# Globals
#   argv
#   argc
#
parseopts() {
	while (($# > 0)); do
	    case "$1" in
		-h | --help )
		     echo -e "$usagestr"
		     exit 0
		     ;;
		* )  argv+=("$1")
		     ;;
	    esac
	    shift
	done
}

main() {
        # Trap for control-c
        trap control_c SIGINT

	parseopts "$@"
	remote_user="${argv[0]}"
	remote_host="${argv[1]}"

	### Detailed Explanation:

	# `LOCAL_HOST=$(hostname)`: This captures the hostname of your local machine.
	# `localkey=$(cat ~/.ssh/id_rsa.pub)`: This captures the content of your public key.

	# `remote_script`: This is a here document that contains the script to
	# be run on the remote host.
	#
	# - Ensures the `.ssh` directory exists.
	# - Appends the local public key to the `authorized_keys` file.
	#
	# - Uses `ssh-keyscan` to add the local host's public key to the
	#   `known_hosts` file on the remote host.
	#
	# - Sets the correct permissions for the `authorized_keys` file and the
	#   `.ssh` directory.
	#
	# `ssh -o "StrictHostKeyChecking=no" $remote_user@$remote_host "$remote_script"`
	#  - connects to the remote host and runs the script.

	### Script to Automate the Process

	key=${3:-~/.ssh/id_rsa.pub}

	if [ -z "$remote_user" ] || [ -z "$remote_host" ]; then
	echo "Usage: $0 <remote_user> <remote_host> [ssh_key_path]"
	exit 1
	fi

	LOCAL_HOST=$(hostname)
	localkey=$(cat "$key")

remote_script=$(cat <<EOF
mkdir -p ~/.ssh
echo "$localkey" >> ~/.ssh/authorized_keys
ssh-keyscan -H $LOCAL_HOST >> ~/.ssh/known_hosts
chmod 600 ~/.ssh/authorized_keys
chmod 700 ~/.ssh
EOF
)

ssh -o "StrictHostKeyChecking=no" "$remote_user@$remote_host" "$remote_script"
	exitme 0
}

main "$@"