ssh-save-id

#!/bin/sh

# Copyright (c) 2018 Vadiem Janssens <info@vadiemjanssens.nl>
#
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

# Shell script to save a ssh-connection to your ssh-config file

usage () {
  printf 'Usage: %s [-h|-n] [-p port] user@hostname\n' "$0" >&2
  printf '\t-n: dry run    -- no aliasses are actually saved\n' >&2
  printf '\t-h: print this help\n' >&2
  exit 1
}

unset DRY_RUN PORT USERHOST USER HOST OUTPUT CONFIG_FILE

OPTIND=1
while getopts 'np:?h' c
do
  case $c in
    n) DRY_RUN=1 ;;
    p) PORT=$OPTARG ;;
    h|?) usage ;;
    \?) echo "Invalid option: -$OPTARG" >&2; return 1;;
  esac
done
shift $((OPTIND-1))

if [ -z "$1" ]; then USERHOST=""; else USERHOST="$1"; fi

if [ $# = 0 ] ; then
  usage
fi

CONFIG_FILE="${HOME}/.ssh/config"

USER=$(echo $USERHOST | cut -f1 -d@)
HOST=$(echo $USERHOST | cut -f2 -d@)

build_output() {
  OUTPUT="Host $HOST"$'\n'
  OUTPUT=$OUTPUT"    hostname $HOST"$'\n'
  OUTPUT=$OUTPUT"    user $USER"

  if [ "$PORT" ] ; then
    OUTPUT=$OUTPUT$'\n'"    port $PORT"
  fi
}

write_output() {
  if ! [ "$DRY_RUN" ] ; then
    echo "$OUTPUT" >> $CONFIG_FILE
  fi
}

build_output
write_output

if [ "$DRY_RUN" ] ; then
  cat <<-EOF
	=-=-=-=-=-=-=-=
	Would have added the following to ~/.ssh/config:

	$OUTPUT

	Re-run the command without -n to apply the changes
	=-=-=-=-=-=-=-=
	EOF
else
  cat <<-EOF
	=-=-=-=-=-=-=-=
	Added the following to ~/.ssh/config:

	$OUTPUT

	Now try logging into the machine, with:   "ssh $HOST"
	=-=-=-=-=-=-=-=
	EOF
fi