Script to create bash aliases for hostnames in ssh config and known_hosts files

ssh_alias.sh

#!/bin/bash
# Script to create bash aliases for hostnames in ssh config and known_hosts files
# Original fom http://samrowe.com/wordpress/2008/07/29/bash-ssh-happiness/
# Updated by ja@vanhaarst.net
# Example usage:
# ALIAS_TEMP=$(mktemp);bash ssh_alias.sh | sort -r > $ALIAS_TEMP;source $ALIAS_TEMP;rm $ALIAS_TEMP;alias

set -o errexit  # Exit on error
set -o nounset  # Exit on use of unset variable
#set -o verbose  # Prints shell input lines as they are read.
#set -o xtrace   # Print command traces before executing command.

shopt -s extglob # Turn on extended globbing

# Function to check whether input is an integer
isint(){
    case $1 in
        ?([-+])+([0-9]) )
            return 0;;
        *) return 1;;
            esac
}

if [[ -d ~/.ssh ]]; then

    # Touch files we expect to exist
    if [[ ! -e ~/.ssh/config ]]; then touch ~/.ssh/config; fi
    if [[ ! -e ~/.ssh/known_hosts ]]; then touch ~/.ssh/known_hosts; fi

    # Parse ~/.ssh/known_hosts and ~/.ssh/config to find unique hosts
    for x in $(echo $(sed -e 's/[, ].*//' ~/.ssh/known_hosts; awk '/^Host [^*?]+$/{print $2}' ~/.ssh/config) | tr ' ' '\n'  | sort | uniq); do
        # Remove the domainname, and leave only the first octet of an IPv6 adress
        y=$(echo ${x} | cut -f 1 -d'.' | cut -f 1 -d':')
        # you don't want IP addresses for aliases, trust me.
        isint "${y}" && continue

        # If it's a short-name, move on
        #z=${x##*.}
        #[[  "${z}" == 'edu' ||  "${z}" == 'com' || "${z}" == 'net' ]] || continue
        # So the above is commented out because you'd be surprised at how much 
        # you rely on your search path. You should pipe the output of this script to
        # sort and your fqdn's will override your shorts.

        # Check for existing commands with the same name
        type "${y}" > /dev/null 2>&1 && continue
        
        # Return alias command
        echo alias "${y}"="'ssh ${x}'"
    done
fi