Check if one or all TLDs are available for your domain

DomainChecker.sh

#!/bin/bash
#
# Script by Parker Thomas (@Castlecorp)
#  /$$$$$$$  /$$$$$/$$$$$$$$
# | $$__  $$|__  $|__  $$__/
# | $$  \ $$   | $$  | $$
# | $$$$$$$/   | $$  | $$
# | $$____/$$  | $$  | $$
# | $$   | $$  | $$  | $$
# | $$   |  $$$$$$/  | $$
# |__/    \______/   |__/
#
# Search for open domain names
#
# boilerplate c/o @xero
#-----------------------------------------------------------------------------
# helper functions
#-----------------------------------------------------------------------------

# update this function to gracefully cleanup execution
clean_exit() {
	# grab real error code
	err=$?

	# reset traps for all signals to not interrupt destructor logic
	trap '' EXIT HUP INT QUIT PIPE TERM

	# add calls to any cleanup functions here
	clean_tempfiles

	# exit with the appropriate code
	exit $err
}

# update this handler to match your options
usage() {
	me="$(basename "$(test -L "$0" && readlink "$0" || echo "$0")")"
	printf "usage: %s <DOMAIN> [-t|-m|-j]" "$me"
	echo "    <DOMAIN>: string to use as the domain name"
    echo "    -t: a single TLD to check"
    echo "    -m: Machine readable - only output available domains"
    echo "    -j: Number of jobs to run in parallel. Default is 3"
}

# check if required commands/bins exist
function installed() {
	builtin type -P "$1" &> /dev/null
	# shellcheck disable=SC2181
	[[ $? -ne 0 ]] && return 1
	if [[ $# -gt 1 ]]; then
		shift  # we've just checked the first one
		installed "$@"
	fi
}

function requirements() {
	installed "$@" || {
        for dep in "${deps[@]}"
        do
            if ! command -v "$dep" > /dev/null; then
                echo "$dep is not installed."
            fi
        done
        exit 1;
    }
}

# main application logic
#-----------------------------------------------------------------------------
function checkArgs() {
    # Set required domain arg
    if [ $# -lt 1 ]; then usage; fi
    NAME="$1"
    shift

    # Set defaults
    MACHINE_READABLE=false
    JOBS=3

    # Parse optional flags
    while getopts 'tmj' opt; do
        case "$opt" in
            t)
                TLDs=$2
                shift 2
                ;;
            m)
                MACHINE_READABLE=true
                shift
                ;;
            j)
                JOBS="$3"
                ;;
            *)
                usage
                ;;
        esac
    done
}

# Download TLDs and save to a tempfile for reference
function getTLDs() {
    TLDs=$(mktemp /tmp/TLDs.XXXX)
    curl -s https://data.iana.org/TLD/tlds-alpha-by-domain.txt | tail -n +2 >> "$TLDs"
}

# Parameters: domain name and TLD
function resolveDomain() {
    local name=$1
    local ending=$2
    local domain="$name"."$ending"
    
    # Grep the whois result to see if it is taken
    if whois "$domain" | grep -Eq \
        '^No match|^NOT FOUND|^Not fo|AVAILABLE|^No Data Fou|has not been regi|No entri'
    then # Not taken -> echo it
        echo "$domain"
    fi

}

# If we made a tempfile, rm it
function clean_tempfiles() {
    if [ -f "$TLDs" ]; then rm -f "$TLDs"; fi
}

# Main loop
function main() {
    deps=("whois" "curl" "parallel")
    requirements "${deps[@]}"

    checkArgs "$@"

    if [ -z "$TLDs" ]; then getTLDs; # If a TLD isn't specified, get the full list
    else 
        RESULT=$(resolveDomain "$NAME" "$TLDs") # If a TLD is specified, just check that one domain
        if [ -z "$RESULT" ]; then echo "Domain not available"; else echo "$NAME.$TLDs is available"; fi
        clean_exit
    fi

    if [ "$MACHINE_READABLE" == "false" ]; then echo "Available domains:"; fi
    export -f resolveDomain # Allow the resolveDomain function to be used by parallel
    parallel --jobs "$JOBS" resolveDomain "$NAME" ::: "$(cat "$TLDs")" # Run resolveDomain on all TLDs `multithreaded`

    clean_exit
}

# runtime setup
#-----------------------------------------------------------------------------

# fail fast w/ proper exit codes
set -eo pipefail

# global error handler
trap clean_exit EXIT HUP INT QUIT PIPE TERM

# Run it
main "$@"