Generate an Ansible Inventory for EC2 instances with a given name.

generate-ec2-inventory.sh

#!/bin/bash

if [ -z "$1" ]; then
    echo "$0 takes one argument; the value of the name tag of EC2 instances to search for." >&2
    exit 1
fi

name="$1"

# create a header for the inventory with a group name of "all"
echo "[all]" > inventory.txt

# find all instances whose "Name" tag matches $name, output their private IP addresses, translate tabs into newlines,
# and finally collect a unique list of the output and append it to the inventory, simple as that.
aws ec2 describe-instances --output text --filter "Name=tag:Name,Values=$name" \
    --query 'Reservations[].Instances[].PrivateIpAddress' | tr '\t' '\n' | uniq >> inventory.txt