get the right ubuntu ami

ubuntu-ami

#!/bin/sh

VERBOSITY=0
TEMP_D=""
NAME="ubuntu-ami"
DOT_D="$HOME/.$NAME"
CACHE_D="$HOME/.cache/$NAME"
cachelife=86400

error() { echo "$@" 1>&2; }
errorp() { printf "$@" 1>&2; }
fail() { [ $# -eq 0 ] || error "$@"; exit 1; }
failp() { [ $# -eq 0 ] || errorp "$@"; exit 1; }

Usage() {
	cat <<EOF
Usage: ${0##*/} [ options ] criteria

   Get the latest Ubuntu ami meeting certain criteria

   options:
      -o | --output FILE    output to file rather than stdout
      -f | --format format  change output to 'format'.
                            default: '%{ami}'

   Examples:
   - get the latest ami matching default criteria for release 'n'
     $ ${0##*/} -v n
     release=natty bname=server store=ebs region=us-east-1 arch=amd64 ptype=paravirtual stream=released
     ami-1aad5273
   - get an instance-store image in i386 image in us-west-1
     $ ${0##*/} lucid i386 instance us-west-1
     ami-73c69436
   - get the latest daily build of the devel release in eu-west-1
     $ EC2_REGION=eu-west-1 ${0##*/} daily amd64 ebs o

EOF
}

bad_Usage() { Usage 1>&2; [ $# -eq 0 ] || error "$@"; exit 1; }
cleanup() {
	[ -z "${TEMP_D}" -o ! -d "${TEMP_D}" ] || rm -Rf "${TEMP_D}"
}

cache_valid() {
	local file="$1" date="$2"
	[ -n "$file" -a -e "$file" ] || return 1
	touch --date "${date}" "${TEMP_D}/ts"
	[ "$file" -nt "$TEMP_D/ts" ]
}

dlcache() {
	local url="$1" out="$2" cfilename="$3" age="$4"
	local cachef="${CACHE_D}/$cfilename"
	local timeout="now - $age seconds"
	[ -n "$cfilename" ] || cachef=""
	if cache_valid "$cachef" "$timeout"; then
		cp -a "$cachef" "$out"
		return
	fi
	wget -q "${url}" -O "${out}" || return 1
	{ [ -z "$cachef" ] || cp "${out}" "${cachef}"; } ||
		return 1
}

debug() {
	local level=${1}; shift;
	[ "${level}" -gt "${VERBOSITY}" ] && return
	error "${@}"
}

isrel() {
	local cand="$1" url="$2" out="$3" cache="$4" age="$5"
	local o="" f=""
	for f in "$out" "$CACHE_D/$cache"; do
		[ -f "${f}" ] &&
			o=$(awk '-F\t' '$1 ~ r { print $1; exit(0); }' "r=^$cand" "$f") &&
			[ -n "$o" ] && _RET="$o" && return 0
	done
	dlcache "$url" "$out" "$cache" "$age" &&
		o=$(awk '-F\t' '$1 ~ r { print $1 }' "r=^$cand" "$out")  &&
		[ -n "$o" ] && _RET="$o" && return 0
	return 1
}
subst() {
	local cur="$1"; shift;
	while [ $# -ne 0 ]; do
      while [ "${cur#*${1}}" != "${cur}" ]; do
         cur="${cur%%${1}*}${2}${cur#*${1}}"
      done
		shift 2
	done
	_RET=${cur}
}

short_opts="f:ho:v"
long_opts="format:,help,no-cache,output:,verbose"
getopt_out=$(getopt --name "${0##*/}" \
	--options "${short_opts}" --long "${long_opts}" -- "$@") &&
	eval set -- "${getopt_out}" ||
	bad_Usage

## <<insert default variables here>>
output="-"
format='%{ami}'
burl="https://cloud-images.ubuntu.com/query"
store="ebs"
region_default="${EC2_REGION:-us-east-1}"
release="lucid"
arch="amd64"
stream="released"
bname="server"
itype=""
ptype="paravirtual"
poss_release=""

while [ $# -ne 0 ]; do
	cur=${1}; next=${2};
	case "$cur" in
		-h|--help) Usage ; exit 0;;
		-f|--format) format=${2}; shift;;
		-o|--output) output=${2}; shift;;
		-v|--verbose) VERBOSITY=$((${VERBOSITY}+1));;
		   --no-cache) cachelife=0;;
		--) shift; break;;
	esac
	shift;
done

for i in "$@"; do
	case $i in
		lucid|karmic|hardy|maverick|natty|oneiric) r_rel=${i};;
		rel*) stream="released";;
		daily) stream=${i};;
		server|desktop) bname=${i};;
		i386|amd64|x86_64) arch=${i}; [ "${i}" = "x86_64" ] && arch="amd64";;
		*-*-[0-9]) region=${i};;
		ebs) store="$i";;
		instance|instance-store) store="instance-store";;
		hvm) ptype="hvm";;
		para|paravirtual) ptype="paravirtual";;
		c[cg][1-9].*)
			ptype="hvm";
			arch=amd64;;
		[a-z][1-9].[0-9a-z]*|c[cg][1-9].*)
			case "${i}" in
				t1.micro) store=ebs;; # t1.micro does not imply arch
				m1.small|c1.medium) arch=i386;;
				*) arch=amd64;;
			esac
			;;
		http://*|https://*) burl=${i};;
		[hklmnopqrstuvwxyz])
			[ -z "$p_rel" ] || fail "found 2 unknown args: $p_rel, $i";
			p_rel=$i;;
		*) fail "confused by argument: ${i}";;
	esac
done

TEMP_D=$(mktemp -d "${TMPDIR:-/tmp}/${0##*/}.XXXXXX") ||
	fail "failed to make tempdir"
trap cleanup EXIT

{ [ -d "${CACHE_D}" ] || mkdir -p "${CACHE_D}"; } ||
	fail "failed to create ${CACHE_D}"

daily_latest="${TEMP_D}/daily.latest.txt"
release_latest="${TEMP_D}/released.latest.txt"

if [ -n "$p_rel" ]; then
	[ -z "$r_rel" ] || fail "unknown arg ${p_rel}"
	url="${burl}/daily.latest.txt"
	isrel "$p_rel" "$url" "${daily_latest}" "daily.latest.txt" $cachelife &&
		r_rel="${_RET}" || fail "bad input $p_rel"
fi
[ -n "$r_rel" ] && release=$r_rel

if [ -z "${region}" ]; then
	if [ -n "${EC2_URL}" ]; then
		case "${EC2_URL#*://}" in
			*-*-[0-9].ec2.amazonaws.com*)
				region=${EC2_URL#*://};
				region=${region%%.*};;
			ec2.amazonaws.com/*) region=us-east-1;;
		esac
	else
		region="${region_default}"
	fi
fi

ec2_curf="${TEMP_D}/${release}.${bname}.${stream}.current.txt"
ec2_url="${burl}/${release}/${bname}/${stream}.current.txt"
dl_curf="${TEMP_D}/${release}.${bname}.${stream}-dl.current.txt"
dl_url="${burl}/${release}/${bname}/${stream}-dl.current.txt"

dlcache "${dl_url}" "${dl_curf}" "${dl_curf##*/}" $cachelife ||
	fail "failed to get ${url}"

out=$(awk '-F\t' \
	'$1 == release && $2 == bname && $5 == arch { print $4, $6, $7 }' \
	"release=$release" "bname=$bname" "arch=$arch" "${dl_curf}") &&
	[ -n "$out" ] || fail "failed find entry in ${dl_url}"
set -- ${out}; serial=$1; dlpath=$2; pubname=$3
url="${burl%/query}/${dlpath}"

prefix="${store}"
[ "${ptype}" = "hvm" ] && prefix="hvm"
dlcache "${ec2_url}" "${ec2_curf}" "${ec2_curf##*/}" $cachelife ||
	fail "failed to get ${ec2_url}"
ami=$(awk '-F\t' \
	'$1 == release && $2 == bname && $5 == store &&
	$6 == arch && $7 == region && $11 == ptype { print $8 }' \
	"release=$release" "bname=${bname}" \
	"store=$store" "arch=$arch" "region=$region" "ptype=$ptype" \
	"${ec2_curf}") && [ -n "$out" ] || fail "failed to find image"

subst "$format" \
  '%{ami}' "$ami" \
  '%{arch}' "$arch" '%{bname}' "$bname" '%{dlpath}' "$dlpath" \
  '%{ptype}' "$ptype" '%{pubname}' "$pubname" '%{region}' "$region" \
  '%{release}' "$release" '%{store}' "$store" '%{stream}' "$stream" \
  '%{url}' "$url"

out=${_RET}
[ -n "${out}" ] || fail "no ami found matching criteria"

debug 1 "${region}/${prefix}/${pubname}"
if [ -n "${output}" -a "${output}" != "-" ]; then
	echo "$out" > "$output"
else
	echo "$out"
fi
exit
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