List terraform versions available (from GitHub releases).

terraform-releases.sh

#!/bin/bash -e
#
# Lists terraform releasesusing GitHub API.

APP_NAME=$(basename $0)
APP_VERSION="1.0.0"
OPTION_NUMBER_ONLY=""
OPTION_STABLE_ONLY=""
OPTION_ORDER=""

[[ -n "${DEBUG}" ]] && { set -x; }

# Usage: display_help
display_help()
{
	cat <<-EOT
	Usage: ${APP_NAME}
	       ${APP_NAME} <-h|--help>
	       ${APP_NAME} <-v|--version>
	       ${APP_NAME} [options]

	Will output latest terraform releases on GitHub.

	Options:
	  -v | --version      Displays script version information.
	  -h | --help         Displays this message.
	  -n | --number-only  Removes "v" prefix from versions.
	  -s | --stable-only  Avoids alpha, beta and release candidates.
	  -o | --order        Numerical order versions, olders first.

	Bugs and suggestions can be sent to https://github.com/augustohp.
	EOT
}

# Usage: assert_environment
assert_environment()
{
	for dependency in curl jq sed
	do
		command -v "${dependency}" 2>&1 > /dev/null \
			|| { echo "Error! Missing dependency ${dependency}." >&2; exit 42; }
	done
}

# Usage: list_latest_releases | filter_stable_releases
filter_stable_releases()
{
	if [ -n $OPTION_STABLE_ONLY ]
	then
		grep -v '\-alpha' \
			| grep -v '\-beta' \
			| grep -v '\-rc'
	fi
}

# Usage: list_latest_releases | filter_numbers_only
filter_numbers_only()
{
	if [ -n $OPTION_NUMBER_ONLY ]
	then
		sed 's/^v//'
	fi
}

# Usage: list_latest_releases | filter_order
filter_order()
{
	if [ -n $OPTION_ORDER ]
	then
		sort
	fi
}

# Usage: list_latest_releases
list_latest_releases()
{
	assert_environment

	curl \
		--silent \
		-H "Accept: application/vnd.github.v3+json" \
		https://api.github.com/repos/hashicorp/terraform/releases \
		| jq ".[] | .tag_name" \
		| sed 's/"//g' \
		| filter_numbers_only \
		| filter_stable_releases \
		| filter_order
}

# Parses options and arguments
while :;
do
	# If no argument/option left, stop
	if [ $# -eq 0 ]
	then
		break
	fi
	# Matches current option/argument, configuring environment
	case "$1" in
		-h|--help|help)
			display_help
			exit 1
			;;
		-v|--version|version)
			echo "${APP_NAME} ${APP_VERSION}"
			exit 1
			;;
		-n|--number-only)
			OPTION_NUMBER_ONLY=1
			;;
		-s|--stable-only)
			OPTION_STABLE_ONLY=1
			;;
		-o|--order)
			OPTION_ORDER=1
			;;
		*)
			echo "Error! Unrecognized '${1}' as option or argument." >&2
			exit 2
			;;
	esac

	# Pop argument list, parses next argument on following iteration
	shift
done

list_latest_releases