Creates a Gradle wrapper in $PWD for the latest Gradle version (optionally, latest for the given major version, e.g. `./create-gradle-wrapper.bash 4` will fetch the latest Gradle 4.X wrapper).

create-gradle-wrapper.bash

#!/usr/bin/env bash

set -o errexit -o errtrace -o noclobber -o nounset -o pipefail

trap 'e=$?; if [ "$e" -ne "0" ]; then printf "LINE %s: exit %s <- %s%s\\n" "$BASH_LINENO" "$e" "${BASH_COMMAND}" "$(printf " <- %s" "${FUNCNAME[@]:-main}")" 1>&2; fi' EXIT

PROGNAME="${0##*/}"


contains_value() {
	local value
	value="$1"
	shift
	for arg in "$@"; do
		if [ "$value" == "$arg" ]; then
			return 0
		fi
	done
	return 1
}

get_versions() {
	local all_versions_data
	local versions
	all_versions_data="$(curl -s https://services.gradle.org/versions/all)"
	versions="$(printf '%s' "${all_versions_data}" | \
		jq -r 'map(select([.snapshot, .nightly, .releaseNightly, .activeRc, .broken, (.rcFor != ""), (.milestoneFor != ""), (.version | test("milestone|rc"; "i")) | not] | all) | .version) | join("\n")' | sort -V)"
	printf '%s\n' "${versions}"
}

get_latest_version() {
	local selected_version
	local versions

	versions="$(get_versions | sort -rV)"
	if [[ $# -eq 1 ]]; then
		versions="$(printf '%s\n' "$versions" | grep -E "^$1(\..+)?$")"
		selected_version="$(printf '%s\n' "$versions" | head -n 1)"
	else
		selected_version="$(curl -s 'https://services.gradle.org/versions/current' | jq -r '.version')"
	fi
	1>&2 printf 'selected version: %s\n' "$selected_version"
	1>&2 printf 'available versions:\n%s\n' "$versions"
	printf '%s\n' "$selected_version"
}

usage() {
	>&2 cat <<EOF
NAME
	${PROGNAME} -- Utility to create a Gradle wrapper for the latest release of Gradle.

SYNOPSIS
	${PROGNAME} [-h] -l [<MAJOR VERSION>[.<MINOR VERSION>]]

DESCRIPTION
	${PROGNAME} is a utility to create a Gradle wrapper for the latest release of Gradle,
	with latest version optionally filtered for the major or minor release version if provided.

	The options are as follows:

	-h	print this help and exit

	-l	list matching version without creating Gradle wrapper

EXAMPLES
	Create a wrapper for the latest Gradle release version:
	>>> ${PROGNAME}

	Alternatively, you can print the latest Gradle release version without creating a wrapper:
	>>> ${PROGNAME} -l

	Or you can get the latest 6.X release with:
	>>> ${PROGNAME} -l 6

	You can also specify the minor version, too:
	>>> ${PROGNAME} -l 7.1
EOF
}

LIST_ONLY=""

# options which must be given
REQUIRED_OPTS=()
# tracks which options have been provided
PROVIDED_OPTS=()
# options which may be given more than once
ADDITIVE_OPTS=()
# minimum number of positional arguments allowed (ignored if empty)
MIN_POSITIONAL_ARGS=""
# maximum number of positional arguments allowed (ignored if empty)
MAX_POSITIONAL_ARGS="1"
while getopts 'hl' opt; do
	if ! contains_value "$opt" "${ADDITIVE_OPTS[@]:-}" && contains_value "$opt" "${PROVIDED_OPTS[@]:-}"; then
		>&2 printf '%s: option cannot be given more than once -- %s\n' "$0" "$opt"
		usage
		exit 1
	fi

	case "$opt" in
		h)
			usage
			exit 0
			;;
		l)
			LIST_ONLY="y"
			;;
		*)
			usage
			exit 1
			;;
	esac
	PROVIDED_OPTS+=("$opt")
done
shift $((OPTIND - 1))
if [ -n "$MIN_POSITIONAL_ARGS" ] && [ "$#" -lt "$MIN_POSITIONAL_ARGS" ]; then
	>&2 printf '%s: at least %d positional argument(s) are needed but got %d -- %s\n' "$0" "$MIN_POSITIONAL_ARGS" "$#" "$(printf "'%s' " "$@")"
	usage
	exit 1
fi
if [ -n "$MAX_POSITIONAL_ARGS" ] && [ "$#" -gt "$MAX_POSITIONAL_ARGS" ]; then
	>&2 printf '%s: up to %d positional argument(s) are allowed but got %d -- %s\n' "$0" "$MAX_POSITIONAL_ARGS" "$#" "$(printf "'%s' " "$@")"
	usage
	exit 1
fi

MISSING_OPTS=()
if [ "${#REQUIRED_OPTS[@]}" -gt "0" ]; then
	for opt in "${REQUIRED_OPTS[@]}"; do
		if ! contains_value "$opt" "${PROVIDED_OPTS[@]:-}"; then
			MISSING_OPTS+=("${opt}")
		fi
	done
	if [ "${#MISSING_OPTS[@]}" -gt "0" ]; then
		>&2 printf '%s: missing required options -- %s\n' "$0" "${MISSING_OPTS[*]}"
		usage
		exit 1
	fi
fi

GRADLE_VERSION="$(get_latest_version "$@")"
printf 'using Gradle %s (see https://gradle.org/releases/)\n' "${GRADLE_VERSION}"

if [ -z "${LIST_ONLY}" ]; then
	TMP_DIR="$(mktemp -d "${0##*/}.XXXXXX")" || exit 1
	printf 'TMP_DIR: %s\n' "${TMP_DIR}" 1>&2
	for fpath in "build.gradle" "settings.gradle" "buildSrc"; do
		if [ -e "$fpath" ]; then
			mv -v "$fpath" "$TMP_DIR/$fpath.bak"
		fi
	done
	printf "rootProject.name = '$(basename "$(pwd)")'\n" > "settings.gradle"
	gradle --info --full-stacktrace --no-daemon --no-watch-fs wrapper --gradle-version "${GRADLE_VERSION}" --distribution-type all
	for fpath in "build.gradle" "settings.gradle" "buildSrc"; do
		if [ -e "$TMP_DIR/$fpath.bak" ]; then
			mv -vf "$TMP_DIR/$fpath.bak" "$fpath"
		fi
	done
	rm -vfr "${TMP_DIR}"
fi