buildroot

#!/usr/bin/env bash

​

# This script is a wrapper to the other download backends.

# Its role is to ensure atomicity when saving downloaded files

# back to BR2_DL_DIR, and not clutter BR2_DL_DIR with partial,

# failed downloads.

#

# Call it with -h to see some help.

​

# To avoid cluttering BR2_DL_DIR, we download to a trashable

# location, namely in $(BUILD_DIR).

# Then, we move the downloaded file to a temporary file in the

# same directory as the final output file.

# This allows us to finally atomically rename it to its final

# name.

# If anything goes wrong, we just remove all the temporaries

# created so far.

​

# We want to catch any unexpected failure, and exit immediately.

set -e

​

main() {

    local OPT OPTARG

    local backend output

​

    # Parse our options; anything after '--' is for the backend

    while getopts :hb:o: OPT; do

        case "${OPT}" in

        h)  help; exit 0;;

        b)  backend="${OPTARG}";;

        o)  output="${OPTARG}";;

        :)  error "option '%s' expects a mandatory argument\n" "${OPTARG}";;

        \?) error "unknown option '%s'\n" "${OPTARG}";;

        esac

    done

    # Forget our options, and keep only those for the backend

    shift $((OPTIND-1))

​

    if [ -z "${backend}" ]; then

        error "no backend specified, use -b\n"

    fi

    if [ -z "${output}" ]; then

        error "no output specified, use -o\n"

    fi

​

    # tmpd is a temporary directory in which backends may store intermediate

    # by-products of the download.

    # tmpf is the file in which the backends should put the downloaded content.

    # tmpd is located in $(BUILD_DIR), so as not to clutter the (precious)

    # $(BR2_DL_DIR)

    # We let the backends create tmpf, so they are able to set whatever

    # permission bits they want (although we're only really interested in

    # the executable bit.)

    tmpd="$(mktemp -d "${BUILD_DIR}/.${output##*/}.XXXXXX")"

    tmpf="${tmpd}/output"

​

    # Helpers expect to run in a directory that is *really* trashable, so

    # they are free to create whatever files and/or sub-dirs they might need.

    # Doing the 'cd' here rather than in all backends is easier.

    cd "${tmpd}"

​

    # If the backend fails, we can just remove the temporary directory to

    # remove all the cruft it may have left behind. Then we just exit in