minimal snap client

sc

#!/bin/bash

# naive snap replacement

set -ex

SNAPD_SOCKET=/run/snapd.socket
CURL="${CURL:-curl}"
CURL_CMD="${CURL} --unix-socket $SNAPD_SOCKET -D- -v"

if [[ "$0" == /snap/bin/* ]] || [[ "$0" == /var/lib/snapd/snap/bin/* ]]; then
    exec "$(readlink -f "$0")" run "$(basename "$0")" "$@"
fi

cmd="$1"
if [ -z "$cmd" ]; then
    echo "error: sc <install|remove|list> [--purge] [--dangerous] [<snap-name>|<snap-file>]"
    exit 1
fi

case "$cmd" in
    remove)
        shift
        purge="false"
        if [ "$1" = "--purge" ]; then
            purge="true"
            shift 1
        fi
        name="$1"
        if [ -z "$name" ]; then
            echo "error: missing snap name"
            exit 1
        fi
        echo "{\"action\":\"$cmd\",\"purge\": $purge}" | $CURL_CMD \
                                           -X POST -d@- "http://localhost/v2/snaps/$name"
        ;;
    install)
        shift
        dangerous="false"
        if [ "$1" = "--dangerous" ]; then
            dangerous="true"
            shift
        fi
        name="$1"
        if [ -z "$name" ]; then
            echo "error: missing snap name"
            exit 1
        fi
        if [ "${name%.snap}" != "$name" ]; then
            # file upload
            $CURL -F action=install -F "dangerous=$dangerous" -F "snap=@$name" \
                  -X POST "http://localhost/v2/snaps"
        else
            echo "{\"action\":\"$cmd\",\"dangerous\":\"$dangerous\"}" | $CURL_CMD \
                                                                 -X POST -d@- "http://localhost/v2/snaps/$name"
        fi
        ;;
    list)
        $CURL_CMD "http://localhost/v2/snaps"
        exit 0
        ;;
    change)
        shift
        nr="$1"
        if [ -z "$nr" ]; then
           echo "error: missing change ID"
           exit 1
        fi
        $CURL_CMD "http://localhost/v2/changes/$nr" | tr '[]{}' '\n'
        ;;
    run)
        real=/usr/bin/snap.real
        for arg in "$@"; do
            case "$arg" in
                --hook*|--timer*|--shell|--help|--command*)
                    exec "$real" "$@"
                    # noreturn
                    ;;
            esac
        done
        # drop "run"
        shift

        snapapp="$1"
        shift
        if [[ "${snapapp/.*/}" = "$snapapp" ]]; then
            snapapp="$snapapp.$snapapp"
        fi
        SNAP_NAME=${snapapp/.*/}
        SNAP_REVISION="$(basename "$(readlink "/snap/${SNAP_NAME}/current")")"
        SNAP=/snap/$SNAP_NAME/$SNAP_REVISION
        SNAP_COMMON=/var/snap/$SNAP
        SNAP_DATA=/var/snap/$SNAP_REVISION
        SNAP_INSTANCE_NAME=$SNAP_NAME
        SNAP_INSTANCE_KEY=
        SNAP_VERSION=123
        needsbase="$(awk '/^base: .*/ {print $2}' < "$SNAP/meta/snap.yaml")"
        basearg=
        if [ -n "$needsbase" ]; then
            basearg="--base $needsbase"
        fi
        export SNAP SNAP_REVISION \
               SNAP_DATA SNAP_COMMON \
               SNAP_NAME SNAP_INSTANCE_NAME SNAP_INSTANCE_KEY \
               SNAP_VERSION
        #shellcheck disable=SC2086
        exec /usr/lib/snapd/snap-confine $basearg "snap.$snapapp" /usr/lib/snapd/snap-exec "$snapapp" "$@"
        ;;
esac