Add release download script

README.md

@@ -106,6 +106,20 @@ extract it. Release assets are named
 The snippet below fetches the latest version automatically via the GitHub
 API, so you only need to set `ARCH`:
 
+For a reusable variant of the same process, download and run
+[`download-latest.sh`](packaging/download-latest.sh):
+
+```sh
+curl -fsSLO https://raw.githubusercontent.com/LarsLaskowski/PiMonitor/main/packaging/download-latest.sh
+chmod +x download-latest.sh
+./download-latest.sh
+```
+
+The script detects the architecture automatically (`aarch64` becomes `arm64`;
+32-bit Raspberry Pi OS becomes `armv6`), downloads and extracts the latest
+release, then lists its contents. To override the detection, run it with
+`ARCH=arm64 ./download-latest.sh` or `ARCH=armv6 ./download-latest.sh`.
+
 ```sh
 ARCH=arm64   # or armv6, see above
 

packaging/download-latest.sh

@@ -0,0 +1,82 @@
+#!/usr/bin/env bash
+# Download and unpack the latest PiMonitor release for a Raspberry Pi.
+#
+# Usage:
+#   ./download-latest.sh
+#   ARCH=arm64 ./download-latest.sh  # optional manual override
+
+set -euo pipefail
+
+readonly REPOSITORY='larslaskowski/pimonitor'
+# Restrict both the initial request and any redirect to HTTPS, so a
+# compromised or misconfigured server can't downgrade the download to plain
+# HTTP.
+readonly CURL=(curl -fsSL --proto '=https' --proto-redir '=https')
+
+if [[ -z "${ARCH:-}" ]]; then
+  case "$(uname -m)" in
+    aarch64|arm64)
+      ARCH='arm64'
+      ;;
+    armv6l|armv7l|armv8l)
+      # The armv6 binary also runs on newer 32-bit ARM Raspberry Pi OS.
+      ARCH='armv6'
+      ;;
+    *)
+      printf 'Could not determine a supported Raspberry Pi architecture from: %s\n' "$(uname -m)" >&2
+      printf 'Set ARCH manually to arm64 or armv6.\n' >&2
+      exit 2
+      ;;
+  esac
+fi
+
+case "${ARCH:-}" in
+  arm64|armv6)
+    ;;
+  *)
+    printf 'Unsupported ARCH %q; use arm64 or armv6.\n' "$ARCH" >&2
+    exit 2
+    ;;
+esac
+
+for command in curl tar; do
+  if ! command -v "$command" >/dev/null 2>&1; then
+    printf 'Required command not found: %s\n' "$command" >&2
+    exit 1
+  fi
+done
+
+version=$("${CURL[@]}" "https://api.github.com/repos/${REPOSITORY}/releases/latest" \
+  | awk -F '"' '/"tag_name"/ { print $4; exit }')
+
+if [[ -z "$version" ]]; then
+  printf 'Could not determine the latest PiMonitor release version.\n' >&2
+  exit 1
+fi
+
+archive="pimonitor_${version#v}_linux_${ARCH}.tar.gz"
+directory="${archive%.tar.gz}"
+url="https://github.com/${REPOSITORY}/releases/download/${version}/${archive}"
+
+if [[ -e "$directory" ]]; then
+  printf 'Target directory already exists: %s\n' "$directory" >&2
+  printf 'Remove it or run the script in another directory.\n' >&2
+  exit 1
+fi
+
+printf 'Downloading PiMonitor %s for %s ...\n' "$version" "$ARCH"
+"${CURL[@]}" -o "$archive" "$url"
+
+printf 'Extracting %s ...\n' "$archive"
+tar xzf "$archive"
+
+if [[ ! -d "$directory" ]]; then
+  printf 'Expected extracted directory not found: %s\n' "$directory" >&2
+  exit 1
+fi
+
+cd "$directory"
+ls
+
+printf '\nRelease extracted to %s\n' "$PWD"
+printf 'To continue, run: cd %q && sudo ./install.sh\n' "$PWD"