scripts: Add aklite CLI example script (#7)

Signed-off-by: Andre Detsch <andre.detsch@foundries.io>

scripts/aklite-cli-example.sh

@@ -0,0 +1,67 @@
+#!/bin/env bash
+
+#
+# Aktualizr-lite command line interface usage example script
+#
+# Copyright (C) 2024 Foundries.io
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+
+# Relevant aktualizr-lite CLI return codes for controlling execution flow
+OK=0
+CHECKIN_OK_CACHED=3
+
+UPDATE_NEW_VERSION=16
+UPDATE_SYNC_APPS=17
+UPDATE_ROLLBACK=18
+
+REBOOT_REQUIRED_BOOT_FW=90
+REBOOT_REQUIRED_ROOT=100
+
+# Commands
+reboot_cmd="/sbin/reboot"
+aklite_cmd="/bin/aktualizr-lite"
+
+# Interval between each update server polling (seconds)
+interval=60
+
+# Complete previous installation, if pending
+$aklite_cmd run; ret=$?
+if [ $ret -eq $REBOOT_REQUIRED_ROOT ]; then
+    echo "A system reboot is required to finalize the pending installation."
+    exit 1
+fi
+
+while true; do
+    echo "Checking for updates..."
+    $aklite_cmd check; ret=$?
+    if [ $ret -eq $UPDATE_NEW_VERSION -o $ret -eq $UPDATE_SYNC_APPS -o $ret -eq $UPDATE_ROLLBACK ]; then
+        echo "There is a target that is meant to be installed (check returned $ret). Pulling..."
+        $aklite_cmd pull; ret=$?
+        if [ $ret -eq $OK ]; then
+            echo "Pull operation successful. Installing..."
+            $aklite_cmd install; ret=$?
+            if [ $ret -eq $REBOOT_REQUIRED_ROOT -o $ret -eq $REBOOT_REQUIRED_BOOT_FW ]; then
+                echo "Installation completed, reboot required ($ret)"
+                break
+            elif [ $ret -eq $OK ]; then
+                echo "Installation completed, no reboot needed"
+                continue
+            else
+                echo "Installation failed with error $ret"
+            fi
+        else
+            echo "Pull operation failed with error $ret"
+        fi
+    elif [ $ret -eq $OK -o $ret -eq $CHECKIN_OK_CACHED ]; then
+        echo "No update is needed"
+    else
+        echo "Check operation failed with error $ret"
+    fi
+    echo "Sleeping $interval seconds..."
+    sleep $interval
+done
+
+echo "Rebooting ($reboot_cmd)..."
+$reboot_cmd