Add -d/--dry-run options

stechuhr_server/retention.py

 #!/usr/bin/env python 
 #-*- coding: utf-8 -*-
-import re, os
+import re, os, sys
 import datetime as dt
 import sqlite3
 import logging
@@ -61,11 +61,36 @@ def delete_older(conn, config, logger, dry_run=True):
 
 
 
+
 def data_retention():
     # Start logging
     logger = logging.getLogger(__name__)
     logger.info('Starting data_retention() in {}'.format(APPLICATION_NAME))
 
+    # Add dry run options
+    dry = ["-d", "--dry-run"]
+
+    # Initially false (no dry-run)
+    dry_run = False
+
+    # At the time only one argument is supported, display error otherwise
+    if len(sys.argv) == 2:
+        # If -d or --dry-run is present, activate the flag, display in log
+        if sys.argv[1] in dry:
+            dry_run = True
+            logger.warning("Running in Dry-Run-Mode (listing to-be-deleted entries, but not actually deleting anything)")
+        else:
+            if not sys.argv[1] in ["-h", "--help"]:
+                logger.error("Argument \"{}\" is not supported".format(sys.argv[1]))
+            else:
+                logger.info("stechuhr-server data retention script.")
+            logger.info("Possible options are: {}".format(dry))
+            exit()
+    elif len(sys.argv) > 2:
+        logger.error("Arguments {} ar not supported".format(", ".join(sys.argv[1:])))
+        logger.info("Possible options are: {}".format(dry))
+        exit()
+
     # Initialize the configuration (create a default one if needed)
     config = initialize_config(logger)
     logger.info('Will delete entries older than {} days (as set in config)'.format(config["retention"]["duration"]))
@@ -74,7 +99,7 @@ def data_retention():
     conn = initialize_db(config, logger)
 
     # Delete data older than the time specified in the config
-    delete_older(conn, config, logger, dry_run=False)
+    delete_older(conn, config, logger, dry_run=dry_run)
 
     logger.info("Exiting.")