Implement system exit code on error

zoom_dl/__init__.py

@@ -17,3 +17,5 @@ def main():
     all_urls = [args.url]  # prepare for batch reading
     zdl = ZoomDL(args)
     zdl.download(all_urls)
+
+    sys.exit(zdl.exit_code)

zoom_dl/zoomdl.py

@@ -26,6 +26,7 @@ def __init__(self, args):
         self.url, self.domain, self.subdomain = "", "", ""
         self.metadata = None
         self.session = requests.session()
+        self.exit_code = 0
 
         self.loglevel = self.args.log_level
 
@@ -69,6 +70,11 @@ def _print(self, message, level=0):
         if level < 5 and level >= self.loglevel:
             print(message)
 
+        """Set system exit code to 1 if zoomdl encounters a (critical) error."""
+        # there is potential here for more granular exit codes if desired
+        if level < 5 and level >= 3:
+            self.exit_code = 1
+
     def _change_page(self, url):
         """Change page, with side methods."""
         self._print("Changing page to {}".format(url), 0)