irccat: handle bad options a little more gently

irccat

@@ -1,9 +1,7 @@
 #!/usr/bin/env python
 
 usage = """
-Send data to IRC channel
-
-usage: irccat [-s] <host> <port> <section> <text...>
+Usage: irccat [-s] <host> <port> <section> <text...>
 
 host:    supybot host running irccat plugin.
 port     The port irccat plugin listen to.
@@ -24,6 +22,13 @@ import os
 import sys
 import socket
 
+
+def error(why):
+    print "Error: " + why
+    print "Use -h for help"
+    sys.exit(1)
+
+
 sys.argv.pop(0)
 try:
     if sys.argv[0] == '-h' or sys.argv[0] == '--help':
@@ -35,18 +40,17 @@ try:
     elif 'IRCCAT_PASSWORD' in os.environ:
         pw = os.environ['IRCCAT_PASSWORD']
     else:
-        print usage
-        sys.exit(1)
+        error("neither -s nor IRCCAT_PASSWORD present.")
     host = sys.argv.pop(0)
     port = int(sys.argv.pop(0))
     section = sys.argv.pop(0)
-except (IndexError, ValueError):
-    print usage
-    sys.exit(1)
+except ValueError:
+    error("illegal port number.")
+except IndexError:
+    error("too few arguments.")
 text = ' '.join(sys.argv)
 if not text:
-    print usage
-    sys.exit(1)
+    error("too few arguments.")
 
 s = socket.create_connection((host, port))
 s.send('%s;%s;%s\n' % (section, pw, text))