From 818a7f807eb594f1822a376108f4682f540eb0ca Mon Sep 17 00:00:00 2001
From: Scott Kitterman <scott@kitterman.com>
Date: Sun, 4 Jun 2017 17:05:18 -0400
Subject: [PATCH]     - Port dkimsign.py to use argparse; now gives standard
 usage message and       is more extensible

---
 ChangeLog   |  3 ++-
 README      |  3 ++-
 dkimsign.py | 23 +++++++++++------------
 3 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 1f40d88..e61bfac 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,6 @@
 UNRELEASED Version 0.7.0
-    - 
+    - Port dkimsign.py to use argparse; now gives standard usage message and
+      is more extensible
 
 2017-05-30 Version 0.6.2
     - Fixed problem with header folding that caused the first line to be
diff --git a/README b/README
index 1807c39..3047946 100644
--- a/README
+++ b/README
@@ -11,7 +11,7 @@ signing and verification.
 
 VERSION
 
-This is dkimpy 0.6.2.
+This is dkimpy 0.7.0.
 
 REQUIREMENTS
 
@@ -19,6 +19,7 @@ REQUIREMENTS
    tested on python < 2.7 or python3 < 3.4, but may still work on python2.6
    and python 3.1 - 3.3.
  - dnspython or pydns. dnspython is preferred if both are present.
+ - argparse.  Standard library in python2.7 and later.
 
 INSTALLATION
 
diff --git a/dkimsign.py b/dkimsign.py
index 9aff199..021029f 100644
--- a/dkimsign.py
+++ b/dkimsign.py
@@ -24,29 +24,28 @@
 from __future__ import print_function
 
 import sys
+import argparse
 
 import dkim
 
-if len(sys.argv) < 4 or len(sys.argv) > 5:
-    print("Usage: dkimsign.py selector domain privatekeyfile [identity]", file=sys.stderr)
-    sys.exit(1)
+# Backward compatibility hack because argparse doesn't support optional
+# positional arguments
+arguments=['--'+arg if arg[:8] == 'identity' else arg for arg in sys.argv[1:]]
+parser = argparse.ArgumentParser(description='Produce DKIM signature for email messages.')
+parser.add_argument('selector', action="store")
+parser.add_argument('domain', action="store")
+parser.add_argument('privatekeyfile', action="store")
+parser.add_argument('--identity', help='Optional value for i= tag.')
+args=parser.parse_args(arguments)
 
 if sys.version_info[0] >= 3:
     # Make sys.stdin and stdout binary streams.
     sys.stdin = sys.stdin.detach()
     sys.stdout = sys.stdout.detach()
 
-selector = sys.argv[1].encode('ascii')
-domain = sys.argv[2].encode('ascii')
-privatekeyfile = sys.argv[3]
-if len(sys.argv) > 5:
-    identity = sys.argv[4].encode('ascii')
-else:
-    identity = None
-
 message = sys.stdin.read()
 try:
-    sig = dkim.sign(message, selector, domain, open(privatekeyfile, "rb").read(), identity = identity)
+    sig = dkim.sign(message, args.selector, args.domain, open(args.privatekeyfile, "rb").read(), identity = args.identity)
     sys.stdout.write(sig)
     sys.stdout.write(message)
 except Exception as e: