cslarsen · January 11, 2012 15:16 · Jan 11, 2012
diff --git a/ipv4.py b/ipv4.py
@@ -0,0 +1,46 @@
+#!/usr/bin/env python
+
+"""Functions to convert IPv4 address to integer and vice-versa.
+
+Written by Christian Stigen Larsen, http://csl.sublevel3.org
+Placed in the public domain by the author, 2012-01-11
+
+Example usage:
+$ ./ipv4 192.168.0.1 3232235521
+192.168.0.1 ==> 3232235521
+3232235521 ==> 192.168.0.1
+"""
+
+import sys
+
+def from_string(s):
+  "Convert dotted IPv4 address to integer."
+  return reduce(lambda a,b: a<<8 | b, map(int, s.split(".")))
+
+def to_string(ip):
+  "Convert 32-bit integer to dotted IPv4 address."
+  return ".".join(map(lambda n: str(ip>>n & 0xFF), [24,16,8,0]))
+
+if __name__ == "__main__":
+  if len(sys.argv) <= 1:
+    print "Usage: ipv4 [ (address | integer)* ]"
+    print "Converts between IPv4 addresses and integers."
+    print ""
+    print "Example usage:"
+    print "$ ./ipv4 192.168.0.1 3232235521"
+    print "192.168.0.1 ==> 3232235521"
+    print "3232235521 ==> 192.168.0.1"
+    print ""
+    print "Written by Christian Stigen Larsen, http://csl.sublevel3.org"
+    print "Placed in the public domain by the author, 2012-01-11"
+    sys.exit(0)
+
+  for arg in sys.argv[1:]:
+    if arg.count(".") == 3:
+      print arg, "==>", from_string(arg)
+    else:
+      try:
+        print arg, "==>", to_string(int(arg))
+      except Exception, e:
+        print "Not an integer or dotted IPv4 address:", arg
+        sys.exit(1)