--- a/textshaper/indent.py	Sun Feb 23 10:14:06 2014 -0800
+++ b/textshaper/indent.py	Sun Feb 23 10:57:19 2014 -0800
@@ -4,7 +4,7 @@
 indentation of text blocks
 """
 
-import optparse
+import argparse
 import os
 import sys
 
@@ -42,33 +42,32 @@
     return retval
 
 
+def add_arguments(parser):
+    parser.add_argument('infile', nargs='?', type=argparse.FileType('r'),
+                        default=sys.stdin)
+    parser.add_argument('-o', '--output', dest='output',
+                        help="output file or stdout if not given")
+
 def main(args=sys.argv[1:]):
-    # TODO : refactor to be more general and stuff
 
     # parse command line
-    usage = '%prog [options] [file] [file2] [...]'
     description = """indent files or stdin if no files given"""
-    parser = optparse.OptionParser(usage=usage, description=__doc__)
-    parser.add_option('-o', '--output', dest='output',
-                      help="output file or stdout if not given")
-    options, files = parser.parse_args(args)
-
-    # input from files or stdin
-    if files:
-        missing = [not os.path.exists(filename) for filename in files]
-        if missing:
-            parser.error("File(s) not found: %s" % ', '.join(missing))
-        def _files():
-            for filename in files:
-                with open(f, 'r') as f:
-                    yield f
-    else:
-        def _files():
-            yield sys.stdin
+    parser = argparse.Argument(description=__doc__)
+    add_arguments(parser)
+    options = parser.parse_args(args)
 
     # process input
     for f in _files():
-        print f
+
+        # indent the text
+        indented = indent(f)
+
+        # append to output
+        if options.output:
+            with open(options.output, 'a') as f:
+                f.write(indented)
+        else:
+            sys.stdout.write(indented)
 
 if __name__ == '__main__':
     main()