diff --git a/blocksfree/legacy.py b/blocksfree/legacy.py
index 803fad4..dc3c7a1 100755
--- a/blocksfree/legacy.py
+++ b/blocksfree/legacy.py
@@ -776,10 +776,6 @@ def quit_now(exitcode=0):
 				shutil.rmtree('/tmp' + "/" + file)
 	sys.exit(exitcode)
 
-def usage(exitcode=1):
-	print(sys.modules[__name__].__doc__)
-	quit_now(exitcode)
-
 def to_sys_name(name):
 	if os.name == 'nt':
 		if name[-1] == '.':
@@ -1033,59 +1029,6 @@ def hexdump(
 
 
 def run_cppo(args: list):
-	while True: # breaks when there are no more arguments starting with dash
-		if len(args) == 1:
-			usage()
-
-		elif args[1][0] != '-':
-			break
-
-		elif args[1] == '-s':
-			g.afpsync_msg = False
-			args = args[1:]
-
-		elif args[1] == '-n':
-			g.extract_in_place = True
-			args = args[1:]
-
-		elif args[1] == '-uc':
-			g.casefold_upper = True
-			args = args[1:]
-
-		elif args[1] == '-ad':
-			g.use_appledouble = True
-			g.prodos_names = True
-			args = args[1:]
-
-		elif args[1] == '-shk':
-			g.src_shk = True
-			args = args[1:]
-
-		elif args[1] == '-pro':
-			g.prodos_names = True
-			args = args[1:]
-
-		elif args[1] == '-e':
-			g.use_extended = True
-			g.prodos_names = True
-			args = args[1:]
-
-		elif args[1] == '-cat':
-			g.catalog_only = True
-			args = args[1:]
-
-		else:
-			usage()
-
-	if g.use_appledouble and g.use_extended:
-		usage()
-	if g.catalog_only:
-		if len(args) != 2:
-			usage()
-	else:
-		if len(args) not in (3, 4):
-			usage()
-
 	try:
 		disk = Disk(args[1])
 	except IOError as e:
@@ -1279,7 +1222,9 @@ def run_cppo(args: list):
 	# enforce leading slash if ProDOS
 	if (not g.src_shk and not g.dos33 and g.extract_file
 			and (args[2][0] not in ('/', ':'))):
-		usage()
+		log.critical("Cannot extract {} from {}: "
+				"ProDOS volume name required".format(args[2], args[1]))
+		quit_now(2)
 
 	if g.dos33:
 		disk_name = (disk.diskname
diff --git a/cppo b/cppo
new file mode 100755
index 0000000..8ab1b93
--- /dev/null
+++ b/cppo
@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+# vim: set tabstop=4 shiftwidth=4 noexpandtab filetype=python:
+
+# Copyright (C) 2013-2016  Ivan Drucker
+# Copyright (C) 2017       T. Joseph Carter
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation; either version 2 of the License, or (at your
+# option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+# for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+#
+#
+# If interested, please see the file HISTORY.md for information about both the
+# technical and licensing decisions that have gone into the rewriting of cppo.
+
+"""cppo: Copy/catalog files from a ProDOS/DOS 3.3/ShrinkIt image/archive.
+
+copy all files: cppo [options] imagefile target_directory
+copy one file : cppo [options] imagefile /extract/path target_path
+catalog image : cppo -cat [options] imagefile
+
+options:
+-shk: ShrinkIt archive as source (also auto-enabled by filename).
+-ad : Netatalk-compatible AppleDouble metadata files and resource forks.
+-e  : Nulib2-compatible filenames with type/auxtype and resource forks.
+-uc : Copy GS/OS mixed case filenames as uppercase.
+-pro: Adapt DOS 3.3 names to ProDOS and remove addr/len from file data.
+
+/extract/path examples:
+    /FULL/PRODOS/PATH (ProDOS image source)
+    "MY FILENAME" (DOS 3.3 image source)
+    Dir:SubDir:FileName (ShrinkIt archive source)
+
++ after a file name indicates a GS/OS or Mac OS extended (forked) file.
+Wildcard matching (*) is not supported and images are not validated.
+ShrinkIt support requires Nulib2. cppo requires Python 2.6+ or 3.0+."""
+
+import sys
+
+from blocksfree.legacy import g
+import blocksfree.legacy
+
+def usage(exitcode=1):
+	print(sys.modules[__name__].__doc__)
+	sys.exit(exitcode)
+
+def cppo(args: list):
+	while True: # breaks when there are no more arguments starting with dash
+		if len(args) == 1:
+			usage()
+
+		elif args[1][0] != '-':
+			break
+
+		elif args[1] == '-s':
+			g.afpsync_msg = False
+			args = args[1:]
+
+		elif args[1] == '-n':
+			g.extract_in_place = True
+			args = args[1:]
+
+		elif args[1] == '-uc':
+			g.casefold_upper = True
+			args = args[1:]
+
+		elif args[1] == '-ad':
+			g.use_appledouble = True
+			g.prodos_names = True
+			args = args[1:]
+
+		elif args[1] == '-shk':
+			g.src_shk = True
+			args = args[1:]
+
+		elif args[1] == '-pro':
+			g.prodos_names = True
+			args = args[1:]
+
+		elif args[1] == '-e':
+			g.use_extended = True
+			g.prodos_names = True
+			args = args[1:]
+
+		elif args[1] == '-cat':
+			g.catalog_only = True
+			args = args[1:]
+
+		else:
+			usage()
+
+	blocksfree.legacy.run_cppo(args)
+
+if __name__ == '__main__':
+	cppo(sys.argv)