diff --git a/sosar.py b/sosar.py
index 1c0bd9e..7a57cdc 100755
--- a/sosar.py
+++ b/sosar.py
@@ -14,8 +14,39 @@ def cmd_mkfs(args, disk):
     print('XXX mkfs')
 
 
+def cmd_extract(args, disk):
+    for sf in disk.files(path = '', recursive = True):
+        name = sf.get_name()
+        #print(name)
+        #print(len(name))
+        eof = sf.get_eof()
+        data = sf.read(0, eof)
+        #print(len(data))
+        with open(name, 'wb') as f:
+            f.write(data)
+        break # XXX for debug, only extract first file
+
+
 parser = argparse.ArgumentParser()
 
+fmt_group = parser.add_mutually_exclusive_group()
+
+fmt_group.add_argument('--do',
+                       dest = 'format',
+                       action = 'store_const',
+                       const = 'do',
+                       help = "image in DOS sector order")
+
+fmt_group.add_argument('--po',
+                       dest = 'format',
+                       action = 'store_const',
+                       const = 'po',
+                       help = "image in SOS/ProDOS sector order")
+
+parser.add_argument('image',
+                    type = str,
+                    help = "SOS/ProDOS disk image")
+
 subparsers = parser.add_subparsers(title = 'commands',
                                    dest = 'cmd')
 
@@ -40,23 +71,19 @@ mkfs_parser.add_argument('--size',
                          default = 280,
                          help = 'filesystem size in blocks')
 
-parser.add_argument('image',
-                    type = str,
-                    help = "SOS/ProDOS disk image")
+extract_parser = subparsers.add_parser('x',
+                                       help = 'extract file(s)')
+extract_parser.set_defaults(cmd_fn = cmd_extract)
 
-fmt_group = parser.add_mutually_exclusive_group()
+extract_parser.add_argument('-r', '--recursive',
+                       action = 'store_true',
+                       help = 'recursively extract subdirectory content')
 
-fmt_group.add_argument('--do',
-                       dest = 'format',
-                       action = 'store_const',
-                       const = 'do',
-                       help = "image in DOS sector order")
-
-fmt_group.add_argument('--po',
-                       dest = 'format',
-                       action = 'store_const',
-                       const = 'po',
-                       help = "image in SOS/ProDOS sector order")
+extract_parser.add_argument('filename',
+                            type = str,
+                            nargs = '+',
+                            help = 'filename(s) to extract',
+)
 
 args = parser.parse_args()
 #print(args)
@@ -72,7 +99,8 @@ else:
     sys.exit(2)
 
 file_mode = { 'mkfs': 'w',
-              'ls': 'r' } [args.cmd] + 'b'
+              'ls': 'r',
+              'x': 'r' } [args.cmd] + 'b'
 
 image = open(args.image, file_mode)
 
diff --git a/sosdisk.py b/sosdisk.py
index f09e7e6..eeac0b5 100644
--- a/sosdisk.py
+++ b/sosdisk.py
@@ -124,7 +124,7 @@ sos_valid_fn_chars = set(string.ascii_uppercase + string.digits + '.')
 def bytes_to_sos_filename(l, b):
     assert len(b) == 15
     assert 1 <= l <= 15
-    s = str(b, 'ascii')
+    s = str(b[:l], 'ascii')
     assert all(c in sos_valid_fn_chars for c in s[:l])
     assert all(c == 0 for c in b[l:])
     return s.lower()
@@ -213,6 +213,21 @@ class SOSStorage:
     def is_sparse(self):
         return self.data_blocks != (self.last_block_index + 1)
 
+    def read(self,
+             offset = 0,
+             length = 0):
+        data = bytearray(length)
+        while length > 0:
+            block_index = offset // self.disk.block_size
+            block_offset = offset % self.disk.block_size
+            chunk_length = min(length, self.disk.block_size - block_offset)
+            if block_index in self.index:
+                block_number = self.index[block_index]
+                data[offset:offset+chunk_length] = self.disk.get_blocks(block_number)[block_offset:block_offset+chunk_length]
+            offset += chunk_length
+            length -= chunk_length
+        return data
+
 
 class SOSSeedling(SOSStorage):
     def __init__(self, disk, key_pointer):
@@ -271,7 +286,12 @@ class SOSDirectoryEntry:
         pass
 
 
-class SOSVolumeDirectoryHeader(SOSDirectoryEntry):
+class SOSDirectoryHeader(SOSDirectoryEntry):
+    def __init__(self, disk):
+        super().__init__(disk)
+
+
+class SOSVolumeDirectoryHeader(SOSDirectoryHeader):
     def __init__(self, disk, entry_data):
         super().__init__(disk)
         (storage_nl, name_b, self.reserved, creation_b, self.version, self.min_version, self.access, self.entry_length, self.entries_per_block, self.file_count, self.bitmap_pointer, self.total_blocks) = struct.unpack('<B15s8sLBBBBBHHH', entry_data)
@@ -286,7 +306,7 @@ class SOSVolumeDirectoryHeader(SOSDirectoryEntry):
         assert self.total_blocks == disk.block_count
         self.creation = u32_to_sos_timestamp(creation_b)
 
-class SOSSubdirectoryHeader(SOSDirectoryEntry):
+class SOSSubdirectoryHeader(SOSDirectoryHeader):
     def __init__(self, disk, entry_data):
         super().__init__(disk)
         (storage_nl, name_b, self.reserved, creation_b, self.version, self.min_version, self.access, self.entry_length, self.entries_per_block, self.file_count, self.bitmap_pointer, self.total_blocks) = struct.unpack('<B15s8sLBBBBBHHH', entry_data)
@@ -320,6 +340,20 @@ class SOSFileEntry(SOSDirectoryEntry):
             self.storage = SOSStorage.create(self.disk, self.storage_type, self.key_pointer)
 
 
+    def get_name(self):
+        return self.name
+
+
+    def get_eof(self):
+        return self.eof
+
+
+    def read(self,
+             offset = 0,
+             length = None):
+        return self.storage.read(offset, length)
+
+
     def print(self,
               prefix,
               recursive = False,
@@ -424,6 +458,13 @@ class SOSDirectory:
             else:
                 block_num = first_block + i
             
+    def files(self,
+              path,
+              recursive = False):
+        for db in self.directory_blocks:
+            for entry in db.entries:
+                if isinstance(entry, SOSFileEntry) and (entry.storage_type != StorageType.unused_entry) and hasattr(entry, 'storage'):
+                    yield entry
 
     def print(self, prefix,
               recursive = False,
@@ -492,6 +533,11 @@ class SOSDisk:
         length = count * 512
         return memoryview(self.data)[offset:offset+length]
 
+    def files(self,
+              path,
+              recursive = True):
+        return self.volume_directory.files(path, recursive)
+
     def print_directory(self,
                         recursive = False,
                         long = False,