cros-safe-copy: sync and sleep seem useless

cros-safe-copy.py

 #!/usr/bin/env python2
 # -*- coding: utf-8 -*-
 """
-Usage: python cros-safe-copy.py SRC DST [SLEEP]
+Usage: python cros-safe-copy.py SRC DST
 
 Where SRC is the source file path
       DST is the destination file path
-      SLEEP is the time to wait between two copied chunk (in second)
 
 Do a copy of flushed everytime chunks from SRC to DST. This is usefull if your
-`dd` command makes your machine rebooting. More, this script save the state
-during copying so that even if the machine reboots, you can copy from where it
-was stopped. (Be careful to run your script where CWD is persistent! Avoid /tmp
-or ~/Downloads on Chromebooks!)
+`dd` command makes your machine rebooting.
 
 Example:
   sudo python cros-safe-copy.py NayuOS.img /dev/sda
-  # savestate.json file is saved in CWD
 """
 
-import sys, os, time, json
+import sys, os
+KiB = 1024
+MiB = 1024*KiB
 
 input = sys.argv[1]
 output = sys.argv[2]
-sleep = int(sys.argv[3]) if len(sys.argv) > 3 else 0
-
-def saveState(d):
-  open("savestate.json.lock", "wx").write(json.dumps(d))
-  os.rename("savestate.json.lock", "savestate.json")
-
-def loadState():
-  try:
-    state = json.loads(open("savestate.json").read())
-    print "Using savestate.json"
-    return state
-  except IOError:
-    print "Creating savestate.json"
-    MiB = 1024*1024
-    bs = 65536
-    saveState(dict(
-      input=input,
-      output=output,
-      bs=bs,
-      count=50*MiB/bs,
-      skip=0,
-      seek=0,
-    ))
-    return loadState()
+bs = 64*KiB
+count = 50*MiB/bs
+skip = 0
 
 def quote(args):
   return " ".join(["'%s'" % a.replace("'", "'\\''") for a in args])
 
-state = loadState()
-assert state["input"] == input
-assert state["output"] == output
-
-while state["skip"] * state["bs"] < os.stat(input).st_size:
+while skip * bs < os.stat(input).st_size:
   command = quote([
     "dd",
-    "bs=%d" % state["bs"],
-    "count=%d" % state["count"],
-    "seek=%d" % state["seek"],
-    "skip=%d" % state["skip"],
+    "bs=%d" % bs,
+    "count=%d" % count,
+    "seek=%d" % skip,
+    "skip=%d" % skip,
     "if=%s" % input,
     "of=%s" % output,
   ])
   print "$", command
   if os.system(command):
-    break
-  print "$ sync"
-  if os.system("sync"):  # seems not useful
-    break
-  state["skip"] += state["count"]
-  state["seek"] += state["count"]
-  saveState(state)
-  if sleep > 0:
-    print "sleeping for %d second(s)" % sleep
-    time.sleep(sleep)
\ No newline at end of file
+    sys.exit(1)
+  skip += count