finish the research for python-subprocess

 #!/usr/bin/python
 # -*- coding: utf-8 -*-
-
-import sys, shlex, time, subprocess
-
-cmd = "./python.subprocess 0 800"
-args = shlex.split(str(cmd))
-print "cmd: %s, args: %s"%(cmd, args)
-
-def use_communicate(args, fout, ferr):
-    process = subprocess.Popen(args, stdout=fout, stderr=ferr)
+
+import sys, shlex, time, subprocess
+
+cmd = "./python.subprocess 0 80000"
+args = shlex.split(str(cmd))
+print "cmd: %s, args: %s"%(cmd, args)
+
+# the communicate will read all data and wait for sub process to quit.
+def use_communicate(args, fout, ferr):
+    process = subprocess.Popen(args, stdout=fout, stderr=ferr)
     (stdout_str, stderr_str) = process.communicate()
     return (stdout_str, stderr_str)
 
+# if use subprocess.PIPE, the pipe will full about 50KB data,
+# and sub process will blocked, then timeout will kill it.
 def use_poll(args, fout, ferr, timeout):
     (stdout_str, stderr_str) = (None, None)
     process = subprocess.Popen(args, stdout=fout, stderr=ferr)
@@ -28,27 +31,22 @@ def use_poll(args, fout, ferr, timeout):
         time.sleep(1)
     process.wait()
     return (stdout_str, stderr_str)
-def use_communicate_timeout(args, fout, ferr, timeout):
-    (stdout_str, stderr_str) = (None, None)
-    process = subprocess.Popen(args, stdout=fout, stderr=ferr)
-    starttime = time.time()
-    while True:
 
-fnull = open("/dev/null", "rw")
-fout = subprocess.PIPE#fnull.fileno()
-ferr = subprocess.PIPE#fnull#fnull.fileno()
-print "fout=%s, ferr=%s"%(fout, ferr)
+# stdout/stderr can be fd, fileobject, subprocess.PIPE, None
+fnull = open("/dev/null", "rw")
+fout = fnull.fileno()#subprocess.PIPE#fnull#fnull.fileno()
+ferr = fnull.fileno()#subprocess.PIPE#fnull#fnull.fileno()
+print "fout=%s, ferr=%s"%(fout, ferr)
 #(stdout_str, stderr_str) = use_communicate(args, fout, ferr)
-#(stdout_str, stderr_str) = use_poll(args, fout, ferr, 10)
-(stdout_str, stderr_str) = use_communicate_timeout(args, fout, ferr, 10)
+(stdout_str, stderr_str) = use_poll(args, fout, ferr, 10)
 
-def print_result(stdout_str, stderr_str):
-    if stdout_str is None:
-        stdout_str = ""
-    if stderr_str is None:
-        stderr_str = ""
+def print_result(stdout_str, stderr_str):
+    if stdout_str is None:
+        stdout_str = ""
+    if stderr_str is None:
+        stderr_str = ""
     print "terminated, size of stdout=%s, stderr=%s"%(len(stdout_str), len(stderr_str))
-    while True:
-        time.sleep(1)
+    while True:
+        time.sleep(1)
 
 print_result(stdout_str, stderr_str)