[Python-checkins] cpython (3.1): Issue #11459: A `bufsize` value of 0 in subprocess.Popen() really creates

Sat Mar 19 17:10:01 CET 2011

http://hg.python.org/cpython/rev/1dc52ecb8949
changeset: 68679:1dc52ecb8949
branch: 3.1
parent: 68659:c61b72b0650d
user: Antoine Pitrou <solipsis at pitrou.net>
date: Sat Mar 19 17:00:37 2011 +0100
summary:
 Issue #11459: A `bufsize` value of 0 in subprocess.Popen() really creates
unbuffered pipes, such that select() works properly on them.
files:
 Doc/library/platform.rst
 Lib/os.py
 Lib/platform.py
 Lib/subprocess.py
 Lib/test/test_subprocess.py
 Misc/NEWS

diff --git a/Doc/library/platform.rst b/Doc/library/platform.rst
--- a/Doc/library/platform.rst
+++ b/Doc/library/platform.rst
@@ -205,7 +205,7 @@
 Win95/98 specific
 ^^^^^^^^^^^^^^^^^
 
-.. function:: popen(cmd, mode='r', bufsize=None)
+.. function:: popen(cmd, mode='r', bufsize=-1)
 
 Portable :func:`popen` interface. Find a working popen implementation
 preferring :func:`win32pipe.popen`. On Windows NT, :func:`win32pipe.popen`
diff --git a/Lib/os.py b/Lib/os.py
--- a/Lib/os.py
+++ b/Lib/os.py
@@ -629,11 +629,13 @@
 return bs
 
 # Supply os.popen()
-def popen(cmd, mode="r", buffering=None):
+def popen(cmd, mode="r", buffering=-1):
 if not isinstance(cmd, str):
 raise TypeError("invalid cmd type (%s, expected string)" % type(cmd))
 if mode not in ("r", "w"):
 raise ValueError("invalid mode %r" % mode)
+ if buffering == 0 or buffering == None:
+ raise ValueError("popen() does not support unbuffered streams")
 import subprocess, io
 if mode == "r":
 proc = subprocess.Popen(cmd,
diff --git a/Lib/platform.py b/Lib/platform.py
--- a/Lib/platform.py
+++ b/Lib/platform.py
@@ -398,7 +398,7 @@
 # Alias
 __del__ = close
 
-def popen(cmd, mode='r', bufsize=None):
+def popen(cmd, mode='r', bufsize=-1):
 
 """ Portable popen() interface.
 """
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -653,8 +653,6 @@
 if errread is not None:
 errread = msvcrt.open_osfhandle(errread.Detach(), 0)
 
- if bufsize == 0:
- bufsize = 1 # Nearly unbuffered (XXX for now)
 if p2cwrite is not None:
 self.stdin = io.open(p2cwrite, 'wb', bufsize)
 if self.universal_newlines:
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -864,6 +864,21 @@
 def prepare():
 raise ValueError("surrogate:\uDCff")
 
+ def test_select_unbuffered(self):
+ # Issue #11459: bufsize=0 should really set the pipes as
+ # unbuffered (and therefore let select() work properly).
+ select = support.import_module("select")
+ p = subprocess.Popen([sys.executable, "-c",
+ 'import sys;'
+ 'sys.stdout.write("apple")'],
+ stdout=subprocess.PIPE,
+ bufsize=0)
+ f = p.stdout
+ try:
+ self.assertEqual(f.read(4), b"appl")
+ self.assertIn(f, select.select([f], [], [], 0.0)[0])
+ finally:
+ p.wait()
 
 #
 # Windows tests
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -40,6 +40,9 @@
 Library
 -------
 
+- Issue #11459: A ``bufsize`` value of 0 in subprocess.Popen() really creates
+ unbuffered pipes, such that select() works properly on them.
+
 - Issue #5421: Fix misleading error message when one of socket.sendto()'s
 arguments has the wrong type. Patch by Nikita Vetoshkin.
 
-- 
Repository URL: http://hg.python.org/cpython
