From: Antoine Pitrou <solipsis@pitrou.net>
Date: Sat, 19 Mar 2011 16:06:22 +0000 (+0100)
Subject: Issue #11459: A `bufsize` value of 0 in subprocess.Popen() really creates
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1679f4daa1b324bba87d952bc7da2c3e37f315fd;p=python

Issue #11459: A `bufsize` value of 0 in subprocess.Popen() really creates
unbuffered pipes, such that select() works properly on them.
---

1679f4daa1b324bba87d952bc7da2c3e37f315fd
diff --cc Lib/platform.py
index fb65b4ba34,abe917a4d5..75bc5f3b97
--- a/Lib/platform.py
+++ b/Lib/platform.py
@@@ -357,7 -357,61 +357,7 @@@ def dist(distname='',version='',id=''
                                supported_dists=supported_dists,
                                full_distribution_name=0)
  
- def popen(cmd, mode='r', bufsize=None):
 -class _popen:
 -
 -    """ Fairly portable (alternative) popen implementation.
 -
 -        This is mostly needed in case os.popen() is not available, or
 -        doesn't work as advertised, e.g. in Win9X GUI programs like
 -        PythonWin or IDLE.
 -
 -        Writing to the pipe is currently not supported.
 -
 -    """
 -    tmpfile = ''
 -    pipe = None
 -    bufsize = None
 -    mode = 'r'
 -
 -    def __init__(self,cmd,mode='r',bufsize=None):
 -
 -        if mode != 'r':
 -            raise ValueError('popen()-emulation only supports read mode')
 -        import tempfile
 -        self.tmpfile = tmpfile = tempfile.mktemp()
 -        os.system(cmd + ' > %s' % tmpfile)
 -        self.pipe = open(tmpfile,'rb')
 -        self.bufsize = bufsize
 -        self.mode = mode
 -
 -    def read(self):
 -
 -        return self.pipe.read()
 -
 -    def readlines(self):
 -
 -        if self.bufsize is not None:
 -            return self.pipe.readlines()
 -
 -    def close(self,
 -
 -              remove=os.unlink,error=os.error):
 -
 -        if self.pipe:
 -            rc = self.pipe.close()
 -        else:
 -            rc = 255
 -        if self.tmpfile:
 -            try:
 -                remove(self.tmpfile)
 -            except error:
 -                pass
 -        return rc
 -
 -    # Alias
 -    __del__ = close
 -
+ def popen(cmd, mode='r', bufsize=-1):
  
      """ Portable popen() interface.
      """
diff --cc Lib/test/test_subprocess.py
index 2dde245817,01e670ef72..6523c8a97e
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@@ -1313,8 -1214,24 +1313,24 @@@ class POSIXProcessTestCase(BaseTestCase
          stdout, stderr = p.communicate()
          self.assertEqual(0, p.returncode, "sigchild_ignore.py exited"
                           " non-zero with this error:\n%s" %
 -                         stderr.decode('utf8'))
 +                         stderr.decode('utf-8'))
  
+     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()
+ 
  
  @unittest.skipUnless(mswindows, "Windows specific tests")
  class Win32ProcessTestCase(BaseTestCase):