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bpo-30404: The -u option now makes the stdout and stderr streams unbuffered. #1667

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Merged
serhiy-storchaka merged 5 commits into from
Oct 4, 2017
Merged

bpo-30404: The -u option now makes the stdout and stderr streams unbuffered. #1667

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1a465a5
bpo-30404: The -u option now makes the stdout and stderr streams unbu…
serhiy-storchaka May 19, 2017
014a0b0
Fix a typo.
serhiy-storchaka May 19, 2017
7cc95b2
Merge branch 'master' into unbuffered-stdout
serhiy-storchaka Jun 19, 2017
2b1f9c4
Move a NEWS entry to NEWS.d/.
serhiy-storchaka Oct 3, 2017
8c11707
Merge branch 'master' into unbuffered-stdout
serhiy-storchaka Oct 3, 2017
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8 changes: 4 additions & 4 deletions Doc/using/cmdline.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -303,13 +303,13 @@ Miscellaneous options

.. cmdoption:: -u

Force the binary layer of the stdout and stderr streams (which is
available as their ``buffer`` attribute) to be unbuffered. The text I/O
layer will still be line-buffered if writing to the console, or
block-buffered if redirected to a non-interactive file.
Force the stdout and stderr streams to be unbuffered.

See also :envvar:`PYTHONUNBUFFERED`.

.. versionchanged:: 3.7
The text layer of the stdout and stderr streams now is unbuffered.


.. cmdoption:: -v

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7 changes: 3 additions & 4 deletions Lib/test/test_cmd_line.py
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Expand Up @@ -221,13 +221,12 @@ def test_unbuffered_output(self):
rc, out, err = assert_python_ok('-u', '-c', code)
data = err if stream == 'stderr' else out
self.assertEqual(data, b'x', "binary %s not unbuffered" % stream)
# Text is line-buffered
code = ("import os, sys; sys.%s.write('x\\n'); os._exit(0)"
# Text is unbuffered
code = ("import os, sys; sys.%s.write('x'); os._exit(0)"
% stream)
rc, out, err = assert_python_ok('-u', '-c', code)
data = err if stream == 'stderr' else out
self.assertEqual(data.strip(), b'x',
"text %s not line-buffered" % stream)
self.assertEqual(data, b'x', "text %s not unbuffered" % stream)

def test_unbuffered_input(self):
# sys.stdin still works with '-u'
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2017-10-03-23-46-39.bpo-30404._9Yi5u.rst
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@@ -0,0 +1,2 @@
The -u option now makes the stdout and stderr streams unbuffered rather than
line-buffered.
12 changes: 8 additions & 4 deletions Python/pylifecycle.c
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Expand Up @@ -1498,7 +1498,7 @@ create_stdio(PyObject* io,
PyObject *buf = NULL, *stream = NULL, *text = NULL, *raw = NULL, *res;
const char* mode;
const char* newline;
PyObject *line_buffering;
PyObject *line_buffering, *write_through;
int buffering, isatty;
_Py_IDENTIFIER(open);
_Py_IDENTIFIER(isatty);
Expand Down Expand Up @@ -1555,7 +1555,11 @@ create_stdio(PyObject* io,
Py_DECREF(res);
if (isatty == -1)
goto error;
if (isatty || Py_UnbufferedStdioFlag)
if (Py_UnbufferedStdioFlag)
write_through = Py_True;
else
write_through = Py_False;
if (isatty && !Py_UnbufferedStdioFlag)
line_buffering = Py_True;
else
line_buffering = Py_False;
Expand All @@ -1574,9 +1578,9 @@ create_stdio(PyObject* io,
newline = "\n";
#endif

stream = _PyObject_CallMethodId(io, &PyId_TextIOWrapper, "OsssO",
stream = _PyObject_CallMethodId(io, &PyId_TextIOWrapper, "OsssOO",
buf, encoding, errors,
newline, line_buffering);
newline, line_buffering, write_through);
Py_CLEAR(buf);
if (stream == NULL)
goto error;
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