New submission from STINNER Victor <[email protected]>:
I like and I need an "unbuffered" standard output which was provided
by -u command line option (or PYTHONUNBUFFERED environment variable).
Current status of -u option in Python3: the option exists and change
the buffer size (disable buffering) of the stdin, stdout and stderr
file descriptors.
The problem is in initstdio() which creates files with buffering=-1
(default buffer) instead of buffering=0 (no buffering) or buffering=1
(line buffer). But open() enable line buffering of TextIOWrapper is
buffering=-1 and the raw file is a tty.
Example with py3k trunk:
------------
$ ./python
>>> import sys; sys.stdout.line_buffering
True
$ ./python |cat
>>> import sys; sys.stdout.line_buffering
False
------------
I would like line buffering when stdout is redirected to a pipe and -u
option is used. initstdio() have to be changed to choose buffering
option. So it's something like:
Index: Python/pythonrun.c
===================================================================
--- Python/pythonrun.c (révision 67870)
+++ Python/pythonrun.c (copie de travail)
@@ -810,7 +810,12 @@
#endif
}
else {
- if (!(std = PyFile_FromFd(fd, "<stdout>", "w", -1,
encoding,
+ int buffering;
+ if (1)
+ buffering = 1; /* line */
+ else
+ buffering = -1; /* default */
+ if (!(std = PyFile_FromFd(fd, "<stdout>", "w",
buffering, encoding,
errors, "\n", 0))) {
goto error;
}
But "if (1)" have to be replaced "if -u option is used" :-) See
unbuffered variable of Modules/main.c.
----------
messages: 78102
nosy: haypo
severity: normal
status: open
title: python3.0 -u: unbuffered stdout
versions: Python 3.0
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Python tracker <[email protected]>
<http://bugs.python.org/issue4705>
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