EAGAIN when sys.stdin.readline()

[frallan]

BPO	858253
Nosy	@gaul, @hyeshik, @tiran

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2008-01-20.19:02:40.971>
created_at = <Date 2003-12-11.13:12:22.000>
labels = ['extension-modules']
title = 'EAGAIN when sys.stdin.readline()'
updated_at = <Date 2008-01-20.19:02:40.969>
user = 'https://bugs.python.org/frallan'

bugs.python.org fields:

activity = <Date 2008-01-20.19:02:40.969>
actor = 'christian.heimes'
assignee = 'none'
closed = True
closed_date = <Date 2008-01-20.19:02:40.971>
closer = 'christian.heimes'
components = ['Extension Modules']
creation = <Date 2003-12-11.13:12:22.000>
creator = 'frallan'
dependencies = []
files = []
hgrepos = []
issue_num = 858253
keywords = []
message_count = 5.0
messages = ['60434', '60435', '60436', '60437', '61330']
nosy_count = 4.0
nosy_names = ['gaul', 'frallan', 'hyeshik.chang', 'christian.heimes']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue858253'
versions = ['Python 2.3']

[frallan]

$ cat test.py
import sys
print sys.stdin.readline()
$ python test.py | python test.py
Traceback (most recent call last):
  File "test.py", line 2, in ?
    print sys.stdin.readline()
IOError: [Errno 35] Resource temporarily unavailable

This happens about 3 times out of 5.
It happens under FreeBSD 5.1-RELEASE (SMP) and:
python-2.1.3
python-2.2.3
python-2.3.2
python-2.3.3c1

It does _not_ happen under Debian 3.0 or
FreeBSD 4.7-RELEASE (SMP).

According to read(2) this "error" should occur only when
the descriptor is in non-blocking mode. However as you
can see from the program it isn't. Further I have caught
the IOError and run fcntl(F_GETFL) on sys.stdin.fileno()
and the only flag set is O_RDWR.

[gaul]

Logged In: YES
user_id=139865

Same on OpenBSD:

$ uname -a
OpenBSD owl 3.2 GENERIC#25 i386
$ python -V
Python 2.2.1
$ python test.py | python test.py
Traceback (most recent call last):
  File "test.py", line 2, in ?
    print sys.stdin.readline()
IOError: [Errno 35] Resource temporarily unavailable

[hyeshik]

Logged In: YES
user_id=55188

I could not reproduce the error on several versions of FreeBSD:

5.2-BETA Thu Dec 4 21:59:16 KST 2003 i386 (non-SMP)
5.2-CURRENT Sat Dec 13 08:02:47 PST 2003 alpha (SMP)
5.2-CURRENT Tue Dec 9 02:39:36 PST 2003 ia64 (SMP)
5.2-CURRENT Sat Dec 13 07:52:29 PST 2003 i386 (SMP)
5.1-RELEASE Sat Jun 14 05:13:38 KST 2003 i386 (SMP)

Do you have any uncommon factor of environment?
(and did you install the python via ports?)

[frallan]

Logged In: YES
user_id=639616

All my python versions are compiled from source.

Further, since the problem only occur some of the time and
only on some of the platforms, it's natural to suspect foul play
from the runtime environment (i.e shell, OS) and that it might
not be a bug in python. It's not like blocking input should be a
black art.

I refuse to believe that this issue has never been raised
before and subsequently solved. It's just a matter of finding
the right mailing list archive. The alternative seems to be
hacking the interpreter and try to narrow it down.

[tiran]

The bug is probably outdated. Please create a new issue if the bug still
occurs for you with newer versions of Python and your OS.