fcntl.flock() doesn't work in solaris

[jcpm]

BPO	617870
Nosy	@loewis

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

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GitHub fields:

assignee = None
closed_at = <Date 2002-10-03.08:36:49.000>
created_at = <Date 2002-10-03.02:06:08.000>
labels = ['invalid', 'library']
title = "fcntl.flock() doesn't work in solaris"
updated_at = <Date 2002-10-03.08:36:49.000>
user = 'https://bugs.python.org/jcpm'

bugs.python.org fields:

activity = <Date 2002-10-03.08:36:49.000>
actor = 'loewis'
assignee = 'none'
closed = True
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2002-10-03.02:06:08.000>
creator = 'jcpm'
dependencies = []
files = []
hgrepos = []
issue_num = 617870
keywords = []
message_count = 2.0
messages = ['12565', '12566']
nosy_count = 2.0
nosy_names = ['loewis', 'jcpm']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue617870'
versions = []

[jcpm]

When trying the script below on Solaris:

# test_flock.py
import fcntl

def lock(fd, flags):
    fcntl.flock(fd.fileno(), flags)

def unlock(fd):
    fcntl.flock(fd.fileno(), fcntl.LOCK_UN)

fd = open('test.txt', 'w')
lock(fd, fcntl.LOCK_SH)
fd.write('testing')
unlock(fd)
fd.close()
# end of test_flock.py

$ uname -a
SunOS mercury 5.8 Generic_108529-13 i86pc i386 i86pc

I get the following output:

$ python test_flock.py
Traceback (most recent call last):
  File "test_flock.py", line 10, in ?
    lock(fd, fcntl.LOCK_SH)
  File "test_flock.py", line 4, in lock
    fcntl.flock(fd.fileno(), flags)
IOError: [Errno 9] Bad file number

This is the python version information:

$ python -V
Python 2.2.1

However, when I try the same script under Linux it works
correctly (i.e. it creates the 'test.txt' file)

$ uname -a
Linux domain.com 2.4.9-31 #1 Tue Feb 26 07:11:02 
EST 2002 i686 unknown

Please let me know if you need any more information.

[loewis]

Logged In: YES
user_id=21627

This is not a bug in Python, but a feature of your system.
From flock(3UCB):

 Read permission is required on a file  to  obtain  a 

shared
lock, and write permission is required to
obtain an
exclusive lock.

Since you haven't opened the file for reading, you can not
obtain a shared lock - you need an exclusive lock for writing.