Tim Williams <[EMAIL PROTECTED]> wrote:
> On 18/06/07, Nick Craig-Wood <[EMAIL PROTECTED]> wrote:
> On Windows the open-a-file-for-writing method works well, but as *nix
> doesn't work the same way then maybe the socket solution is the best
> cross-platform option.
Actually you could combine your solution and Jeff McNeil's solution to
make something which should work on both windows and unix and is 100%
guaranteed to release the lock on process exit.
import sys
try:
# use fcntl lock if we can
from fcntl import lockf, LOCK_EX, LOCK_NB
from errno import EAGAIN
locking = True
except ImportError:
# otherwise platform mustn't open a file twice for write
if sys.platform != "win32":
raise AssertionError("Unsupported platform for locking")
locking = False
try:
fhandle = file("ourlockfile.txt", "w")
if locking:
lockf(fhandle.fileno(), LOCK_EX|LOCK_NB)
except IOError, e:
if locking and e.errno != EAGAIN:
raise
print >>sys.stderr, "exiting, another copy currently running"
import time
time.sleep(2)
(I tested it on linux only!)
--
Nick Craig-Wood <[EMAIL PROTECTED]> -- http://www.craig-wood.com/nick
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