write to the same file from multiple processes at the same time?

[gabor]

gabor wrote:
> Jp Calderone wrote:
> 
>> To briefly re-summarize, when you want to acquire a lock, attempt to 
>> create a directory with a well-known name.  When you are done with it, 
>> delete the directory.  This works across all platforms and filesystems 
>> likely to be encountered by a Python program.
> 
> 
> thanks...
> 
> but the problem now is that the cgi will have to wait for that directory 
>  to be gone, when he is invoked.. and i do not want to code that :)
> i'm too lazy..
> 
> so basically i want the code to TRY to write to the file, and WAIT if it 
>  is opened for write right now...
> 
> something like a mutex-synchronized block of the code...
> 
ok, i ended up with the following code:

def syncLog(filename,text):
     f = os.open(filename,os.O_WRONLY | os.O_APPEND)
     fcntl.flock(f,fcntl.LOCK_EX)
     os.write(f,text)
     #FIXME: what about releasing the lock?
     os.close(f)

it seems to do what i need ( the flock() call waits until he can get 
access).. i just don't know if i have to unlock() the file before i 
close it..


gabor