[NTLUG:Discuss] File Locking

[Chris Cox]

Patrick R. Michaud wrote:
> On Thu, Apr 12, 2007 at 11:12:26PM -0500, Chris Cox wrote:
>> Dennis Rice wrote:
>>> A co-worker would like to set up a file as being locked when a user 
>>> opens it, so that others can not write to the file.  I am not aware of 
>>> any permission / attribute that can do this.  Anyone have an idea or 
>>> suggestion?  Appreciate.
>> Though I don't recommend it... you can open a file with an exclusive
>> lock on it (an OS wide lock).  However, if you forget to unlock, it
>> will cause things like your backups to hang since the file is forever
>> locked.
>>
>> man flock
>>
>> (you may only have the function call... openSUSE has flock(1))
> 
> To add a bit more information... flock provides "advisory" locking
> (as opposed to "mandatory" locks).  Advisory locking blocks
> only those processes that attempt to set a lock with flock --
> processes that aren't using flock can still open and write to
> files that are "locked" with flock.
> 
> Mandatory locks are performed using the fcntl(2) and/or lockf(3)
> function calls, and yes, if a process uses mandatory locking on
> a file it can cause problems for other programs that may try
> to access that file.

Uh... yes... that's what I meant (my oops).

I was just so happy to see a command line flock!!