locking files on Linux

[Grant Edwards]

On 2012-10-18, andrea crotti <andrea.crotti.0 at gmail.com> wrote:
> 2012/10/18 Grant Edwards <invalid at invalid.invalid>:
>> On 2012-10-18, andrea crotti <andrea.crotti.0 at gmail.com> wrote:
>>
>> File locks under Unix have historically been "advisory".  That means
>> that programs have to _choose_ to pay attention to them.  Most
>> programs do not.
>>
>> Linux does support mandatory locking, but it's rarely used and must be
>> manually enabled at the filesystem level. It's probably worth noting
>> that in the Linux kernel docs, the document on mandatory file locking
>> begins with a section titled "Why you should avoid mandatory locking".
>
> Uhh I see thanks, I guess I'll use the good-old .lock file (even if
> it might have some problems too).
>
> Anyway I'm only afraid that my same application could modify the
> files, so maybe I can instruct it to check if the file is locked.

If what you're guarding against is multiple instances of your
application modifying the file, then either of the advisory file
locking schemes or the separate lock file should work fine.

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