[OpenIndiana-discuss] shell script mutex locking or process signaling

[Hugh McIntyre]

Gary already pointed to SMF contracts, but one other option if you want 
to use pure locking is to use the "lockfile" program that comes with 
procmail, for email.  Even though this may be a bit heavy handed for 
performance.

If you know you have a limited use case (all processes on the same host, 
non-NFS filesystem, only Illumos) then the problem becomes simpler, but 
if not then the people who've worked out how to lock mailbox files have 
worked out all of the ugly corner cases on different systems.

Hugh.


On 5/30/13 11:17 AM, Tim Mooney wrote:
> In regard to: Re: [OpenIndiana-discuss] shell script mutex locking or...:
>
>> On 30/05/13 16:15, Edward Ned Harvey (openindiana) wrote:
>> <snip>
>>> I see there are a bunch of C constructs available ... mutex_init,
>>> etc.  Surely there must be a wrapper application around this kind of
>>> thing, right?
>>
>> I spent some time looking for a lock in shell some time ago. The
>> overall conclusion was that the only atomic operation in pure shell is
>> mkdir.
>>
>> I use /tmp or /var/run so it's at least deleted on reboot, and my
>> scripts trap signals so when it ends (either correctly or after being
>> interrupted),
>
> In my experience, mkdir is also the easiest reliable mechanism.
>
> It's perhaps unfortunate that there's an ipcs and an ipcrm, but no
> ipcmk.  That would be the logical way to do what the original poster
> is asking about.
>
> Tim