[fpc-pascal] Configuration file handling

Marco van de Voort marcov at stack.nl
Sat Feb 16 11:05:07 CET 2013

In our previous episode, Mark Morgan Lloyd said:
> If multiple, related, programs running on unix (Linux, Solaris etc.) 
> refer to the same configuration file accessed via a TIniFile, is there 
> any recommended "good practice" to ensure that they don't try to update 
> it simultaneously?
> In the case that I'm thinking of, I don't anticipate e.g. multiple 
> logins trying to write setup information at the same time

That sounds like the domain of of filelocking (fp)Flock.

> The more risky case is if there are e.g.  multiple daemons or apps trying
> to save state when a UPS signals imminent shutdown.

Have all systems regularly write local files in something that is not
cleared on startup.  (e.g.  change clearing /tmp to a monthly cronjob
instead of startup) 

On startup check for crash (local file exists) and if the
local file is newer than the server, copy and continue starting up.

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