Start application & continue after app exits

Terry Reedy tjreedy at udel.edu
Fri Jun 10 19:23:06 CEST 2005


"Guy Lateur" <guy.lateur at b-b.be> wrote in message 
news:GXcqe.115625$Cx4.6765668 at phobos.telenet-ops.be...
> To be honest, I don't really understand what it means to have the same 
> file open for writing by several processes. You don't want to modify data 
> which is already being modified by someone else, do you? I mean, how do 
> you determine what changes to apply first, and to what version? Or is the 
> file just constantly being overwritten on a first-come-first-served 
> basis?

You have identified the reasons an operating system may not allow more than 
one process to open a file for writing.  These are also a major issue with 
multiuser database systems and multiprogrammer source-code control systems. 
The overwrite problem exists even with unique access, since one 
open-write-close can be followed by another open-write-close containing 
edits based on reading the file before the intervening write, so that the 
update is to a now obsolete version.  Various solutions include locks, 
checkouts, and conflict notifications.

Terry J. Reedy






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