Re: [xslt] read XML File - atomic action?

[Daniel Veillard <veillard redhat com>]

On Fri, Sep 07, 2001 at 08:12:19PM +0200, Bernhard Zwischenbrugger wrote:
> Hi
> 
> In my software there are prozesses that write an XML-File an
> prozesses that read this XML-File.
> (apache, php)
> 
> My question:
> Are the read and write operations of xsltproc
> atomic operations?

 no they are progressive.

> Is it a problem if the xml-file is modified while
> xsltproc reads this files?

  I can be a problem if there isn't some underlying synchronization
done at the filesystem level.
  For example on a POSIX system if you do the following
    Process 1                  Process 2
    open( ,"r")
    read()                     open(, "w")
    read()                     write()
    read()                     write()
    close()                    write()
                               close()

  you may end-up with incoherent data. However

    Process 1                  Process 2
    open( ,"r")                unlink()
    read()                     open(, "w")
    read()                     write()
    read()                     write()
    close()                    write()
                               close()

is safer, in the sense you may get a retryable error on open("r") but won't get
corrupted data.

Daniel

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