[tex-live] ctan->tl updates caught up

[Zdenek Wagner]

2012/8/3 Philip TAYLOR <P.Taylor at rhul.ac.uk>:
>
>
> Zdenek Wagner wrote:
>
>> I cannot answer. I switched from DOS+Windows 3.0 to OS/2 in 1994, thus
>> I do not know the Windows specific details. Maybe I have old notes how
>> it worked on DOS but most probably, if I still keep them, they may be
>> on an old 5 1/4" diskette for which I do not have a drive any longer.
>
>
> OK, but it was not a Windows question (particularly as we already
> know from Tomek that that step may be omitted on Windows without
> any obvious harm).  It is a more general question, applicable to
> any operating system.  Q1 :  When TAR creates a file, does it set
> "last modified" to "time created", as it has not yet been modified.

In Linux it cannot, last-modified is set by the file system driver
whenever the file is modified and a program cannot change it.

> And Q2 :  If so, why is it then necessary to adjust "last modified"
> as a separate step ?
>
If tar writes the file (at least in Linux), last modified and created
are set automatically to the same value, ie to the time when it was
written (more precisely to the time when the file was closed). In the
next step the time created is set to the time when the original file
was created (that time is written in the tar archive). When the time
created is changed, the last modified time is also changed
automatically. The difference may not be easy to understand. In fact
when developing an automatic system requiring network safe atomic
locks and semaphores with recovery after power and network failures it
took me some time to find out why the programs do not work and how to
do it properly.

> ** Phil.



-- 
Zdeněk Wagner
http://hroch486.icpf.cas.cz/wagner/
http://icebearsoft.euweb.cz