File locking

[Michalis Kabrianis]

On 25-Aug-99 Bassoukos Tassos wrote:
> On Wed, 25 Aug 1999, Michalis Kabrianis wrote:
> 
>> 1) Thanks.
>> Ayta ta iksera (kai malista to oti afaireis ena arxeio alla ta inodes
>> paramenoun valid to antimetwpisa poly prosfata - molis xthes, kai exasa ligo
>> ton bousoula mexri na to katalabw), alla pali den yparxei tropos na min kanw
>> open ena idi locked arxeio. H na min kanw remove apo allo process, ena
>> arxeio
>> poy to prwto process den prolabe na anoiksei. Dystyxws diladi den mou lynoun
>> to
>> problima. Ektos an den katalaba kati.
> 
> Katarxhn, as arxisoume apo ta apla, giati me mperdepses ligo: xwris kernel
> modification den yparxei 'mandatory' locking, dhladh ena non-locking-aware
> programma mporei kallista na paei kai na grapsei panw se locked
> arxeia/perioxes arxeiwn, kai sy to mono pou mporeis na kaneis einai na
> alla3eis ta permissions tou arxeiou se -w[0] ... 

Good, ayto mou lynei tis perissoteres apories. 

> Ean twra milas gia programmata pou einai locking-aware[1], tote den
> yparxei problhma, giati aplws grafeis ena wrapper gyrw apo thn open() me
> onoma open_and_lock() pou kanei ayto akribws.

Kapws etsi tha to kanw telika. Tha xrisimopoiisw to trick pou xrisimopoioun
kapoia programmata, dimiourgwntas to "arxeio.lock" kai elegxontas tin yparksi
tou. Opws eipa kai ston Niko, efoson den mporw na epiballw sto systima kati,
toulaxiston tha to kratisw se epipedo efarmogis.

> Tassos
> [0] exw thn entypwsh pws ef'oson anoi3eis ena arxeio ws rw kai to kanei
>     -w, 8a synexiseis na mporeis na grafeis apo to syngekrimeno file
>     descriptor. Einai swsto ayto (kaneis ekei e3w? Ricudi?)
> [1] diabase: ta egrapses esy gia enan syngekrimeno skopo, px gia na
>     elengxeis apo pollous xrhstes thn idia bash etc.

Kati tetoio ([1]), tha exete plirofories molis proxwrisei ligo to project.

> -- 
> Bassoukos Tassos   +30 31 996011 / +30 93 7109954
>  Computer Shaman and Informatics Thaumaturge
> 
> The IQ of any group is the lowest individual
> IQ divided by the number of feet. - PCDC in /.
> 

Eyxaristw olous gia tin boitheia.

Michalis Kabrianis
kabrianis at hellug.gr
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