andy@cbmvax.UUCP (Andy Finkel) (11/01/88)
In article <9968@swan.ulowell.edu> page@swan.ulowell.edu (Bob Page) writes: >[followups to comp.sys.amiga.tech] > >andy@cbmvax.UUCP (Andy Finkel) wrote: >>Any file currently in use can't have its protection bits changes >>(under 1.1, 1.2, 1.3) Locks (ie Assigns) count as 'in use'. > >So why can't you look at "in use" file system resources? > >This has always seemed arbitrary to me, especially something as >harmless as poking attribute bits in the fileheader when another >process is reading the data in the file. I specified it as carefully as I did precisely because it may change in the future. We're not locked into having it work precisely the way it does now; on the other hand, we like to have a pretty good idea of the full implications of a change before we make it. > >But the real reason is I want to do the Unix equivalent of > >datagenerator >>logfile >tail -f file > >Sure, I can say > datagenerator | tee >>logfile >but that begs the question. I'm sure the answer can't be "because we >want to avoid race conditions" when you have something as notorious as >ExNext() out there. What a peculiar statement; possibly the running the source groups (BTW, you seem to be doing a great job so far) is effecting your mind. :-) Are you saying that because we have one area of vunerability, additional ones are OK ? Anyway, back to the request: You can do this now; there are dangers, certainly, but the worst that should happen is the file will get corrupted if you have 2 writers. It will be made safer in the future. (Using 1.3 AmigaShell you can do this on an existing file, ie echo >logfile datagenerator >>logfile tail -f logfile assuming, of course, that your tail doesn't want exclusive access. -- andy finkel {uunet|rutgers|amiga}!cbmvax!andy Commodore-Amiga, Inc. "I first began to lose faith in software engineering when I found out that no two printers were compatible." Any expressed opinions are mine; but feel free to share. I disclaim all responsibilities, all shapes, all sizes, all colors.
ditto@cbmvax.UUCP (Michael "Ford" Ditto) (11/01/88)
In article <5157@cbmvax.UUCP> andy@cbmvax.UUCP (Andy Finkel) writes: >In article <9968@swan.ulowell.edu> page@swan.ulowell.edu (Bob Page) writes: >>But the real reason is I want to do the Unix equivalent of >> >>datagenerator >>logfile >>tail -f file [ .. .] >> I'm sure the answer can't be "because we >>want to avoid race conditions" when you have something as notorious as >>ExNext() out there. >What a peculiar statement; possibly the running the source groups >(BTW, you seem to be doing a great job so far) is effecting your >mind. :-) Are you saying that because we have one area of vunerability, >additional ones are OK ? I think he meant that ExNext is such an intensely hairy thing to implement right, that proper support for file sharing is easy by comparison. I'll continue to be frustrated by AmigaDos's "file sharing" until it is the default mode for fopen(), shell redirection, etc., and all these "can't do FOO, object in use" errors no longer happen. -- -=] Ford [=- "The number of Unix installations (In Real Life: Mike Ditto) has grown to 10, with more expected." ford@kenobi.cts.com - The Unix Programmer's Manual, ...!sdcsvax!crash!elgar!ford 2nd Edition, June, 1972. ditto@cbmvax.commodore.com