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    SubjectRe: sed not working on /proc files
    On Mon, Apr 26, 1999 at 09:15:56PM -0400, Richard B. Johnson wrote:
    > On Mon, 26 Apr 1999, Chip Salzenberg wrote:
    > > According to Jeremy Fitzhardinge:
    > > > On 26-Apr-99 Stefan Monnier wrote:
    > > > > open("/proc/meminfo", O_RDONLY) = 3
    > > > > fstat(3, {st_mode=0, st_size=0, ...}) = 0
    > > > > mmap(0, 0, PROT_READ, MAP_PRIVATE, 3, 0) = 0
    > > > This is the problem. It stats the file, mmaps 0 bytes from it and finishes
    > > > with no action. Presumeably if the mmap failed or stat said the file isn't a
    > > > regular file it would use normal read.
    > > Hm. Would it be a Bad Thing for mmap to fail on /proc files that
    > > don't report true sizes?
    > I don't know. And I don't know how to make it fail. I understand that
    > the reason why most sizes are not reported are that sizes are dynamic,
    > i.e., /proc/interrupts is bigger each time a value increase over 10. Since
    > the /proc file-system does know when a directory access is made, it
    > might be a good idea to actually calculate the length (but only at
    > directory access time, not when data are being accumumated which would
    > be a large overhead that is wasted because /proc is seldom read.

    > It is also possible to just return a size of, maybe, 1024 bytes for
    > each of the files that are normally 0 size. I don't think a premature
    > EOF would affect most Unix tools. This would have zero overhead and
    > might make life easier.

    /proc files could pretend to be pipes. Would it spoil any programme behaviour?

    R.

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