Using "send...in <time>" wirh private commands?

[Bob Sneidar]

One thing you might want to do using this process is to wait a period of time before trying to read or write to said file. Unix based operating systems will create a placeholder file prior to writing the actual file so that another process cannot use that filename in the middle of a write operation. I suppose you can also try to open the file for write even if you only want to read, which the OS will not allow while it is writing to it.

Bob S


On Nov 7, 2015, at 10:58 , Richard Gaskin <ambassador at fourthworld.com<mailto:ambassador at fourthworld.com>> wrote:

PS - a pleasant timing surprise:

One of the things I was testing this morning was the CPU impact of frequently polling for the existence of a file.  I have two processes which (for reasons not worth getting into here) can't talk via sockets, so I wondered how inefficient it might be to have them communicate via files.  Turns out checking for the existence of a specified file isn't bad at all.

Testing a worst-case I polled every millisecond and it never chewed up more than 4% of CPU time.  Throttling back to a more reasonable 500 ms never registered higher than 0%.

Not sure how well that would work on Windows, but OS X and Linux file system caching seems to make even brute force solutions like polling pretty nice.

--
Richard Gaskin