file locking and file()

Anon

Though I'm not sure how much it is needed in my situation I like to use file locking to ensure the integrity of my datafiles. Normally I do this:

$fp = fopen($filename, "r");
flock($fp, LOCK_SH);

but since my datafiles are all \n delimited I've started using the file() function because of its convienence in reading full lines.

Is there any way to use file locking with file()?

darn, I wish my ISP had a database.

-j

Anon

I'd suggest ignoring locking and instead append to the files when you need to write to the file. If you can arrange your data structures to do this, it'd be good.

flock() is advisory ONLY - meaning that there's really no guarantees at all.

If you can't append, try writing to temp files, then have a background process update the main data file every 30 minutes or so. This way, there's only 1 process doing writes.

Why are you locking on a read? Reads don't change file content.

-Ben

PS: I host sites with database access...

Anon

I'm trying to lock on a read because I need to update the data and I don't want anyone writing to the file inbetween.

I wish I could append. I'm using flock() mostly as an extra percaution. I should have issues with the site as traffic will be very low. But even an advisory lock helps reduce the slight chance to slim.

If I had access to the cron I'd follow your suggestions, but alas.

-j

re PS: if your database hosts happen to be free, no-ad, no-pop-up, no-pop-under, well then drop me a line and I'll move over immediately. Otherwise I guess I need to choose my vice.

Anon

Is this on a unix system?

If so, you needn't worry about the file being updated while you read it - Unix/Linux doesn't work like that.

Once you start reading a file (under *nix) it doesn't change for the process reading it, even if another user changes it in the background.

It's almost like there are TWO copies of the file - one that's being read, and another being written to.

So this is simply not a worry. On a Windows system, well, I can't say. =(

Good luck!

-Ben

PS: No, not free, but I can do everything else. Alas, I begin hosting at $20/month, or about 65 cents per day 😉