Re^5: [threads] Open a file in one thread and allow others to write to it

[BrowserUk]

you are assuming that OS will sync the File->writes without any race conditions problems,

Um. No. That's why I used a shared variable to coordinate

my $sem :shared;
open LOG, '>', 'log.txt' or die $!;


sub logit {
    lock $sem;
    return printf LOG @_;
}

Perhaps you could just try running the code I posted where you are, and tell me what problems you see?

[gulden]

«That's why I used a shared variable to coordinate »

Your lock variable coordinates the concurrency between Perl Threads, it won't sync the OS File->writes, cos each Thread is using a cloned FileHandled and you are trusting OS Synchronization.

Now I make you a question? Why are you using a lock variable, since you are using a cloned FileHandle that is not shared between threads? You are trusting the OS sync, so the use of that shared LOCK variable is useless.It only minimizes OS->File->Writes thread concurrency

[BrowserUk]

Why are you using a lock variable,

Because in the past I have (frequently) seen the situation where separate threads writing to the same file concurrently through buffered IO, would flush buffer-fulls, not lines, and so result in fragmentary interleaving.

And in the absence of anyone with demonstrably authoratative knowledge prepared to answer such questions, I go by the empirical eveidence of what actually happens when I do things.