How Do You Do File Locking in Raku?

Question

I've been trying to figure out how to do file locking in Raku without success. I started looking into fcntl with NativeCall, but then realized that fcntl locks don't prevent file access from other threads. What's the best way to do file locking in Raku?

Maybe IO lock method is what you are looking for: [lock](https://docs.raku.org/type/IO::Handle#method_lock) — LuVa, Dec 28 '20 at 20:40
That's embarrassing. I looked all over and didn't see that. Thanks @ValleLukas! — JustThisGuy, Dec 28 '20 at 21:06

score 12 · Accepted Answer · answered Dec 28 '20 at 21:30

12

IO::Handle has a lock and an unlock method to lock/unlock files. Locks can be exclusive or shared.

answered Dec 28 '20 at 21:30

LuVa

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2
10
20

score 1 · Answer 2 · answered Jan 11 '21 at 20:17

1

I've come across these Raku-idiomatic phrases and use them a lot, with 'given' topicalizing for brevity/clarity:

Read:

    given $path.IO.open {
        .lock: :shared;
        %data = from-json(.slurp);
        .close;
    }

Write:

    given $path.IO.open(:w) {
        .lock;
        .spurt: to-json(%data);
        .close;
    }

answered Jan 11 '21 at 20:17

markldevine

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This doesn't unlock if the middle line throws an exception, a LEAVE phases may be helpful to ensure that – Leon Timmermans Jan 12 '21 at 01:55

How Do You Do File Locking in Raku?

2 Answers2