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Re: too many file handles

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Elizabeth Mattijsen
March 17, 2021 17:55
Re: too many file handles
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> On 17 Mar 2021, at 18:45, Richard Hainsworth <> wrote:
> I have been running into this error: "Too many open files"
> Sorry for the lack of detail. The problem is that the error comes up in odd places, so I have found it difficult to golf down into Raku program that always fails with this error.
> When I separate out the code that leads to the error, and create another program, Raku handles it without difficulty. It seems to occur when there are a lot of moving parts, so to speak.
> I am not explicitly opening file handles, but the software I have written is using the idiom
> "some-filename.html".IO.spurt( $an-accumulated-string );
> Obviously, filehandles are being opened under the hood. Having written a file, there is no need to reference it again, so I could close the filehandle.
> I have been told that because of the way garbage handling is implemented, there is a problem with file handles.

That's should only happen if you specifically open a file to obtain an IO::Handle: if you don't close it yourself (e.g. via a LEAVE block like: LEAVE .close with $handle), *then* you run this risk, as the IO::Handle.DESTROY method *will* close the handle, but you cannot be sure as to when IO::Handle.DESTROY gets called.

> If so, what is a safer idiom to use in place of and IO on a string, so that the handle can be closed immediately after use?

The "filelame".IO.spurt($string)" is the exact idiom to ensure that file handles are getting closed for you automatically.  And I've just checked the code: the OS file handle *is* specifically getting closed with an nqp::closefh($!PIO).  Specifically, the sequence is:

    my $PIO := nqp::open($path,$mode);

Now, you can't get more succinct than that: it doesn't even open an IO::Handle at all!

The only thing I can think of at this moment, is that somehow nqp::closefh() is leaking?  Perhaps creating an issue for this, is in order!


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