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in reply to Distinguishing a filehandle for an in-memory string

What you want to know is whether it's a system file handle or not. You can use fileno for that. It returns -1 for file handles that aren't system file handles (such as the in-memory string handles).

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Re^2: Distinguishing a filehandle for an in-memory string
by jrw (Monk) on May 18, 2018 at 11:36 UTC
    I noticed this, but I saw somewhere in a comment or in some piece of documentation that it says something like "currently returns -1", which made me think that that is not a reliable way to check. But maybe it's as reliable as checking for "scalar" in the list of IO layers?

      Checking for an in-memory handle is not what you want to check for. It's only one kind of Perl file handle that's not a system file handle.