FAQ 5.35 How do I close a file descriptor by number?

Discussion in 'Perl Misc' started by PerlFAQ Server, Mar 17, 2011.

  1. This is an excerpt from the latest version perlfaq5.pod, which
    comes with the standard Perl distribution. These postings aim to
    reduce the number of repeated questions as well as allow the community
    to review and update the answers. The latest version of the complete
    perlfaq is at http://faq.perl.org .

    --------------------------------------------------------------------

    5.35: How do I close a file descriptor by number?

    If, for some reason, you have a file descriptor instead of a filehandle
    (perhaps you used "POSIX::eek:pen"), you can use the "close()" function
    from the "POSIX" module:

    use POSIX ();

    POSIX::close( $fd );

    This should rarely be necessary, as the Perl "close()" function is to be
    used for things that Perl opened itself, even if it was a dup of a
    numeric descriptor as with "MHCONTEXT" above. But if you really have to,
    you may be able to do this:

    require 'sys/syscall.ph';
    my $rc = syscall(&SYS_close, $fd + 0); # must force numeric
    die "can't sysclose $fd: $!" unless $rc == -1;

    Or, just use the fdopen(3S) feature of "open()":

    {
    open my( $fh ), "<&=$fd" or die "Cannot reopen fd=$fd: $!";
    close $fh;
    }



    --------------------------------------------------------------------

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    are not necessarily experts in every domain where Perl might show up,
    so please include as much information as possible and relevant in any
    corrections. The perlfaq-workers also don't have access to every
    operating system or platform, so please include relevant details for
    corrections to examples that do not work on particular platforms.
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    PerlFAQ Server, Mar 17, 2011
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