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Re^3: Can't close pipe to invalid process

by BrowserUk (Patriarch)
on Aug 28, 2015 at 22:50 UTC ( [id://1140387]=note: print w/replies, xml ) Need Help??

in reply to Re^2: Can't close pipe to invalid process
in thread Can't close pipe to invalid process

I guess my concern is why the invalid open returned true.

Because the (piped) open succeeded. It found and successfully ran the prince executable.

The problem is that you are attributing the failed close to the failure to find the non-existent file; which is wrong.

What you are attempting to close is the pipe to the prince executable; which fails because the executable closed its end of the pipe, when it terminated because it couldn't find the file.

Bottom line: You cannot close the pipe because it is already closed. The confusion arises because you are attributing the failed close to the failure of the file to exist; rather than the fact the the pipe was already closed.

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Re^4: Can't close pipe to invalid process
by ikegami (Patriarch) on Aug 31, 2015 at 18:00 UTC

    That's completely wrong.

    1. Closing one end of a pipe doesn't cause close on the other end to return an error.

    $ perl -E' pipe($r, $w) or die $!; close($w) or die $!; close($r) or die $!; say "ok"; ' ok

    2. Closing a pipe created by open(my $fh, '|-', ...) reads the process (calls wait). It's very appropriate to do this, whether the pipe is closed or not. Closing such a handle returns the same thing as system.

    $ perl -E' open(my $fh, "|-", "perl", "-e", "exit 123") or die $!; close($fh); die("$!\n") if $? == -1; die("Signal ".( $? & 0x7F )."\n") if $? & 0x7F; die("Error ".( $? >> 8 )."\n") if $? >> 8; say "ok"; ' Error 123

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