in reply to Filehandle open?

The fcntl function allows you to read the filehandle's modes. If *FOO is open and you want to see if it is writeable: 

# named constants for portability
use Fcntl qw( F_GETFL O_WRONLY O_RDONLY O_RDWR);
if ( (O_WRONLY | O_RDWR) & fcntl( FOO, F_GETFL, 0) ) {
     # g'wan and write
}

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On many systems fcntl will return '0 but true' if the handle is open read only, so a writeable handle will return numeric zero or else have the O_RDWR bit set.

If the handle is not open fcntl returns undef.

Update: Aristotle, yes, but it would be good to check $! the see just what the error was. EBADF says the handle isn't open.

After Compline,
Zaxo

Replies are listed 'Best First'.
Re^2: Filehandle open?
by Aristotle (Chancellor) on Sep 24, 2002 at 14:37 UTC
    Wouldn't it then suffice to check like so? 
    sub is_opened {
    return defined fcntl $_[0], F_GETFL, 0;
}

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    Makeshifts last the longest.

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[d/l]

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