checking a file handle to see if it is open

powerhouse has asked for the wisdom of the Perl Monks concerning the following question:

Is there a way to test if a file handle like MAIL is open before I use close(MAIL)?

I have someone elses program I bought, and they have tons of stuff going on, then out of the blue they are running the command close(MAIL), and I am getting a recipient error, but the mail is getting sent out. So I think that close(MAIL) is called earlier, and when it is called again, since there is no MAIL open now, it is generating that error, so is there a way to do it like this or something: close(MAIL) if open(MAIL)?

or just close(MAIL) if MAIL;?

Thank you in advance for your wisdom.

thx,
Richard

Comment on checking a file handle to see if it is open

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Re: checking a file handle to see if it is open by Zaxo (Archbishop) on Apr 05, 2006 at 07:37 UTC
You can test if the handle is writable with -w HANDLE. That will return false if the handle has been closed. I suspect, though, that the errors are coming from the mail application instead of a double close. Here's what happens with a double close: `$ perl -w -e'open MAIL, ">", "/dev/null"; close MAIL or warn 1, $!; cl +ose MAIL or warn 2, $!' 2Bad file descriptor at -e line 1. $` [download] The second close would not pick up mail system errors, since the mail system is already dissociated from the dead handle. I think your problem is with the mail app, and you don't give much to go on for that. Lots of scripts people sell are not particularly well-written. Does yours use one of the standard CPAN Mail modules? After Compline, Zaxo	[reply] [d/l]
Re: checking a file handle to see if it is open by borisz (Canon) on Apr 05, 2006 at 07:31 UTC
`my $open = fileno($fh); # if open is NOT undef the file is open` [download] Boris	[reply] [d/l]
Re: checking a file handle to see if it is open by mickeyn (Priest) on Apr 05, 2006 at 07:29 UTC
Hi Richard, I guess what you asked for is something like: `close FH unless eof FH;` Enjoy, Mickey	[reply] [d/l]