Re: launching another program but using the existing socket

When you exec another process it has access to any open file-handles within your program whose system file desriptor is within the value of $^F.

The system uses file numbers 0=STDIN, 1=STDOUT, 2=STDERR and anything else is higher.

To open using just the fileno, first discover the socket's using fileno($socket) or $socket->fileno and pass that to the execed program on command line or with environment variables.

Then use the open syntax open FOO, ">& $fileno"; or whatever it is in the open documentation, or use $fh = File::Handle->new_from_fd and $fh->fdopen with the fileno.

Alternativly follow nardo's advice because those filehandles are always inherited by an exec'ed process and that will make the client program compatible with inetd.

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(tye)Re: launching another program but using the existing socket by tye (Sage) on Jul 23, 2001 at 23:57 UTC
A couple of fairly minor points: First, you probably want `open FOO, ">&=$fileno"` as using `">&$fileno"` will dup() the file descriptor and then open a Perl file handle to it, leaving you with two file descriptors open to the same socket so that closing just the one doesn't shut down the connection. Second, I recall recently someone discovering that sockets in Perl are never set to "close on exec" no matter what you do with $^F. I supposed you could consider this a feature, especially in this case. But I'd be a bit shy of depending on it until I found out why it is that way. - tye (but my friends call me "Tye")	[reply] [d/l] [select]

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(tye)Re: launching another program but using the existing socket
by tye (Sage) on Jul 23, 2001 at 23:57 UTC

A couple of fairly minor points:

First, you probably want open FOO, ">&=$fileno" as using ">&$fileno" will dup() the file descriptor and then open a Perl file handle to it, leaving you with two file descriptors open to the same socket so that closing just the one doesn't shut down the connection.

Second, I recall recently someone discovering that sockets in Perl are never set to "close on exec" no matter what you do with $^F. I supposed you could consider this a feature, especially in this case. But I'd be a bit shy of depending on it until I found out why it is that way.

tye

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