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On Tue, 31 Dec 2002 15:31:47 -0500, "Kipp, James" <[EMAIL PROTECTED]> wrote:
>
>
> > I am making a call to gpg on the command line, a couple of
> > the parameters that gpg will accept are file descriptor
> > numbers that it then writes to, and I would like to capture
> > that output and then read from it.
> >
> > I have successfully made it read directly from a file on the
> > local file system like so:
> >
> > my $pass_fh = IO::File->new('/path/to/localfile');
> > fcntl $pass_fh, F_SETFD, 0; # don't close over exec
> > my $pass_fd = $pass_fh->fileno(); # get the file descriptor number
> >
> > and then calling gpg on the command line like so:
> >
> > gpg [other options here, etc.] --passphrase-fd $pass_fd [etc.]
> >
> > Which works very well. And I can successfully create a new
> > file handle,
> >
> > my $logger_fh = IO::Handle->new();
> >
> > And then presumably could use the same methods as above, but
> > the file handle has to be open to determine its number and
> > then to pass the file descriptor to the command line. Which I
> > determined is what fdopen is for, so now to my question(s)
> > (finally, sorry about that) how do I determine what the FD
> > (file descriptor number) should be that I pass to fdopen? Is
> > this an arbitrary number (not 0,1,2), can I have the system
> > suggest a number? If the program were to choose the same
> > number in different forks would it matter? Is there a better
> > more appropriate way of handling all of this? (Besides using
> > one of the GPG modules from CPAN, which I would absolutely
> > love, but after spending a number of days checking them out,
> > each one has one or more quirks which doesn't allow it to
> > work in our app.)
>
> I am not sure if this helps or if you already knew this, but the camel book
> has section on it in chapter 16, under the 'Passing File' Handles section.
I had seen that and been through it a couple times, for another issue, but went
through it again, can't hurt right ;-), but all of the examples seem to open an
already existing file, creating a file, or using a handle as part of a pipe. It did
give me the idea of trying to open a new file handle with the "-|" syntax to open but
that just errored, and left $! blank which is odd to me...
> also the fdopen manpages states that you obtain an existing FD from open,
> fcntl.....
Right, but I am not sure how to get an existing FD without attaching it to an actual
normal file through an open call. the fdopen essentially attaches a separate handle
to the existing file descriptor, but I need to know how to generate a file descriptor
without attaching it to a file on the filesytem, if this can be done at all, at least
at Perl's high level, as this is seemingly done by 'pipe'.
> So i assume the open method in IO::File is really the open2
> system call.
I believe IO::File is just a sub class of IO::Handle, and fdopen just wraps a regular
open call.
> Also are you loading the Fcntl module in the program so you get all of the
> constants from cntl.h?
Yes, that is how I am setting the filehandle to stay open through the exec (system in
my case). But I am not familar with what that gets me as I don't make much of a C
programmer (yet hopefully ;-)), any suggestions on what I can use from it for this
problem?
> Don't know if this helps you at all, but thought i would give throw it out
> there.
>
Thanks, discussion can't ever hurt thats for sure.
>
> ps.. I can send you the HTML section on this if you don't have it handy.
>
Got it. Don't leave home without it.
thanks again for any help,
http://danconia.org
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