in reply to Re: Re: File::Grep
in thread File::Grep


I ran into this problem in the past when trying to allow a function to accept filenames or filehandles.

From my testing at the time I don't think it is possible to determine if a scalar is a filehandle or not. As you point out the IO:: objects would be difficult to handle.

The solution that I can up with was just to assume that any references passed to the function were filehandles and any scalars were filenames. Here is an extract from the code. 

    # If the filename is a reference it is assumed that it is a valid
    # filehandle, if not we create a filehandle.
    #
    if (ref($OLEfile)) {
        $fh = $OLEfile;
    }
    else {
        # Create a new file, open for writing
        $fh = FileHandle->new("> $OLEfile");
        if (not defined $fh) {
            croak "Can't open $OLEfile. ......";
        }

        # binmode file whether platform requires it or not
        binmode($fh);

    }

    # Store the filehandle
    $self->{_filehandle} = $fh;

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This isn't bullet-proof but if the documentation is explicit then it may be sufficient.

--
John.

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Re: Re: Re: Re: File::Grep
by Masem (Monsignor) on Jan 22, 2002 at 20:20 UTC
    Yea, I think that will be a better solution. The only point, after I've opened the file, that I actually care if it's a file is the overall while loop, so as long as I start that loop with an open filehandle or an IO::File object, I can just do the while loop on it: 
    while ( my $line = <$current_file> ) { ... }
# $current_file can be a filehandle or an IO::File obejct
# or anything else that responds appropriately in the < >
# construct.

    [download]
    Besides making that change, I think I'll also closure-off the internals of that loop; it will be much easier to write the other suggested functions that I put in the desc of this code; in addition, I can see an 'fmap' function and a few other things that as long as I have a function that determines what you do with a line, it doesn't matter what else goes on.

    -----------------------------------------------------
    Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
    "I can see my house from here!"
    It's not what you know, but knowing how to find it if you don't know that's important

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