Conference noted::hackers_v1

    This sounds like an exercise in coding, but relatively uninteresting.
    
    I believe you need to use SYS$OPEN, and friends to open the
    file, read the area you want to patch and write it back.   Am
    I missing something obvious?
    
    	KC

        To be specific, I want to replace one string with another
    of identical length.
        Can you send me an example?
    
    mike

P.S.  Talk about FAST replies!!

    
    As will using CONVERT
    
    /Bevin

    Are you trying to change some information in a record?  If so, this
    can be done from DCL using OPEN, READ, WRITE and CLOSE.  If you
    are trying to change something other than a data record, I would
    suggest PATCH/ABSOLUTE as recommended in a previous reply.

    tom_p

    I used PATCH/ABSOLUTE and the resultant file was sequential, even
    though the original was Prolog-3, indexed, etc.
    
    HELP says that the file attributes (?) are held over, but I guess
    the record type isn't one of them.
    
    What must I do to just change those bytes and keep all the other
    file attributes, etc intact?
    
    mike

        It looks like what I forgot was /NONEW_VERSION. This does
    the trick, now if I can find a way to non-manually search for
    the strings ...    any hints??
    
    mike

    What the hell do you want to ZAP? if it is a 'file attribute' then
    is should be in the prologue blocks and it would not require more
    then say 10 blocks dump to find it. If it is in the data then one
    wonders why a  normal rms update, available through youre favourite
    language (including DCL) can not do the job.
    If you do need a search from a program then the problem turns into
    a 'mere program exercise' as indicated previously. Actually I posted
    the frameworks of such a program a couple (20+) notes back.
    
    Regards,
    	Hein.

    [RE .9]:  ZAP is nice and cryptic.  Like TECO.
		<_Jym_>

    Complete!
    
    All is fixed, finally. I ended up with a DCL program that uses
    f$locate() to find the string, then substitutes the new one in
    its place. Only problem I encountered was a command buffer over-
    flow (maybe a record > 2048 bytes??), but that happened far
    enough into the file that it was OK.

    I didn't realize that something as simple as $read knew enough
    about Prolog-3 type files to handle them.
        
    mike

It's RMS that knows about prologue-3 (and other) indexed files.
When asked to retrieve records sequentially from an indexed file,
RMS simply does it.

BTW -- I have a little hack program for finding readable strings
in files.  This is useful (for example) to find the places in an
image that reference another image, or for checking that an image
does not contain embedded text.

    I wrote a program to do that back in my TOPS20 days.
    
    The program is quite useful !  For one thing, suppose you get an
    error saying
    
    		%F, No such logical name
    
    What logical name is program looking for ??  By running the
    asciizer, you may find the string containing the logical name.
    
    For another example,
    
    		% Unrecognized command
    
    What commands are legal?  Unfortunately I have no documentation.
    
    Well, the asciizer often prints out command lists, so it's useful
    here too.
    
    And of course the most useful :-) purpose of the asciizer is to
    print out all the messages from a cookie program.
    
    Peter, if you'd like to publish your program, it would be useful,
    thanks.
    
    /Eric

    While it lasts,...

    CLT::SYS$PUBLIC:C3.A is a backup asve-set containing the executable
    and a .CLD file (for reference only).  The image is invoked by a
    foreign command, but otherwise looks like the DCL command described
    in the .CLD file.