topic Re: COM file to do DIFF in Operating System - OpenVMS

COM file to do DIFF

Jdavid — Mon, 05 Feb 2007 09:22:09 GMT

Hey all,

I'm new to DCL and OpenVMS and am trying to create a COM file that could do a DIFF between 2 versions of a file, for all the files in a directory.

Is this possible?, or is there any code/script out there that does this already?

Thanks

Re: COM file to do DIFF

Jan van den Ende — Mon, 05 Feb 2007 09:53:16 GMT

Jdavid,

to begin with:

Welcome to OpenVMS, and to the Forum!

$ HELP LEX is your friend here.

Try something along this line:

$loop:
$ next = f$search("")
$ if next .eqs. "" then goto done
$ diff 'next' /output =
$ goto loop
$done:

Well, you will have to do all error handling and other niceties yourself. I can eg thing of files with no lower version?

Please use HELP: after 25 years it still is MY friend!

Success.

Proost.

Have one on me.

jpe

Re: COM file to do DIFF

Hein van den Heuvel — Mon, 05 Feb 2007 09:57:39 GMT

Hi there,

Welcome to the HP ITRC OpenVMS forum.

Here is a script to get you going:

$loop:
$file = f$search("*.tmp;0",1)
$if file.eqs."" then exit
$older = f$elem(0,";",file) + ";-1"
$!write sys$output file, " ", older
$if "".eqs. f$search(older,2) then goto loop
$diff 'file
$goto loop

It does two 'fancy' things.

1) it uses special file version naming.
To get only the highest version of what might be many files it uses ";0" thus the script does not need to match for other files with the same name but different version. And to see whether a diff is needed it searches for version ;-1 that being the next older version if present.

2) it uses CONTEXT for F$SEARCH such that the main one used to loop through all the files, does nto get confused by the one to test for an older version

be sure to use VMS HELP on all construct in the exampel to fully comprehend.

$HELP LEXI F$SEARCH
$HELP LEXT F$ELEMENT
:

Enjoy DCL,
Hein van den Heuvel

Re: COM file to do DIFF

Joseph Huber_1 — Mon, 05 Feb 2007 10:04:00 GMT

Best would be to get one of the general "operate on a list of files" command-files from some freeware archive. The best IMHO is EACH.COM (on dcl.openvms.org ? , if not, my copy is at http://wwwvms.mppmu.mpg.de/util_root/com/each.com )
Then the stuff is rather easy:
$ EACH *.*;0 "DIFFERENCE 'n'"

But for a list of files, You probably want to do something with the files if they are (not-)identical:
some examples how to do things after comparisons are in my command-files like
DELETE_IF_IDENTICAL.COM
COPY_IF_DIFFERENT.COM
on the http page above.

Re: COM file to do DIFF

Hein van den Heuvel — Mon, 05 Feb 2007 22:10:40 GMT

Joseph is correct.
It is kinda nice to have a generic 'do this action for this list of files script'.

Also, John Gillings pointed out to me that the following line is too quick & dirty in my script:

$ older = F$PARSE(";-1",file) + ";-1"

The problem is of course files with ";" somewhere else in the name. And for other cases perhaps the usage of "." as version indicator. I frequently do things like: delete x.tmp.

The proper way to solve this with learning as little as possible about file name parsing yourself is:

$ older = F$PARSE(";-1",file)

Correct. And shorter :-)

Runner up might be:

older = file - f$parse(file,,,"version") + ";-1"

I only show that to show the power of string substractions and appends. The straight parse is better.

Cheers,
Hein.

Re: COM file to do DIFF

Joseph Huber_1 — Tue, 06 Feb 2007 05:04:57 GMT

By the way, EACH together with PIPE allows to do something like:

each *.com;-1 "pipe diff 'nt'/nooutput ; if $SEVERITY.eq.1 then delete/log 'nt';0"

to delete the newest identical versions of files.