Prevent overwriting existing tags

[Archive]

[Originally posted by djeyewater on 2010-01-04 15:11:17-08]

When using -tagsfromfile is it possible to only write tags that don't exist, and leave existing tags as they are?

Thanks

Dave

[Archive]

[Originally posted by exiftool on 2010-01-04 16:14:49-08]

The technique for doing this is not very intuitive and not
well documented, but basically what you want to do is use
the same technique as you would if you wanted to replace
only a specific value:

Code:

exiftool -artist-=you -artist=me image.jpg

but in your case you want to replace the tag only if the
previous value was empty:

Code:

exiftool -artist-= -artist=me image.jpg

I think this should do what you want.

- Phil

[Archive]

[Originally posted by bogdan on 2010-01-04 18:10:09-08]

Hi Phil,

You have amazed me again! Above solution deserves to be documented -nobody can "guess" that. Anyway, I'll write it down in my private Exiftool Examples file.

Thank you for being here.

Bogdan

[Archive]

[Originally posted by exiftool on 2010-01-04 18:22:42-08]

Actually, one of the WRITING EXAMPLES in the application
documentation gives an example of this, but this is the only
place I think it is mentioned.

[Archive]

[Originally posted by djeyewater on 2010-01-04 20:22:02-08]

Thanks for the info, I tried with

Code:

exiftool.pl -tagsfromfile src.jpg -all:all-= dst.jpg

but got the same results as I did before (i.e. existing tags were overwritten), so I guess this is just suitable for individual tags?

Thanks

Dave

[Archive]

[Originally posted by bogdan on 2010-01-04 21:24:05-08]

Now I'm really curious... using "-tagsfromfile", I have tried several possible combinations and it doesn't work -that is, if at all, it overwrites all tags.

I'm ready to be surprised

Bogdan

[Archive]

[Originally posted by exiftool on 2010-01-05 02:21:25-08]

Dave: Yes, it only works with individual tags.

Bogdan: Be surprised -- This is one of the subtleties mentioned for
-tagsFromFile (by default any copied tag will override all previous
assignments for the same tag).  So for this to work you must use
-addTagsFromFile instead.  (Yes, I know it is complicated.)

- Phil