set CreateDate — if not defined

[c6y]

I'm trying to set CreateDate to the current date — but keep the original CreateDate, if already defined.

It's not working though, as the current date is always written, even if the file had a CreateDate already.

DATE=`date +%Y:%m:%d\ %H:%M:%S%z`
exiftool \
  -r \
  -all= \
  -CreateDate-= -CreateDate="$DATE" \
  -overwrite_original \
  .

Thanks!

[Hayo Baan]

Try this:

Code Select Expand

DATE=`date +%Y:%m:%d\ %H:%M:%S%z`
exiftool \
  -r \
  -all= \
  -CreateDate="$DATE" \
  "-CreateDate<CreateDate" \
  -overwrite_original \
  .

This will keep the original CreateDate if there was one and still remove all other metadata.

[Phil Harvey]

Unfortunately the "-=" is a shift operator for date/time tags, so you can't use it for a conditional replacement.  Instead, Hayo's suggestion is good, but you can simplify your script to just this:

exiftool -r -all= -createdate=now "-createdate<createdate" -overwrite_original .

(ExifTool understands the word "now" as a date/time value)

- Phil

[c6y]

Thanks Phil & Hayo. This works well!

Unfortunately it stops working when I add this line: -TagsFromFile @ -Software \. The result will always be that now is written to CreateDate. Why?

exiftool \
  -r \
  -TagsFromFile @ -Software \
  -all= \
  -createdate=now "-createdate<createdate" \
  -overwrite_original \
  .

[c6y]

instead, this is what preserves the Software tag (if available) — and writes the CreateDate correctly:

exiftool \
  -r \
  -all= \
  -createdate=now "-createdate<createdate" \
  "-software<software" \
  -overwrite_original \
  .

this is strange though: if the software command is written before the createdate command, it will again only use now for the createdate (and ignore copying the existing value)

Thanks again!

[Phil Harvey]

Order matters.  Anything assigned before -all= won't get written (because -all= deletes everything).  See FAQ 22 for an explanation.

But I think you may be confused about what happens if the software argument comes before the createdate one.  These two arguments are independent, so order shouldn't matter (unlike with -all=, which affects all tags).

- Phil