I want to keep data strings from being truncated or ignored.

[L_Carver]

Particularly, I'd like to avoid

Code Select Expand

Warning: [Minor] IPTC:ProgramVersion exceeds length limit errors and like messages when writing tags.

Upside: Quite a few versions/years back, I had to change a tag I regularly used with exiv2 because it had an ampersand (&) right in the middle. I tried the same tag on a JPEG file about five minutes ago, and it "took," i.e., the amp wasn't dropped neither was whitespace inserted in its place.

But back on the original topic. Is there anyplace I can find what the length limits of certain tags are? Like ProgramVersion, just to use one example.

Carver

[StarGeek]

Is there anyplace I can find what the length limits of certain tags are? Like ProgramVersion, just to use one example.

Check under the various tag groups pages but I think you'll mostly have this problem with IPTC data.  Make sure you read the info on the IPTC page.  You can override the line limitations with the -m option but it is possible to run into problems with programs that can't deal with the changes.

You could also look into using XMP tags, which don't have a length limitation AFAIK.