Problem with conditional writing

[MikeBlyth]

I'm sure I'm just missing something simple in syntax, but I'm not getting "write tag if empty" to work. If I use,

exiftool -description-="Napoleon" *.jpg

nothing happens.

On the other hand, if I write,

exiftool -description="Napoleon" -if "not $description" *.jpg

then the tag is updated. What am I doing wrong?

[StarGeek]

Your first example isn't conditional writing, it's conditional deletion.  From the docs:
"-= may be used to conditionally delete or replace a tag"

Instead, take a look at the -wm option.  From the docs there:
"use -wm cg to only create new tags (and avoid editing existing ones)."