Write IPTC "byline" to all images within a folder

[davidlab]

I am new to the Exiftool and I have been researching for what I need, but can't seem to find exactly what I am trying to do.
I have a folder images and I need to add IPTC "byline" meta to them. They will all have the same 'byline'.
Also, not sure if Exiftool can do this but I would like it so when new images are added to that folder the IPTC "byline" tag is automatically written.
I am on a mac.
Thanks for any help you can provide.

[davidlab]

If I do this:
exiftool -iptc:By-line='mybyline' /Users/username/Desktop/foldername

It works, but also creates or renames the originals that I would like to remove during the process?

I also was thinking it would be great if I can capture the folder name that the images are in and add that name to the IPTC 'byline' .
Example: imagesfolder/{images} , then make exiftool read the folder name of the image (in this case 'imagesfolder') and add that to the IPTC 'byline'
exiftool -iptc:By-line='imagesfolder' /Users/username/Desktop/imagesfolder

Also, as I mentioned above I was wondering if there is a way to make this automatic when new images are added to the folder?

[StarGeek]

It works, but also creates or renames the originals that I would like to remove during the process?

Add -overwrite_original to avoid creating backups or use -delete_original to delete them when you're sure you don't need them anymore.

I also was thinking it would be great if I can capture the folder name that the images are in and add that name to the IPTC 'byline' .

Previous similar question using advanced formatting.

To put it all together, try something like this:
exiftool -overwrite_original  -iptc:By-line='mybyline ${directory;my @a=split m(/);$_=$a[-1]}' /Users/username/Desktop/foldername

Also, as I mentioned above I was wondering if there is a way to make this automatic when new images are added to the folder?

Exiftool doesn't have the ability to do this by itself.  You'll have to look into making a script or something similar to do this.