Replacing a string in XMP and IPTC metadata fields

[kennedyk]

We have a group of TIFF and PDF files to which I already appended metadata using the EXIF tool.  However, we now need to replace a string that appears in several parts of the metadata.  The string appears in the iptc:keywords, xmp:subject, iptc:source and xmp:source fields.  It is not the only keyword and it is part of a longer string in the source field.  We want everything to remain the same except for this string replacement.  We took at look at this previous posting (https://exiftool.org/forum/index.php/topic,8056.msg41200.html#msg41200) but this situation is a little different.

To give more context, here is the contents of that .bat file we used to append the metadata:

exiftool
-creator=
-title=
-description=
-copyright=
-make="Bookeye"
-model="3"
"-creator=Digitized by MIT Libraries Scanning Lab"
"-iptc:source=MIT Bulletin 2004-2005, volume 140, number 1, Collection AC0586, Massachusetts Institute of Technology, Institute Archives and Special Collections, Cambridge, MA"
"-xmp:source=MIT Bulletin 2004-2005, volume 140, number 1, Collection AC0586, Massachusetts Institute of Technology, Institute Archives and Special Collections, Cambridge, MA" "-iptc:keywords+=39080024066331"
"-xmp:subject+=39080024066331"
"-iptc:keywords+=MIT"
"-xmp:subject+=MIT"
"-iptc:keywords+=course catalogs"
"-xmp:subject+=course catalogs"
"-iptc:keywords+=AC0586"
"-xmp:subject+=AC0586"
"-transmissionreference=2017.004RR"
-m -r -ext .TIF -overwrite_original -ext .PDF %1

AC0586 is what needs to be replaced. 

Does anyone have any ideas of how to go about this?  Thanks in advance for your help! 

[StarGeek]

Test this command to see if it work for you.  Replace New String with your replacement text.

exiftool -api "Filter=s/AC0586/New String/" -tagsfromfile @ -iptc:keywords -xmp:subject -iptc:source -xmp:source FileOrDir

This will rewrite every file even if there isn't a change.  But since your Bat file includes the AC0586 for every file, I would think that every file would have it.  If this isn't the case, you can add this to the above command to process only files that would be changed.
-if "$iptc:keywords# ne $iptc:keywords or $xmp:subject# ne $xmp:subject or $iptc:source# ne $iptc:source or $xmp:source# ne $xmp:source"

[kennedyk]

That works!  Thank you so much!