Thanks to both of you, but I still get the same error.
desktop@desktop-desktop:~/pics$ gimp -i -b '(batch-resize "/pics/*.jpg" 500 500)' -b '(gimp-quit 0)'
batch command experienced an execution error:
Error: ( : 1) eval: unbound variable: batch-resize
desktop@desktop-desktop:~/pics$ gimp -i -b '(batch-resize "./pics/*.jpg" 500 500)' -b '(gimp-quit 0)'
batch command experienced an execution error:
Error: ( : 1) eval: unbound variable: batch-resize
and you can see I do have images in the directory:
desktop@desktop-desktop:~/pics$ ls
00001833.jpg 00001834.jpg 00001835.jpg
desktop@desktop-desktop:~/pics$
Also - post your address so I can pay.