mjhjmtu

At the moment I have a set of files of the form of:

/dir one/a picture.jpg
/dir two/some picture.jpg

What I want to do is copy and change the end to -fanart.jpg to the filename to:

/dir one/a picture.jpg
 /a picture-fanart.jpg
/dir two/some picture.jpg
 /some picture-fanart.jpg

I've managed to get it working for the situation where there are no spaces:

% for i in `find . -name "*.jpg"`; do cp $i "$i%.*"-fanart.jpg ;done;

but I to get it working where there are spaces.

Command substitution (`...` or $(...)) is split on newline, tab and space character (not only newline), and filename generation (globbing) is performed on each word resulting of that splitting. That's the split+glob operator. You could improve things by setting $IFS to newline and disable globbing, but here, best is to write it the proper way:

find . -name "*.jpg" -type f -exec sh -c '
 for i do
 cp "$i" "$i%.*-fanart.jpg"
 done' sh +

You could also use pax for that:

pax -rws'/.jpg$/-fanart&/' -s'/.*//' . .

Or zsh's zmv:

autoload zmv
zmv -QC '(**/)(*)(.jpg)(D.)' '$1$2-fanart$3'

Word expansion is performed during the expansion of unquoted command substitutions, which is why this does not work.

If you have bash4+, just use globstar:

shopt -s globstar
for file in **/*.jpg; do
 cp -- "$file" "$file%.*-fanart.jpg"
done