This is probably quite easy, but I can't figure it out. In a for loop I want to exclude certain files with the prefix zz (e.g. zz131232.JPG) but I don't know how to exclude these files.
for i in *.JPG; do
# do something
done
How do I modify the 'for rule' to exclude files with the prefix zz?
Something like
for i in *.JPG; do
[[ $i != "zz"* ]] && echo "$i"
done
or skip them:
for i in *.JPG; do
[[ $i == "zz"* ]] && continue
# process the other files here
done
If you are dealing with many files you can also use GLOBIGNORE or extended globbing to avoid expanding the files you wish to skip in the first place (which might be faster):
GLOBIGNORE='zz*'
for file in *.JPG; do
do_something_with "${file}"
done
# save and restore GLOBIGNORE if necessary
or
shopt -s extglob # enable extended globbing
for file in !(zz*).JPG; do
do_something_with "${file}"
done
shopt -u extglob # disable extended globbing, if necessary
Note that if there are no .JPG files in the current directory the loop will still be entered and $i be set to the literal *.JPG (in your example), so you either need to check if the file exists inside the loop or use the nullglob option.
for file in *.JPG; do
[ -e "${file}" ] || continue
do_something_with "${file}"
done
or
shopt -s nullglob
for file *.JPG; do
do_something_with "${file}"
done
shopt -u nullglob # if necessary
Try the following in your shell to understand what happens without nullglob:
$ for f in *.doesnotexist; do echo "$f"; done
*.doesnotexist