How to move 100 files from a folder containing thousands?

for file in $(ls -p | grep -v / | tail -100)
do
mv $file /other/location
done

That assumes file names don't contain blanks, newline (assuming the default value of $IFS), wildcard characters (?, *, [) or start with -.

It's easiest in zsh:

mv -- *([1,100]) /other/location/

This moves the first 100 non-hidden files (of any type, change ([1,100]) to (.[1,100]) for regular files only, or (^/[1,100]) for any type but directory) in name lexicographic order. You can select a different sort order with the o glob qualifier, e.g. to move the 100 oldest files:

mv -- *(Om[1,100]) /other/location/

With other shells, you can do it in a loop with an early exit.

i=0
for x in *; do
  if [ "$i" = 100 ]; then break; fi
  mv -- "$x" /other/location/
  i=$((i+1))
done

Another portable way would be to build the list of files and remove all but the last 100.

If you're not using zsh:

set -- *
[ "$#" -le 100 ] || shift "$(($# - 100))"
mv -- "$@" /target/dir

Would move the last (in alphabetical order) 100 ones.