Copying multiple files to multiple directories

In bash, try the following code :

#!/bin/bash

c=0

for f; do
    if ! ((c % 100)); then
        folder=folder_$(printf "%03d\n" $c)
        mkdir -p $folder
    fi

    [[ -d "$f" ]] || mv "$f" "$folder"
    ((c++))
done

Run the script like that :

./script.bash *

Just add the base64 encoding of newline (Cg==) after each file name and pipe the whole thing to base64 -d:

find . -name "*_*" -printf "%f\n" |
  sed -n 's/_....-..-..\.pdf$/Cg==/p' |
  base64 -d

With your approach, that would have to be something like:

find . -name "*_*" -printf "%f\0" |
  sed -zn 's/_....-..-..\.pdf$//p' |
  xargs -r0 sh -c '
    for i do
      echo "$i" | base64 -d
    done' sh

as you need a shell to create those pipelines. But that would mean running several commands per file which would be quite inefficient.