Break down a large folder into multiple subfolders by sequential names

Question

I have a folder with 20000 files in it. I need to split it into subfolders with increasing directory name (dir_1, dir_2....) with each folder having 500 files each in such a way that for example if files are from file_1.png to file_20000, the first folder should contain first 500 files i.e., file_1 to file 500 and immediate folder should contain files in a continued manner i.e, file_501 to file_1000 and so on.

Answer 1

#!/bin/sh

files_per_dir=500

set -- file_*

printf 'There are %d files\n' "$#"
printf 'Putting %d files in each new directory\n' "$files_per_dir"

N=0 # directory counter
n=0 # file counter

for filename do

    if [ "$(( n % files_per_dir ))" -eq 0 ]; then
        N=$(( N + 1 ))
        dir="dir_$N"
        printf 'Creating directory %s\n' "$dir"
        # mkdir "$dir"
    fi

    n=$(( n + 1 ))

    printf 'Moving %s to %s\n' "$filename" "$dir"
    # mv -i -- "$filename" "$dir"

done

The above would put 500 files into each directory (the actual commands that changes things have been commented out for safety). The filenames are assumed to match file_* and each new directory will be called dir_N where N is a positive integer.

If you want to move the files based on their numerical names (the above sorts the files in lexicographical order), then use

printf 'Moving %s to %s\n' "file_$n" "$dir"
# mv -i -- "file_$n" "$dir"

instead (i.e. replace the corresponding two lines in the first script with these, in this order).

---

Shortened version:

#!/bin/sh

files_per_dir=500

set -- file_*

n=0

for filename do
    n=$(( n + 1 ))

    N=$(( (n/files_per_dir) + 1 ))
    [ ! -d "dir_$N" ] && mkdir "dir_$N"

    # mv -i -- "$filename" "dir_$N"
    # or...
    # mv -i -- "file_$n" "dir_$N"
done

Answer 2

cd lotsafiles
for i in {1..20000}; do
  dirnum="$(((i/500)+1))"
  mkdir -p "dir_${dirnum}" # using -p allows this to be less noisy on repeat runs
  mv "file${i}.png" "dir_${dirnum}"/
done

Answer 3

Something simple along the lines of:

#!/bin/bash
typeset -i i
typeset -i j
typeset -i k

i=0
j=0
k=0
mkdir dir_$j
for file in * ; do
   i=$i+1
   k=$k+1
   if [ $i = 500 ] ; then
       j=$j+1
       i=0
       mkdir  dir_$j
   fi
   mv "$file" dir_$j/file_$k
done

Not tested, so you might put an echo in front of the mv "$file" dir_$j to see if it does what you want. Anyway it will give you an idea of how to do what you want.