Bash script to split the current directory into N sub directories each with a set number of files.

split_folder.sh

# split_folder
# 
# Usage:
# split_folder NumberOfFilesPerFolder FileType 
#
# Example:
# split_folder 100 "*.jpg"
# split_folder 250 "*.NEF"

function split_folder {

    #Optional Positional Arguments
    N_FILES=${1:-100}                   # Number of files you want in each folder.
    FILES=${2:-"*.*"}                 # Filetype, accepts any string.

    let m=0                             # Loop vairable.
    let M=0                             # Folder name variable.

    for i in $FILES; do

        let m=$m+1
        if [ $m -gt $N_FILES ]; then    # Reset loop variable. Increment folder name.
            let m=0
            let M=$M+1
        fi

        if [ ! -d "$M" ]; then          # Create the folder if it doesn't exist.
            echo "Creating $M"
            mkdir "$M"
        fi

        mv "$i" "$M"                    # Move this file.
    done

    echo "Done"                         # Done.
}