flatten leaf dirs

flatten.sh

#!/usr/bin/env bash
#
# SCRIPT: flatten.sh
# AUTHOR: janos <janos@MacBook-Pro.fritz.box>
# DATE:   2026-05-16
#
# PLATFORM: Not platform dependent
#
# PURPOSE: Flatten deeply nested leaf folders into numeric folders
#          named NNN at the base level.
#

set -euo pipefail

usage() {
    local exitcode=0
    if [ $# != 0 ]; then
        echo "$*" >&2
        exitcode=1
    fi
    cat << EOF
Usage: $0 [OPTION]... [ARG]...

Flatten deeply nested leaf folders into numeric folders named NNN at the base level.

Options:
  -t, --tabular          default = $tabular

  -d, --dry-run          default = $dry_run
      --no-dry-run       default = ! $dry_run
  -y, --yes              default = ! $dry_run

  -h, --help             Print this help

EOF
    exit "$exitcode"
}

args=()
dry_run=on
tabular=off
no_ds=off
nonleafs=off
while test $# != 0; do
    case $1 in
    -h|--help) usage ;;
    -d|--dry-run) dry_run=on ;;
    --no-dry-run|-y|--yes) dry_run=off ;;
    -t|--tabular) tabular=on ;;
    --no-ds) no_ds=on ;;
    --nonleafs) nonleafs=on ;;
    --) shift; while test $# != 0; do args+=("$1"); shift; done; break ;;
    -|-?*) usage "Unknown option: $1" ;;
    *) args+=("$1") ;;  # script that takes multiple arguments
    esac
    shift
done

set -- "${args[@]}"  # save arguments in $@

fatal() {
    echo >&2 "Fatal: $*"
    exit 1
}

cmd() {
    echo "+ $*"
    test "$dry_run" = off || return 0
    "$@"
}

countdir() {
    local count=$1
    test "$count" -le 999 || fatal "Too many directories: $count"
    printf "%03d" "$count"
}

find_count() {
    local basedir=$1
    local i
    for ((i = 1; i < 1000; ++i)); do
        if ! test -d "$basedir/$(countdir "$i")"; then
            echo "$i"
            return
        fi
    done
    fatal "Too many directories: $i"
}

find_leaf_dirs() {
    local basedir=$1
    find "$basedir" \
        -depth \
        -type d \
        ! -empty \
        | awk '!p || p !~ "^" $0 "/"; { p=$0 }' \
        | sort
}

flatten() {
    local basedir=$1
    local count leafdir

    count=$(find_count "$basedir")

    find_leaf_dirs "$basedir" | while IFS= read leafdir; do
        if [[ $leafdir == $basedir/[0-9][0-9][0-9] ]]; then
            continue
        fi
        cmd mv "$leafdir" "$basedir/$(countdir "$count")"
        ((++count))
    done
}

flatten_all() {
    for basedir; do
        flatten "$basedir"
    done
}

tabular() {
    sed -e 's?^\+ mv work/??' -e 's? work/?\t?'
}

no_ds() {
    cmd find "$@" -name .DS_Store -delete
}

find_nonleaf_dirs_with_files() {
    find "$@" -depth -type d ! -empty | while IFS= read path; do
        d=0
        f=0
        for p in "$path"/*; do
            if test -f "$p"; then
                ((++f))
            elif test -d "$p"; then
                ((++d))
            else
                fatal "unknown type: $p"
            fi
        done

        if ((d > 0 && f > 0)); then
            echo "$path"
        fi
    done
}

main() {
    if test "$tabular" = on; then
        tabular
    elif test "$no_ds" = on; then
        no_ds "$@"
    elif test "$nonleafs" = on; then
        find_nonleaf_dirs_with_files "$@"
    else
        flatten_all "$@"
    fi
}

main "$@"