List all leaf subdirectories in linux

The solution using awk is nice, simple… and fails if the directory name contains any character that is considered special in forming regex patterns. This also presents an issue with the ~ or != tests in Bash.

The following seems to work for both BSD and GNU find:

find . -type d | sed 's:$:/:' | sort -r | while read -r dir;do [[ "${dir}" != "${prev:0:${#dir}}" ]] && echo "${dir}" && prev="${dir}”;done

• Change find . to any directory you want to start the search in.
• The sed command adds a forward slash to each directory returned by find.
• sort -r sorts the directory list in reverse alphabetical order, which has the benefit of listing the directories furthest away from a root first, which is what we want.
• This list is then read in line-by-line by the while read loop, where the -r option further protects against treating certain characters differently from others.
• We then need to compare the current line against the previous one. As we cannot use the != test and that intermediate directories will have a path shorter than that of the corresponding leaf directory, our test will compare the current line to the previous line truncated to the length of the current line. If that’s a match, then we can discard this line as a non-leaf directory, otherwise we print this line and set it as the previous line ready for the next iteration. Note that the strings need to be quoted in the test statement, otherwise some false positives may be produced.

Oh, if you don’t want to use find…

shopt -s nullglob globstar;printf "%s\n" **/ | sort -r | while read -r dir;do [[ "${dir}" != "${prev:0:${#dir}}" ]] && echo "${dir}" && prev="${dir}";done;shopt -u nullglob globstar

UPDATE (2020-06-03): Here’s a script I’ve thrown together that’s hopefully useful. Obviously feel free to improve/adapt/point out glaring problems…

#!/usr/bin/env bash

# leaf: from a given source, output only the directories
#       required ('leaf folders' ) to recreate a full
#       directory structure when passed to mkdir -p 

usage() {
    echo "Usage: ${0##*/} [-f|-g|-h|-m <target>|-s|-S|-v] <source>" 1>&2
}

# Initial variables...
dirMethod=0 # Set default method of directory listing (find -d)
addSource=0 # Set default ouput path behaviour

# Command options handling with Bash getopts builtin
while getopts ":fghm:sSv" options; do
    case "${options}" in
        f) # use depth-first find method of directory listing
            dirMethod=0 # set again here if user sets both f and g
            ;;
        g) # Use extended globbing and sort method of directory listing
            dirMethod=1
            ;;
        h) # Help text
            echo "Leaf - generate shortest list of directories to (optionally)"
            echo "       fully recreate a directory structure from a given source"
            echo 
            echo "Options"
            echo "======="
            usage
            echo
            echo "Directory listing method"
            echo "------------------------"
            echo "-f           Use find command with depth-first search [DEFAULT]"
            echo "-g           Use shell globbing method"
            echo
            echo "Output options"
            echo "--------------"
            echo "-m <target>  Create directory structure in <target> directory"
            echo "-v           Verbose output [use with -m option]"
            echo "-s           Output includes source directory"
            echo "-S           Output includes full given path of <source> directory"
            echo
            echo "Other options"
            echo "-------------"
            echo "-h           This help text"
            exit 0 # Exit script cleanly
            ;;
        m) # make directories in given location
            destinationRootDir="${OPTARG}"
            ;;
        s) # Include source directory as root of output paths/tree recreation
            addSource=1
            ;;
        S) # Include full source path as root of output paths/tree recreation
            addSource=2
            ;;
        v) # Verbose output if -m option given
            mdOpt="v"
            ;;
        *) # If no options... 
            usage
            exit 1 # Exit script with an error
            ;;
    esac
done
shift $((OPTIND-1))

# Positional parameters handling - only one (<source>) expected
if (( $# == 1 )); then
    if [[ $1 == "/" ]]; then # Test to see if <source> is the root directory /
        (( dirMethod == 0 )) && sourceDir="${1}" || sourceDir=
            # Set sourceDir to '/' if using find command dir generation or null if bash globbing method
    else
        sourceDir="${1%/}" # Strip trailing /
    fi
else
    usage  # Show usage message and...
    exit 1 # Quit with an error
fi

# Generate full pre-filtered directory list depending on requested method
if (( dirMethod == 0 )); then # find command method
    dirList=$(find "${sourceDir}" -depth -type d 2>/dev/null | sed -e 's:^/::' -e '/^$/ ! s:$:/:')
        # find command with depth-first search should eliminate need to sort directories
        # sed -e 's:^/::' -e '/^$/ ! s:$:/:' - strip leading '/' if present and add '/'
        #                                      to all directories except root
else
    shopt -s nullglob globstar dotglob
    # nullglob - don't return search string if no match
    # globstar - allow ** globbing to descend into subdirectories. '**/' returns directories only
    # dotglob  - return hidden folders (ie. those beginning with '.') 
    dirList=$(printf "%s\n" "${sourceDir}"/**/ | sed -e 's:^/::' | sort -r)
    # sort command required so filtering works correctly
fi

# Determine directory stripping string. ie. if given path/to/source[/] as the
# source directory (src), should the output be just that of the contents of src,
# src and its contents or the path/to/src and contents?
sourceDir="${sourceDir#/}"
case "${addSource}" in
    0) strip="${sourceDir}/";; # Set 'strip' to <source> 
    1) [[ "${sourceDir}" =~ (\/?.+)\/.+$ ]] && strip="${BASH_REMATCH[1]}/" || strip="/"
       # To strip down to <source> only, check to see if matched by regex and only return matched part
       # If not found, behave like -S
       ;;
    2) strip="/";; # Set 'strip' to nothing but a forward slash
esac

# Main loop
# Feed the generated dirList into this while loop which is run line-by-line (ie. directory by directory)
while read -r dir;do
    if [[ "${dir}" != "${prev:0:${#dir}}" ]]; then
        # If current line is not contained within the previous line then that is a valid directory to display/create 
        if [[ -v destinationRootDir ]]; then # If destinationRootDir is set (-m) then create directory in <target>
            mkdir -p${mdOpt} "${destinationRootDir%/}/${dir#$strip}"
            # -p - create intermediate directories if they don't exist. The filtered list means no unnecessary mkdir calls
            # if mdOpt is set, it is 'v', meaning mkdir will output each created directory path to stdin
            # ${dir#$strip} removes the set strip value from the line before it is displayed/created
        else
            echo "${dir#$strip}" # Same as above but no directories created. Displayed only, so -v ignored here
        fi
        prev="${dir}" # Set prev to this line before the loop iterates again and the next line passed to dir
    fi
done <<<"${dirList}" # This is a here string

On most filesystems (not btrfs), the simple answer is:

find . -type d -links 2

In https://unix.stackexchange.com/questions/497185/how-to-find-only-directories-without-subdirectories there is a solution that works on btrfs, but it's unbearably ugly:

find . -type d \
    \( -exec sh -c 'find "$1" -mindepth 1 -maxdepth 1 -type d -print0 | grep -cz "^" >/dev/null 2>&1' _ {} \; -o -print \)

There's an alternative to find called rawhide (rh) that makes this much easier:

rh 'd && "[ `rh -red %S | wc -l` = 0 ]".sh'

A slightly shorter/faster version is:

rh 'd && "[ -z \"`rh -red %S`\" ]".sh'

The above commands search for directories and then list their sub-directories and only match when there are none (the first by counting the number of lines of output, and the second by checking if there is any output at all per directory).

If you don't need support for btrfs, it's more like find but still shorter:

rh 'd && nlink == 2'

For a version that works on all filesystems as efficiently as possible:

rh 'd && (nlink == 2 || nlink == 1 && "[ -z \"`rh -red %S`\" ]".sh)'

On normal (non-btrfs) filesystems, this will work without the need for any additional processes for each directory, but on btrfs, it will need them. This is probably best if you have a mix of different filesystems including btrfs.

Rawhide (rh) is available from https://raf.org/rawhide or https://github.com/raforg/rawhide. It works at least on Linux, FreeBSD, OpenBSD, NetBSD, Solaris, macOS, and Cygwin.

Disclaimer: I am the current author of rawhide