Recipe to output duplicate files in a given directory...

dupes.sh

#!/usr/bin/env bash

# 1. create hashes only
# 2. sort so duplicate lines follow each other
# 3. output duplicated checksums (one of each)
# 4. rerun hash tool in matching mode to output duplicates paths and checksums

# Explain Shells...
# ES1: http://explainshell.com/explain?cmd=sha1deep+-q+-r+-s+%22%24DIR%22+%7C+sort+%7C+uniq+-d+%3E+%22%24temp_file%22
# ES2: http://explainshell.com/explain?cmd=sha1deep+-r+-s+-M+%22%24temp_file%22+%22%24DIR%22

set -o errexit
set -o pipefail
set -o nounset

DIR="$1"

temp_file=$(mktemp "/tmp/dupes.sh.tmp.XXXXXX")
sha1deep -q -r -s "$DIR" | sort | uniq -d > "$temp_file"   #ES1
sha1deep -r -s -M "$temp_file" "$DIR"   #ES2
rm ${temp_file}

Demo here: https://asciinema.org/a/96766