dupfind.sh

#!/bin/sh -e
# SUM is any command that produces following output:
#  <sum>  <file>
#SUM="md5 -r"
SUM="md5sum"

# F is output file for the list of files found by sumfiles
F=/tmp/dupfind.tmp

FINDPTH="."

#FINDPMS="-name '*.tar*' -type f"
FINDPMS="-type f"

sumfiles() {
  find $FINDPTH $FINDPMS -exec $SUM {} \;
}

listdupes() {
  cut -d" " -f1 | sort | uniq -d
}

printmatches() {
  while read sum
  do
    grep $sum $F
    echo
  done
}

sumfiles > $F
{ listdupes < $F; } | printmatches