Generate a hashcat rule file to prepend {username}: to every password

hashcat_gen_username_rule.sh

#!/bin/bash

usage() {
  cat <<EOF
Takes a list of usernames a writes a rule file to prepend each of these to each password canditate.

${BASH_SOURCE[0]} <options> <username or file> [<username or file> ...]

Options:
  -@       Also take the base username if full one is an email
  -t       Test the rules when done. Requires an output file
  -s CHAR  Append the given character (or string) after the username. Default is :
  -S CHAR  Split each input at the given character. Default is newline.
           If the input file contains passwords too, set this to the separator
  -o FILE  Save output to FILE. Default is stdout
EOF
  exit 1
}

print_array() {
  local IFS=$'\n' arr="${1}[*]" elem="$2"
  echo "${!arr}"
}

in_array() {
  local IFS=$'\n' arr="${1}[*]" elem="$2"
  print_array "$arr" | fgrep -qx "$elem"
}

add_uname() {
  local uname="${1%%${IN_SEP}*}"
  if ! in_array USERNAMES "$uname" ; then
    USERNAMES+=("$uname")
  fi
  if [ $DO_SPLIT -eq 1 -a "${uname/@/}" != "$uname" ] ; then
    add_uname "${uname%@*}"
  fi
}

add_unames_from_file() {
  local fname="$1" line
  while IFS= read line ; do
    add_uname "$line"
  done < "$fname"
}

process_unames() {
  local a
  for a in "$@" ; do
    if [ -f "$a" ] ; then
      add_unames_from_file "$a"
    else
      add_uname "$a"
    fi
  done
}

output_rules() {
  local u 
  print_array USERNAMES | sed "s/\$/${OUT_SEP}/" | rev \
    | sed 's/./ ^\0/g;s/^ //' > "$OUTPUT"
}

USERNAMES=()
ARGS=()
DO_SPLIT=0
DO_TEST=0
IN_SEP=$'\n'
OUT_SEP=:
OUTPUT=/dev/stdout

while [ $# -gt 0 ] ; do
  case "$1" in
    -@)
      DO_SPLIT=1
      ;;
    -t)
      DO_TEST=1
      ;;
    -o)
      OUTPUT="$2"
      shift
      ;;
    -s)
      OUT_SEP="$2"
      shift
      ;;
    -S)
      IN_SEP="$2"
      shift
      ;;
    -*)
      usage
      ;;
    *)
      ARGS+=("$1")
      ;;
  esac
  shift
done

process_unames "${ARGS[@]}"
output_rules

echo "Give this rule file as the first rule file to hashcat" >&2
if [ $DO_TEST -eq 1 -a -f "$OUTPUT" ] ; then
  echo -e "Testing:\n" >&2
  temp="$(mktemp)"
  echo test > "$temp"
  hashcat --stdout -r "$OUTPUT" "$temp"
  rm "$temp"
fi