Bash functions to: (1) visually compare two strings, and (2) compare a string with a computed SHA/MD5 checksum

comphash.sh

compstring () {
  STR_A_IN=$1
  STR_B_IN=$2
  STR_A_OUT=""
  STR_B_OUT=""
  POINTER=""
  LENGTH=${#STR_A_IN}
  if [ $# -lt 2 ] || [ -z $1  ]|| [ -z $2 ]; then
    echo "You must provide two strings to compare"
    return 1
  fi
  if [ $LENGTH -lt ${#STR_B_IN} ]; then echo less; fi
  if [ $LENGTH -lt ${#STR_B_IN} ]; then LENGTH=${#STR_B_IN}; fi
  if [[ $STR_A_IN == $STR_B_IN ]]; then
    STR_A_OUT=$STR_A_IN
    STR_B_OUT=$STR_B_IN
    POINTER="===== IDENTICAL\n"
  else
    for (( i=0; i<$LENGTH; i++ )); do
      if [[ ${STR_A_IN:$i:1} == ${STR_B_IN:$i:1} ]]; then
        STR_A_OUT+=${STR_A_IN:$i:1}
        STR_B_OUT+=${STR_B_IN:$i:1}
        POINTER+=" "
      else
        STR_A_OUT+="\033[1;7m${STR_A_IN:$i:1}\033[0m"
        STR_B_OUT+="\033[1;7m${STR_B_IN:$i:1}\033[0m"
        POINTER+="^"
      fi
    done
  fi
  echo
  echo $STR_A_OUT
  echo $STR_B_OUT
  echo $POINTER
}

comphash () {
  helptext () {
    echo "comphash - compare hashes"
    echo " "
    echo "comphash [options]"
    echo " "
    echo "options:"
    echo "-h, --help                show brief help"
    echo "-a, --algorithm=HASHCODE  specify hashing algorithm"
    echo "                            (defaults to md5)"
    echo "-c, --code=HASHCODE       specify hashcode to compare"
    echo "-f, --file=FILE           specify a file to check"
  }
  if ! test $# -gt 0; then
    helptext
    return 1
  fi
  ALGORITHM="md5"
  while test $# -gt 0; do
    case "$1" in
      -h|--help)
        helptext
        return 0
        ;;
      -a)
        shift
        if test $# -gt 0; then ALGORITHM=$1; fi
        shift
        ;;
      --algorithm*)
        export ALGORITHM=`echo $1 | sed -e 's/^[^=]*=//g'`
        shift
        ;;
      -c)
        shift
        if test $# -gt 0; then
          HASH_IN=$1
        else
          echo "no hash code specified"
          return 1
        fi
        shift
        ;;
      --code*)
        export HASH_IN=`echo $1 | sed -e 's/^[^=]*=//g'`
        shift
        ;;
      -f)
        shift
        if test $# -gt 0; then
          FILE=$1
        else
          echo "no file specified"
          return 1
        fi
        shift
        ;;
      --file*)
        FILE=`echo $1 | sed -e 's/^[^=]*=//g'`
        shift
        ;;
      *)
        break
        ;;
    esac
  done
  if [[ $ALGORITHM == "md5" ]]; then
    HASH_COMP=`md5 -q $FILE`
  elif [[ $ALGORITHM == "sha"* ]]; then
    HASH_COMP=`shasum -a $(echo $ALGORITHM | sed 's/sha//') $FILE | head -n1 | awk '{print $1;}'`
  else
    echo "'$ALGORITHM' not a valid algorithm"
    return 1
  fi
  compstring $HASH_IN $HASH_COMP
}