Quick bash script to generate a gravatar.com URL for a provided email address. Drop in your PATH and `chmod u+x`.

gravatar.sh

#!/usr/bin/env bash
# Generate the correct Gravatar URL for the provided email address.
# When the -o option is provided, `open` the URL in your default browser.

usage() { >&2 echo "Usage: ${0##*/} [-o] <email>"; exit 1; }

GRAVATAR_BASE_URL="https://gravatar.com/avatar/"
GRAVATAR_OPTIONS="d=wavatar"

# Parse command line arguments.
while getopts "oh" OPT; do
  case "$OPT" in
    o) OPEN_URL=true ;;
    *) usage ;;
  esac
done
shift $((OPTIND - 1))

# Ensure the email address is provided.
if [ -z "$1" ]; then
  >&2 echo "Error: A single email address is required."
  usage
fi

# Generate the Gravatar URL.
EMAIL_HASH=$(echo -n "$1" | tr '[:upper:]' '[:lower:]' | sha256)
GRAVATAR_URL="${GRAVATAR_BASE_URL}${EMAIL_HASH}?${GRAVATAR_OPTIONS}"

# Output the Gravatar URL.
echo "$GRAVATAR_URL"

# If the -o flag is set, open the URL in the default browser.
if [ "$OPEN_URL" = true ]; then
  open "$GRAVATAR_URL"
fi

zzz_chatgpt_gravatar.sh

#!/bin/bash DON'T USE THIS VERSION! ONLY FOR COMPARISON.

# Prompt provided to ChatGPT 4.0:
# Please produce a bash shell script that accepts an optional "-o" argument and a required email address as command line arguments, and outputs the correct gravatar URL for the provided email address. When the "-o" option is present, also use the MacOS "open" command to open the URL in the user's default browser.

# Errors:
#   - `/bin/bash` isn't guaranteed to be present on all versions of all typical operating systems. `/usr/bin/env bash` tends to be more broadly reliable because it'll inherit the current user's full $PATH.
#   - The script flat out fails without an initial `-o` option, because it assumes the email address is always in `$2`.
#   - According to [the Gravatar docs](https://docs.gravatar.com/api/avatars/hash/), the email should be hashed using SHA256, not MD5. (Although it does appear URLs employing md5 still function.)
#   - The supplied "acceptable options" to `getopts` is `'o'`, even though there is a catch-all `*` case for displaying usage. This means getopts outputs a warning about an unrecognized option even for `gravatar.sh -h` formulation.
#   - The whole `get_gravatar_url` function would be good abstraction in a full fledged program, but for a legitimately simple bash script it's needless misdirection. (Compare to my above version.)
#   - Usage output is NOT well abstracted into a reusable function, nor does it print to STDERR.
#   - The usage text also typically truncates `$0` to just the basename via `${0##*/}` instead of revealing the whole filesystem path to the executable.

# ---

# Function to calculate the MD5 hash of the email address
get_gravatar_url() {
  local email=$1
  local hash=$(echo -n "$email" | tr '[:upper:]' '[:lower:]' | md5)
  echo "https://www.gravatar.com/avatar/$hash"
}

# Check if no email address is provided
if [ -z "$2" ]; then
  echo "Usage: $0 [-o] <email>"
  exit 1
fi

# Parse options
OPEN=false
while getopts "o" opt; do
  case $opt in
    o)
      OPEN=true
      ;;
    *)
      echo "Usage: $0 [-o] <email>"
      exit 1
      ;;
  esac
done

# Email is the last argument after options
EMAIL="${@:$OPTIND:1}"

# Get the Gravatar URL for the provided email
GRAVATAR_URL=$(get_gravatar_url "$EMAIL")
echo "Gravatar URL: $GRAVATAR_URL"

# If -o option is set, open in browser
if [ "$OPEN" = true ]; then
  open "$GRAVATAR_URL"
fi