diff --git a/topics/Week2_Best_Practices/challenge/btpguid b/topics/Week2_Best_Practices/challenge/btpguid
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+#!/bin/bash
+# btpguid - return BTP subaccount/directory GUIDs
+
+# Usage: btpguid [-t|--target] displayname
+
+# Returns the GUID for the given subaccount or directory, which is
+# specified by name. If the option -t or --target is specified, it
+# will also set that subaccount or directory as the target.
+
+# Requires the btp CLI. Will direct you to log in first if you're
+# not already logged in.
+
+# It uses the detail from the output of this command:
+# btp get accounts/global-account --show-hierarchy
+
+# Uses the "${2:-$1}" technique seen in fff - see
+# https://qmacro.org/autodidactics/2021/09/03/exploring-fff-part-1-main/
+# for details.
+
+gethier() {
+  btp get accounts/global-account --show-hierarchy 2> /dev/null
+}
+
+main() {
+
+  local hierarchy subtype guid displayname rc=0
+
+  displayname="${2:-$1}"
+
+  [[ -z $displayname ]] && {
+    echo "No display name specified"
+    exit 1
+  }
+
+  hierarchy="$(gethier)" || { btp login && hierarchy="$(gethier)"; }
+  read -r subtype guid <<< "$(grep -P -o "^(subaccount|directory)\s+(\S+)(?=\s+$displayname)" <<< "$hierarchy")"
+
+  # Set the subtype as target if requested
+  [[ $1 == -t ]] || [[ $1 == --target ]] && {
+    btp target "--${subtype}" "$guid" &> /dev/null
+    rc=$?
+  }
+
+  echo "$guid"
+  return $rc
+
+}
+
+main "$@"
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