sced: made it better?

.config/shell/bin/sced

@@ -1,21 +1,25 @@
-#!/bin/bash
+#!/bin/sh
 # sced (script edit) edit a script or function that's somewhere inside the shell configuration
 # Usage: bined <script name>
 # Depends: fd
 
+set -eu
+
+above_dir="$(dirname "$(realpath "$0")")"/..
+
 # start in the directory above the script
-cd "$(dirname "$(realpath "$0")")"/.. || exit 1
+cd "$above_dir"
 
 # get the path to the file if there was an argument
 if [ -n "$1" ]; then
-  FILE="$(fd --exact-depth 2 --max-results=1 -at f "$1")"
-  if [ "$FILE" = '' ]; then
-    FILE="$(dirname "$(realpath "$0")")/../$1"
+  file="$(fd --exact-depth 2 --max-results=1 -at f "$1")"
+  if [ -z "$file" ]; then
+    file="$(dirname "$(realpath "$0")")/../$1"
   fi
 else
   # edit >this< script by default
-  FILE="$(realpath "$0")"
+  file="$(realpath "$0")"
 fi
 
 # edit the file
-"${EDITOR:-$(which nvim)}" "${FILE:-$(realpath "$0")}"
+eval "${EDITOR:-$(which nvim)} ${file:-$(realpath "$0")}"