replace echo with printf for edge cases

driver.sh

@@ -2,21 +2,21 @@
 cd "$(dirname "$0")" || exit 1
 
 ok() {
-    echo "[OK]   $3"
+    printf '[OK]   %s\n' "$3"
 }
 
 warn() {
-    echo "[WARN] $3"
+    printf '[WARN] %s\n' "$3"
 }
 
 run_module() {
     set -eu
 
     . "$1"
-    echo "$name"
+    printf '%s\n' "$name"
 
     if [ "$available" -ne 1 ]; then
-        echo "not available"
+        printf 'not available\n'
         return
     fi
 
@@ -27,7 +27,7 @@ ls modules | while IFS= read -r module; do
     [ -f "modules/$module" ] || continue
     ( run_module "modules/$module" ) 
     if [ "$?" -ne 0 ]; then
-        echo "Error running module: $module"
+        printf 'Error running module: %s\n' "$module"
     fi
-    echo
+    printf '\n'
 done