diff --git a/cmd/cfg/main.go b/cmd/cfg/main.go
index 78047fc41c269ec9ef3407fa990bd3329fac3230..ccb142eef5410054bc4359e8af877717d7376604 100644
--- a/cmd/cfg/main.go
+++ b/cmd/cfg/main.go
@@ -1,9 +1,9 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
-	"io"
 	"os"
 	"path/filepath"
 	"strings"
@@ -40,27 +40,19 @@ 	if err := fs.Parse(os.Args[1:]); err != nil {
 		return err
 	}
 
+	if fs.NArg() < 1 {
+		return errors.New("cfg requires at least an input file")
+	}
+
 	cleanArg := func(arg string) string {
 		return strings.TrimPrefix(filepath.Ext(arg), ".")
 	}
 
-	in := os.Stdin
-	if fs.NArg() > 0 {
-		fi, err := os.Open(fs.Arg(0))
-		if err != nil {
+	in := fs.Arg(0)
+	if unmarshal == nil {
+		if err := fromFunc(cleanArg(fs.Arg(0))); err != nil {
 			return err
 		}
-		defer fi.Close()
-		in = fi
-
-		if unmarshal == nil {
-			if err := fromFunc(cleanArg(fs.Arg(0))); err != nil {
-				return err
-			}
-		}
-
-	} else if unmarshal == nil {
-		unmarshal = cfg.JSON.Unmarshal
 	}
 
 	out := os.Stdout
@@ -83,7 +75,7 @@ 	}
 
 	var data any
 
-	inData, err := io.ReadAll(in)
+	inData, err := os.ReadFile(in)
 	if err != nil {
 		return err
 	}