validate flags before reading stdin and reject bare -C with -j/-1/-2

main.go

@@ -357,22 +357,28 @@ func run(cfg config, nodeName, factName, match string, showRole, partial, invers
 		return nil
 	}
 
+	hasQuery := showRole || factName != ""
+	// Bare -C counts already-looked-up piped lines; only it needs stdin to validate.
+	bareCount := count && !hasQuery && !nodeOnly && !valueOnly && !ansible && !jsonMode && nodeName == ""
+	countErr := fmt.Errorf("-R or -F must be used with -1, -2, -C, or -A")
+
+	if (nodeOnly || valueOnly || (count && !bareCount) || ansible) && !hasQuery {
+		return countErr
+	}
+	if (match != "" || partial || inverse) && !hasQuery {
+		return fmt.Errorf("-R or -F must be used with -m, -p, or -i")
+	}
+
 	var reader *bufio.Reader
 	piped := false
 	if nodeName == "" {
 		reader, piped = stdinReader(os.Stdin)
 	}
-	// Bare -C on piped input counts the already-looked-up lines instead of querying.
-	passthrough := count && piped && !showRole && factName == ""
 
-	if (nodeOnly || valueOnly || (count && !passthrough) || ansible) && !showRole && factName == "" {
-		return fmt.Errorf("-R or -F must be used with -1, -2, -C, or -A")
-	}
-	if (match != "" || partial || inverse) && !showRole && factName == "" {
-		return fmt.Errorf("-R or -F must be used with -m, -p, or -i")
-	}
-
-	if passthrough {
+	if bareCount {
+		if !piped {
+			return countErr
+		}
 		var lines []string
 		scanner := bufio.NewScanner(reader)
 		for scanner.Scan() {