sort-cli: rework

sort-cli/loader.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"io"
+	"log"
+	"os"
+)
+
+func open(sources []string) io.Reader {
+	rs := make([]io.Reader, 0, len(sources))
+
+	for _, source := range sources {
+		var r io.Reader
+
+		if source == "-" {
+			r = os.Stdin
+		} else {
+			if _, err := os.Stat(source); err != nil {
+				log.Fatalf("file not exists: %s", source)
+			}
+
+			f, err := os.Open(source)
+			if err != nil {
+				log.Fatalf("file open file: %s", err)
+			}
+
+			r = f
+		}
+
+		rs = append(rs, r)
+	}
+
+	return io.MultiReader(rs...)
+}