--- a/shasum.py	Fri Dec 04 12:05:55 2020 +0100
+++ b/shasum.py	Fri Dec 04 12:37:29 2020 +0100
@@ -42,17 +42,17 @@
         sys.exit(78)   # :manpage:`sysexits(3)` EX_CONFIG
     if not opts.files:
         opts.files.append("-")
-    for fn in opts.files:
-        if fn == "-":
-            if PY2:
-                if sys.platform == "win32":
-                    import os. msvcrt
-                    msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
-                source = sys.stdin
-            else:
-                source = sys.stdin.buffer
-            print(compute_digest(hashlib.sha256, source))
+    if len(opts.files) == 1 and opts.files[0] == "-":
+        if PY2:
+            if sys.platform == "win32":
+                import os. msvcrt
+                msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
+            source = sys.stdin
         else:
+            source = sys.stdin.buffer
+        print(compute_digest(hashlib.sha256, source))
+    else:
+        for fn in opts.files:
             with open(fn, "rb") as source:
                 print(compute_digest(hashlib.sha256, source))