diff --git a/pkg/interp/bufferrange.go b/pkg/interp/bufferrange.go
index 8e6d5ff69..fad0e463c 100644
--- a/pkg/interp/bufferrange.go
+++ b/pkg/interp/bufferrange.go
@@ -88,25 +88,27 @@ func (of *openFile) ToBufferView() (BufferRange, error) {
 // TODO: when to close? when bb loses all refs? need to use finalizer somehow?
 func (i *Interp) _open(c interface{}, a []interface{}) interface{} {
 	var err error
-
+	var f fs.File
 	var path string
-	path, err = toString(c)
-	if err != nil {
-		return fmt.Errorf("%s: %w", path, err)
-	}
 
-	var bEnd int64
-	var f fs.File
-	if path == "" || path == "-" {
+	switch c.(type) {
+	case nil:
+		path = "<stdin>"
 		f = i.os.Stdin()
-	} else {
+	default:
+		path, err = toString(c)
+		if err != nil {
+			return fmt.Errorf("%s: %w", path, err)
+		}
 		f, err = i.os.FS().Open(path)
 		if err != nil {
 			return err
 		}
 	}
 
+	var bEnd int64
 	var fRS io.ReadSeeker
+
 	fFI, err := f.Stat()
 	if err != nil {
 		f.Close()
diff --git a/pkg/interp/funcs.jq b/pkg/interp/funcs.jq
index e746feb38..2b1e8d012 100644
--- a/pkg/interp/funcs.jq
+++ b/pkg/interp/funcs.jq
@@ -1,11 +1,3 @@
-def print: stdout;
-def println: ., "\n" | stdout;
-def debug:
-  ( ((["DEBUG", .] | tojson), "\n" | stderr)
-  , .
-  );
-def debug(f): . as $c | f | debug | $c;
-
 def display($opts): _display(options($opts));
 def display: display({});
 def d($opts): display($opts);
diff --git a/pkg/interp/internal.jq b/pkg/interp/internal.jq
index 628693750..3ca755165 100644
--- a/pkg/interp/internal.jq
+++ b/pkg/interp/internal.jq
@@ -1,3 +1,12 @@
+# is here to be defined as early as possible to allow debugging
+def print: stdout;
+def println: ., "\n" | stdout;
+def debug:
+  ( ((["DEBUG", .] | tojson), "\n" | stderr)
+  , .
+  );
+def debug(f): . as $c | f | debug | $c;
+
 def _global_var($k): _global_state[$k];
 def _global_var($k; f): _global_state(_global_state | .[$k] |= f) | .[$k];
 
diff --git a/pkg/interp/interp.jq b/pkg/interp/interp.jq
index 6990cf165..b47bbd355 100644
--- a/pkg/interp/interp.jq
+++ b/pkg/interp/interp.jq
@@ -36,8 +36,9 @@ def input:
     | _input_filename(null) as $_
     | $h
     | try
+        # null input here means stdin
         ( open
-        | _input_filename($h) as $_
+        | _input_filename($h // "<stdin>") as $_
         | .
         )
       catch
@@ -233,10 +234,12 @@ def _main:
             ),
             expr_eval_path: $combined_opts.expr_file,
             filenames: (
-              ( if $combined_opts.expr_file then $rest
+              ( if $combined_opts.filenames then $combined_opts.filenames
+                elif $combined_opts.expr_file then $rest
                 else $rest[1:]
                 end
-              | if . == [] then null end
+              # null means stdin
+              | if . == [] then [null] end
               )
             ),
             join_string: (
@@ -291,10 +294,12 @@ def _main:
     elif $opts.show_formats then
       _formats_list | println
     elif
-      ( ($rest | length) == 0 and
+      ( $opts.filenames == [null] and
+        $opts.null_input == false and
         ($opts.repl | not) and
         ($opts.expr_file | not) and
-        $stdin.is_terminal and $stdout.is_terminal
+        $stdin.is_terminal and
+        $stdout.is_terminal
       ) then
       ( (( _usage($arg0), "\n") | stderr)
       , null | halt_error(_exit_code_args_error)
diff --git a/pkg/interp/options.jq b/pkg/interp/options.jq
index 052bc8a65..48cc7ee1f 100644
--- a/pkg/interp/options.jq
+++ b/pkg/interp/options.jq
@@ -34,9 +34,9 @@ def _opt_build_default_fixed:
       decode_progress: (env.NO_DECODE_PROGRESS == null),
       depth:           0,
       expr:            ".",
-      expr_file:       null,
       expr_eval_path:  "arg",
-      filenames:       ["-"],
+      expr_file:       null,
+      filenames:       null,
       include_path:    null,
       join_string:     "\n",
       null_input:      false,
@@ -108,14 +108,14 @@ def _opt_cli_arg_options:
       color:           (.color | _opt_toboolean),
       colors:          (.colors | _opt_tostring),
       compact:         (.compact | _opt_toboolean),
-      decode_file:     (.decode_file | _opt_toarray(type == "string")),
+      decode_file:     (.decode_file | _opt_toarray(_opt_is_string_pair)),
       decode_format:   (.decode_format | _opt_tostring),
       decode_progress: (.decode_progress | _opt_toboolean),
       depth:           (.depth | _opt_tonumber),
       display_bytes:   (.display_bytes | _opt_tonumber),
       expr:            (.expr | _opt_tostring),
       expr_file:       (.expr_file | _opt_tostring),
-      filename:        (.filenames | _opt_toarray(type == "string")),
+      filenames:       (.filenames | _opt_toarray(type == "string")),
       include_path:    (.include_path | _opt_tostring),
       join_string:     (.join_string | _opt_tostring),
       line_bytes:      (.line_bytes | _opt_tonumber),
diff --git a/pkg/interp/testdata/args.fqtest b/pkg/interp/testdata/args.fqtest
index d04459d7e..b073c02c4 100644
--- a/pkg/interp/testdata/args.fqtest
+++ b/pkg/interp/testdata/args.fqtest
@@ -35,9 +35,7 @@ null> ^D
 $ fq -i . /test.mp3
 mp3> ^D
 $ fq -n
-exitcode: 2
-stderr:
-Usage: fq [OPTIONS] [--] [EXPR] [FILE...]
+null
 $ fq -ni
 null> ^D
 $ fq -n 123
diff --git a/pkg/interp/testdata/basic.fqtest b/pkg/interp/testdata/basic.fqtest
index 081a77e9b..f214c3a59 100644
--- a/pkg/interp/testdata/basic.fqtest
+++ b/pkg/interp/testdata/basic.fqtest
@@ -25,7 +25,7 @@ mp3> .headers[0].magic._format
 null
 mp3> ^D
 $ fq -d raw .
-   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.: {} - (raw)
+   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.: {} <stdin> (raw)
 0x0|61 62 63 0a|                                   |abc.|           |  unknown0: raw bits
 stdin:
 abc
diff --git a/pkg/interp/testdata/inputs.fqtest b/pkg/interp/testdata/inputs.fqtest
index 4d5028039..e5e03e3da 100644
--- a/pkg/interp/testdata/inputs.fqtest
+++ b/pkg/interp/testdata/inputs.fqtest
@@ -41,6 +41,10 @@ $ fq -d raw -n '(input,input,input,input) | todescription' /a /b /c
 exitcode: 5
 stderr:
 error: break
+$ fq -d raw input_filename
+"<stdin>"
+stdin:
+test
 $ fq -d raw input_filename /a /b /c
 "/a"
 "/b"
diff --git a/pkg/interp/testdata/options.fqtest b/pkg/interp/testdata/options.fqtest
index fba9b8257..4d688c7cc 100644
--- a/pkg/interp/testdata/options.fqtest
+++ b/pkg/interp/testdata/options.fqtest
@@ -18,7 +18,7 @@ $ fq -n options
   "expr_eval_path": "arg",
   "expr_file": null,
   "filenames": [
-    "-"
+    null
   ],
   "include_path": null,
   "join_string": "\n",
@@ -58,6 +58,8 @@ $ fq -o compact=true -n options.compact
 true
 $ fq -o compact=aaa -n options.compact
 false
+$ fq -n -o 'decode_file=[["a", "/test.mp3"]]' '$a | format'
+"mp3"
 $ fq -o decode_progress=false -n options.decode_progress
 false
 $ fq -o decode_progress=aaa -n options.decode_progress
@@ -70,10 +72,14 @@ $ fq -o display_bytes=10 -n options.display_bytes
 10
 $ fq -o display_bytes=true -n options.display_bytes
 16
+$ fq -n -o expr=123
+123
 $ fq -o expr_file=test.jq -n options.expr_file
 exitcode: 2
 stderr:
 error: open testdata/test.jq: no such file or directory
+$ fq -o 'filenames=["/test.mp3"]' format
+"mp3"
 $ fq -o include_path=path -n options.include_path
 "path"
 $ fq -o 'join_string=aaa\n' -n options.join_string