Added os bang

ucl/builtins/os_test.go

@@ -60,3 +60,27 @@ func TestOS_Exec(t *testing.T) {
 		})
 	}
 }
+
+func TestOS_Bang(t *testing.T) {
+	tests := []struct {
+		descr string
+		eval  string
+		want  any
+	}{
+		{descr: "run command 1", eval: `os:! "echo 'hello, world'"`, want: "hello, world\n"},
+		{descr: "run command 2", eval: `os:! "date +%Y%m%d"`, want: time.Now().Format("20060102") + "\n"},
+		{descr: "run command 3", eval: `os:! "tr [a-z] [A-Z]" "hello"`, want: "HELLO"},
+		{descr: "run command 4", eval: `os:! "tr -d e" "hello"`, want: "hllo"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.descr, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.OS()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, res)
+		})
+	}
+}