# sage -c "print diff(x^4,x)"

I'm using 5.3 on Ubuntu 64 bit.

I would like to have the following print **4x^3** to standard out.

```
$ ./sage -c "print diff(x^4,x)"
Traceback (most recent call last):
File "/home/xuwang/sage/local/bin/sage-eval", line 15, in <module>
eval(compile(s,'<cmdline>','exec'))
File "<cmdline>", line 1, in <module>
NameError: name 'x' is not defined
$
```

You can explicitly declare x as a variable: `sage -c "var('x'); print diff(x^4,x)"`

The question remains of why `./sage -c` doesn't behave the same as Sage proper. Sage does have `x` predefined, like it or not.

@kcrisman: see http://trac.sagemath.org/sage_trac/ticket/13598.