I want to break a big file into to smaller files mainly.

I use stream because I do not want to keep the big file in my disk. 

What I am looking it is something similar to:

```
sed -n 'a,bp,' #this uses lines in file while i want bytes

```

or:

```
cat filename|head -c a| tail -c (a-b)  # this way takes too long with big files

```