head works too:
head -c 100 file # returns the first 100 bytes in the file
..will extract the first 100 bytes and return them.
What’s nice about using head for this is that the syntax for tail matches:
tail -c 100 file # returns the last 100 bytes in the file
You can combine these to get ranges of bytes. For example, to get the second 100 bytes from a file, read the first 200 with head and use tail to get the last 100:
head -c 200 file | tail -c 100