Question

On a Linux desktop (RHEL4) I want to extract a range of bytes (typically less than 1000) from within a large file (>1 Gig). I know the offset into the file and the size of the chunk.

I can write code to do this but is there a command line solution?

Ideally, something like:

magicprogram --offset 102567 --size 253 < input.binary > output.binary

Answer 1

Try dd:

dd skip=102567 count=253 if=input.binary of=output.binary bs=1

The option bs=1 sets the block size, making dd read and write one byte at a time. The default block size is 512 bytes.

The value of bs also affects the behavior of skip and count since the numbers in skip and count are the numbers of blocks that dd will skip and read/write, respectively.