David Portabella David Portabella - 11 months ago 40
Linux Question

get a part of a binary file using gnu-coreutils, bash

I want to get a part of a binary file, from byte #480161397 to #480170447 (included, 9051 bytes in total)

I use

cut -b
, and I expected the size of trunk1.gz to be 9051 bytes, but I get a different result.

$ wget https://commoncrawl.s3.amazonaws.com/crawl-data/CC-MAIN-2016-07/segments/1454701152097.59/warc/CC-MAIN-20160205193912-00264-ip-10-236-182-209.ec2.internal.warc.gz

$ cut -b480161397-480170447 CC-MAIN-20160205193912-00264-ip-10-236-182-209.ec2.internal.warc.gz >trunk1.gz

$ echo $((480170447-480161397+1))

$ ls -l trunk1.gz
-rw-r--r-- 1 david staff 3400324 Sep 8 10:28 trunk1.gz

What is wrong?

Answer Source

If you work with binary, I advise you to use dd command.

dd if=trunk1.gz bs=1 skip=480161397 count=9051 of=output.bin

bs is the block size and is set to 1 byte.