Adding text to a compressed file without uncompressing

[Matt Graham]

> On Oct 31, 2013 1:40 AM, "Bryan O'Neal"
>> So let's say I have a few hundred lines of text I need at the 
>> beginning
>> or end of a big compressed text file. Say a 20GB uncompressed / 4GB
>> compressed JSON or XML doc. Now lets say I have no desire to
>> uncompress this file and I have no desire to use interactive tools
>> like vim. How could I achieve this?

What compression method are you using?  (Storing that much data in one 
XML file seems like a total organizational failure to me, too.)

I don't think you can do this with zip, not sure about lzma, but I 
would guess "not ever at the start of the file for any commonly-used 
compression method".  Data compression's weird like that.

You can do a bit of appending if you're using gzip:

gzip -c file.txt > foo.gz
gzip -c file2.txt >> foo.gz
gzip -dc < foo.gz

(decompresses foo.gz to stdout, you will get file.txt followed by 
file2.txt)

Stephen wrote:
> Tar has a built in append feature so you can add files to the archive

tar will refuse to append things to compressed archives.

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