How can I tail a zipped file without reading its entire contents?
I want to emulate the functionality of gzcat | tail -n.
This would be helpful for times when there are huge files (of a few GB's or so). Can I tail the last few lines of such a file w/o reading it from the beginning? I doubt that this won't be possible since I'd guess for gzip, the encoding would depend on all the previous text.
But still I'd like to hear if anyone has tried doing something similar - maybe investigating over a compression algorithm that could provide such a feature.
Answer
No, you can't. The zipping algorithm works on streams and adapts its internal codings to what the stream contains to achieve its high compression ratio.
Without knowing what the contents of the stream are before a certain point, it's impossible to know how to go about de-compressing from that point on.
Any algorithm which allows you to de-compress arbitrary parts of it will require multiple passes over the data to compress it.