How to unzip only the first few lines of a zip archive?

Question

I have a zipped text file a.zip I want to read the first 10 lines of it. Is it possible to do that without unzipping the whole file?

Solution

This simple pipe-script works for me:

zcat a.zip | head -n 10

Here:

• zcat a.zip - unpacks zip-archive and sends its contents to standard output
• | pipes zcat output to head input
• head -n 10 - shows first 10 lines from its standard input

Comments

[yukashima huksay]

this unzips the whole file.

[PerlDuck]

@yukashima I'd guess it depends on the size of a.zip. When head terminates (after printing 10 lines) the zcat (which is gzip -dc behind the scenes) should receive a SIGPIPE and stop unzipping.

[Xen2050]

@yukashimahuksay How do you know it unzips the whole file? I think all zip files keep the file list at the end of the archive, maybe it's just reading the whole file but not actually unzipping it

[user27164]

I can confirm by example that it does not unzip the whole file as intended. zcat verybigfile.zip | head -10 prints the first 10 lines immediately. A full unzip would take ca. 10 minutes.