How to check if zip file is empty in bash

Question

How can I verify if the zip file is empty or not ? I cannot use if -s in bash as the zip file is not always zero in size. if the zip file has empty directories in it, I want to delete the file else extract the file.

Solution 1

If you have the Info-ZIP tools installed (zip, unzip, zipinfo) you can use zipinfo on the zip file and just send the output to /dev/null. The status will be 0 if the file is not empty.

So:

if zipinfo foo.zip > /dev/null; then
    echo not empty
else
    echo empty
fi

Solution 2

If you run zipinfo -t foo.zip the exit status (from $?)will give an error if the zip file has nothing in it. In the version I'm running (3.00) this will be 1 but I imagine that's just a general error code, so the ambiguity might cause you other problems.

You'll also have to deal with the text output of the command which is a string with basic info about the file. I believe this answer is similar to one of those above.

Edit: If you want to avoid the ambiguous return value (and you're in the mood for grep) you could grep the output of the above command for "Empty zipfile".

Comments

[SeanJ]

is it possible with pure bash scripting without even using java jar ?

[Tim Pote]

@nlrreddy See my edits.

[Admin]

this was giving me the same return code but I tweaked the above a little bit. add | grep ^- to look for files and then delete the file if $? is 1. Thank you Laurence

[Tim Pote]

+1 I'd never heard of zipinfo before. @nlrreddy If Laurence solved your issue, feel free to accept his answer by clicking the checkmark on the left.

[JFK]

zipinfo can potentially fail with exit code 1 for other reasons than an empty zip file. If you just look for exit code 1 you are in for trouble.