Getting and error when I zip files

Hi Matt - to narrow down where the error gets introduced I would recommend the following steps:

1. unzip the file in its original location, i.e. on the original computer where to zipped the file up initially
2. upload the zip file, then download it back to your original computer and unzip it
3. upload the zip file, then download it to your destination computer and unzip it (I guess this is the scenario you described in your original post and therefore I would expect this step to fail)

If unzipping fails at one step then you don't need to do the remaining steps and we have identified where the error occurs.

Cheers
Michael

I have seen somewhere (can't remember where) that ZIP files are limited to 4GB. Not sure whether this refers to the expanded or compressed file size. Does it work for smaller ZIP files? Anyway, I still do't know whether it fails at step 1 or 2.

That means the error is not caused by zipping the file but by transferring it. In other words, whatever you are writing to your FTP server is coming back differently.

Can you open your Terminal app and run the following command on your zip file before and after the transfer?

cksum <your zip file>

This will output 2 large numbers followed the filename.

The large number must be identical for the zip file before and after the transfer. If they are not, then we know the content is being altered.

Since those checksums don't match, the files are not the same. Somewhere in the upload/download process, the file is being corrupted. I don't know a thing about filezilla. Can you try uploading with some other FTP client, such as Cyberduck or Transmit?

That proves without doubt that the file is being corrupted through the transfer as the numbers should be identical before and after the transfer.

Corruption could occur when you transfer the ZIP in ASCII mode. Many FTP program use this mode by default but for transferring ZIP files you must use binary mode.

Cheers
Michael

Does this mean it failed step 1 or 2?

To change the transfer mode in FileZilla, select Transfer >> Transfer Type and choose your option from the list.