Can't extract a file from a multi-part zip archive using command-line tools.

Question

Can't extract a file from a multi-part zip archive using command-line tools.

I need to split a video file into <500MB chunks for uploading to a site with size restrictions. Using /usr/bin/zip I appear to be able to successfully create a split zip archive, but when I attempt to confirm the files are usable by recombining and then extracting I don't get a usable file. Here are the steps I'm taking to create the split archive:

1. Create zip archive of the video file without applying further compression: /usr/bin/zip -n .mov movie_archive.zip movie_file.mov
2. Split the archive into <500MB chunks: /usr/bin/zip movie_archive.zip --out movie_pieces.zip -s 470m

The result is 12 sub-500MB files (movie_pieces.zip, movie_pieces.z01, movie_pieces.z02, etc.) I then attempt to verify the results:

1. Merge the split archive back into a single file: /usr/bin/zip -s 0 movie_pieces.zip --out merged_pieces.zip
2. Extract the file from the merged archive: /usr/bin/unzip merged_pieces.zip

The second step results in a "bad CRC 68c9a443. (should be af5f6029)" message and an unusable file. Looking at the merged archive and extracted file, which should both be the size of the original movie file, I find they're much smaller—exactly twice the size of a segment of the split archive. This suggests that when merging only two out of the twelve pieces of the split archive are being concatenated. I re-ran the merge command, this time with the -v flag, and got the message:

"zip warning: needs unzip 4.5 on system type 0: movie_file.mov"

Executing "/usr/bin/unzip -v" tells me I'm running unzip version 6.00.

I've run a few additional tests and found that if I try this with considerably smaller movie files the merge works correctly, but for larger ones like the video file I need to send (3.5GB) they don't reassemble correctly.

Any ideas on things I can try? I run into the same problem on both Intel Core i9 and M2 Pro Macs running the most recent version of macOS Sequoia.

Posted on Feb 12, 2026 12:32 PM

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Answer 1

Top-ranking reply

VikingOSX

Level 10

123,722 points

Feb 13, 2026 8:31 AM in response to Andre Molyneux

When you use the following syntax on a 2 GB MP4 Movie (e.g. Ice Cold in Alex (1958):

zip -s 200 master.zip foo.mp4

it generates master.zip and 9 master.z01 .. z09 zip parts of approximately 209 MB each. However, unzip cannot handle that master.zip directly when formed with zip -s, so one must use the following which joins the zip parts into a joined-master.zip:

zip --fix master.zip --out joined-master.zip
zipinfo -1 joined-master.zip
unzip -d temp joined-master.zip

The playable movie is now in the temp folder.

Tested: Tahoe 26.3

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Answer 2

Feb 12, 2026 3:05 PM in response to Rudegar

Thanks for the suggestion! Using iZip, I was able to successfully extract the movie file from the split archive created by the command line version of zip. So that's accomplished my goal (confirming the split archive is usable). It also tells us the problem is with the command line zip utility's ability to put back together a split archive, not a problem with creation.

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Answer 3

Rudegar

Level 10

180,942 points

Feb 12, 2026 1:39 PM in response to Andre Molyneux

if it was me then I would jump ship trying to do it from the terminal and look into various gui zip apps as such seem often to be more full featured.

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Answer 4

Rudegar

Level 10

180,942 points

Feb 13, 2026 1:10 AM in response to Andre Molyneux

suppose you can let them know using their feedback if you wish

Product Feedback - Apple

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