It is possible that, when a large file or set of files needs to be transferred, it may be provided as a compressed file in .zip format and split into multiple files.
The size of these files, as well as the total number of files, will depend on the file size chosen for the splitting.
The files may be presented with different extensions depending on the tool used, but generally, they will be presented as follows: file.zip, file.z01, file.z02, file.z03, etc. Normally the first file (file.zip) is the smallest one, as it is the remaining size that does not occupy the size chosen in the splitting process.
IMPORTANT: The decompression of a zip file in parts requires that all parts are located in the same folder.
In Windows environments, we can use file compression/decompression software such as WinRAR or 7-zip, which can be downloaded free of charge from their official websites.
In both cases, we must take as the file to decompress the root file (the one with no numbering at the end of the extension). In our example, this is split.zip. This will appear with the icon of the compression tool that we have installed and assigned by default to manage .zip files.
On the file with a .zip extension, we click with the right button of the mouse and then: "Open with WinRAR" and we will be able to see the content that composes that .zip. This example shown below, it contains another .zip file without splitting it into multiple files called example.zip.
To decompress it, we can click on the second button "Extract to" and choose the folder where we want to extract it as shown in the following screenshot.
Click the right mouse button on the file with the .zip extension and then we can go to the 7-Zip menu. There we can mainly use the options marked in yellow in the screenshot.
We recommend not to use the option "Extract here" if you do not know the structure of the compressed file, as it could extract all the files in the current directory and mix them with the rest of the files.
In Linux environments we can do this via command terminal with the zip package.
To do this, run it in a terminal:
zip -FF split.zip --out FicheroUnido.zip
Subsequently, you can unzip the resulting FicheroUnido.zip with the unzip command, from the same Linux package. This command would look like this:
If you do not know the directory structure of the .zip file, we recommend that you decompress the file in a directory dedicated to this decompression.
Error checking and debugging
If you encounter errors, make sure you have all the parts that make up the split file in the same directory. Also, make sure that you are trying to unzip the file with a .zip extension and no numbering at the end of the file.
If you still encounter errors decompressing or accessing the contents of these files, here is how to check the integrity with both tools.
Checking with WinRAR
Right-click on the .zip file and then click on "Open with WinRAR".
On the WinRAR screen, click on the third icon "Check", which will check all parts and their integrity.
The expected result will be something like "No errors found during check".
If any file is missing, WinRAR will detect and stop the checking process on the first missing file. That is if we are missing the last two parts, in this first check it will only notify us of the penultimate one.
Checking with 7-Zip
Right-click on the .zip file and then click on "Check file" in the 7-Zip section.
In this check, the message you will receive is "No errors".
If any file is missing, 7-Zip will detect and stop the checking process on the first missing file. That is, if we are missing the last two parts, in this first check it will only notify us of the penultimate one.
In case we have a part of the file, but it is detected as corrupt, we can make a check using the MD5 sum. This is a unique alphanumeric code that must match.
To do this, we need to check the MD5 sum at the nearest point of origin and we need to be sure that the extraction is correct. That is, if we keep the files on the device where we originate the split .zip, we can calculate the MD5 sum there.
On Windows, we have different tools for checking MD5 sums such as WinMD5Free.
On Linux just run the following command:
The result, both on Windows and Linux, on source and destination, should be the same. This verifies that the file is complete and has not changed in size or content.
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