Read *.mat files inside a zip file without extracting(/unzipping) the zip file

Hello Everybody

I have several zip files with large sizes, each of them contains at least 500 mat files and each of these mat files is a large matrix containing numbers, e.g. 8000*2000 double.

I don't have enough free space to extract these zip files and then import the data inside these matrices. So, I want to know is there any possibility to read these matrices without unzipping these zip files?

Thank you in advance

Answer 1

[Mehmed Saad]

https://ch.mathworks.com/matlabcentral/answers/10945-read-files-in-zip-file-without-unzipping#answer_15061

https://ch.mathworks.com/matlabcentral/answers/112027-how-to-read-a-zipped-file-without-unzipping-it

[K1]

Thank you for your reply. Actually, I had seen these threads before, but these solutions did not work for me. Maybe this was my problem that I couldn't use them correctly.

[Mehmed Saad]

1. Suppose i have 1 zip file with 100 mat files (and no other files in it)
2. pass its name to zip_file_name with directory
3. listzipcontents function lists all the filenames in zip file
4. run for loop for all the files i.e. 100 for this case
5. extractFile is a function which extracts a specific file from zip file. it has three inputs, zipfilename,path at which you want the file to extract and the file name which we want to extract
6. after single file extraction in your tmp_folder, load it in matlab using load command, then delete it from the tmp_folder. it will load all files from zip folder but 1 by 1.

clear
zip_file_name = 'your zip file name';
filelist = listzipcontents(zip_file_name);
tmp_folder = 'C:\Users\PROJECT PC\Documents\MATLAB\';
for i=1:length(filelist)
extractFile(zip_file_name,tmp_folder, filelist{i});
load([tmp_folder,filelist{i}])
delete(filelist{i})
end

Source of this function

https://ch.mathworks.com/matlabcentral/fileexchange/32089-listzipcontents

License

Copyright (c) 2011, Bob Hamans All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

function filelist = listzipcontents(zipFilename)
% Create a Java file of the ZIP filename.
zipJavaFile  = java.io.File(zipFilename);
% Create a Java ZipFile and validate it.
zipFile = org.apache.tools.zip.ZipFile(zipJavaFile);
% Extract the entries from the ZipFile.
entries = zipFile.getEntries;
% Initialize the file list.
filelist={};
% Loop through the entries and add to the file list.
while entries.hasMoreElements
    filelist = cat(1,filelist,char(entries.nextElement));
end
end

Source of this function

https://stackoverflow.com/questions/37591790/how-to-extract-a-single-file-from-a-zip-archive-in-matlab

function [] = extractFile(zipFilename, outputDir, outputFile)
% extractFile

% Obtain the entry's output names
outputName = fullfile(outputDir, outputFile);

% Create a stream copier to copy files.
streamCopier = ...
    com.mathworks.mlwidgets.io.InterruptibleStreamCopier.getInterruptibleStreamCopier;

% Create a Java zipFile object and obtain the entries.
try
    % Create a Java file of the Zip filename.
    zipJavaFile = java.io.File(zipFilename);

    % Create a java ZipFile and validate it.
    zipFile = org.apache.tools.zip.ZipFile(zipJavaFile);

    % Get entry
    entry = zipFile.getEntry(outputFile);

catch exception
    if ~isempty(zipFile)
        zipFile.close;
    end
    delete(cleanUpUrl);
    error(message('MATLAB:unzip:unvalidZipFile', zipFilename));
end

% Create the Java File output object using the entry's name.
file = java.io.File(outputName);

% If the parent directory of the entry name does not exist, then create it.
parentDir = char(file.getParent.toString);
if ~exist(parentDir, 'dir')
    mkdir(parentDir)
end

% Create an output stream
try
    fileOutputStream = java.io.FileOutputStream(file);
catch exception
    overwriteExistingFile = file.isFile && ~file.canWrite;
    if overwriteExistingFile
        warning(message('MATLAB:extractArchive:UnableToOverwrite', outputName));
    else
        warning(message('MATLAB:extractArchive:UnableToCreate', outputName));
    end
    return
end

% Create an input stream from the API
fileInputStream = zipFile.getInputStream(entry);

% Extract the entry via the output stream.
streamCopier.copyStream(fileInputStream, fileOutputStream);

% Close the output stream.
fileOutputStream.close;
end

[K1]

I really appreciate your detailed explanation.

[Stephen23]

@Mehmed Saad: the license of listzipcontents states that you need to include the license when you dstribute it. I don't see any license on this page.

[Mehmed Saad]

sorry sir. see the updated comment.

It is better to provide just the source instead of posting their code. got it

[Darcy Cordell]

Does this only work on Windows? And does it only work if the zip file has the *.zip extension? I have zipped fies on a Mac with *.gz extension. Any help is appreciated.