Unzipping a .Gz File Using C#

Unzip .gz file using c#

The following example from MSDN shows how to use the GZipStream class to compress and decompress a directory of files.

namespace zip
{
    public class Program
    {
        public static void Main()
        {
            string directoryPath = @"c:\users\public\reports";

            DirectoryInfo directorySelected = new DirectoryInfo(directoryPath);

            foreach (FileInfo fileToCompress in directorySelected.GetFiles())
            {
                Compress(fileToCompress);
            }

            foreach (FileInfo fileToDecompress in directorySelected.GetFiles("*.gz"))
            {
                Decompress(fileToDecompress);
            }
        }

        public static void Compress(FileInfo fileToCompress)
        {
            using (FileStream originalFileStream = fileToCompress.OpenRead())
            {
                if ((File.GetAttributes(fileToCompress.FullName) & FileAttributes.Hidden) != FileAttributes.Hidden & fileToCompress.Extension != ".gz")
                {
                    using (FileStream compressedFileStream = File.Create(fileToCompress.FullName + ".gz"))
                    {
                        using (GZipStream compressionStream = new GZipStream(compressedFileStream, CompressionMode.Compress))
                        {
                            originalFileStream.CopyTo(compressionStream);
                            Console.WriteLine("Compressed {0} from {1} to {2} bytes.",
                                fileToCompress.Name, fileToCompress.Length.ToString(), compressedFileStream.Length.ToString());
                        }
                    }
                }
            }
        }

        public static void Decompress(FileInfo fileToDecompress)
        {
            using (FileStream originalFileStream = fileToDecompress.OpenRead())
            {
                string currentFileName = fileToDecompress.FullName;
                string newFileName = currentFileName.Remove(currentFileName.Length - fileToDecompress.Extension.Length);

                using (FileStream decompressedFileStream = File.Create(newFileName))
                {
                    using (GZipStream decompressionStream = new GZipStream(originalFileStream, CompressionMode.Decompress))
                    {
                        decompressionStream.CopyTo(decompressedFileStream);
                        Console.WriteLine("Decompressed: {0}", fileToDecompress.Name);
                    }
                }
            }
        }
    }
}

Unzipping a .gz file using C#

I've used .Net's built-in GZipStream for gzipping byte streams and it works just fine. I suspect that your files are tarred first, before being gzipped.

You've asked for code, so here's a sample, assuming you have a single file that is zipped:

FileStream stream = new FileStream("output.xml", FileMode.Create); // this is the output
GZipStream uncompressed = new GZipStream(stream, CompressionMode.Decompress);

uncompressed.Write(bytes,0,bytes.Length); // write all compressed bytes
uncompressed.Flush();
uncompressed.Close();

stream.Dispose();

Edit:

You've changed your question so that the file is a tar.gz file - technically my answer is not applicable to your situation, but I'll leave it here for folks who want to handle .gz files.

How do you unzip a gz file in memory using GZipStream?

If you are inserting data into the stream, make sure to seek back to its origin before un-gzipping it.

The following should fix your troubles:

            using (var fileStream = new MemoryStream())
            {
                client.DownloadFile(file.FullName, fileStream); // Success! All is good here, so far. :)
                fileStream.Seek(0, SeekOrigin.Begin);

                using (var gzStream = new GZipStream(fileStream, CompressionMode.Decompress))
                {
                    using (var outputStream = new MemoryStream())
                    {
                        gzStream.CopyTo(outputStream);
                        byte[] outputBytes = outputStream.ToArray(); // No data. Sad panda. :'(
                        ftpFile.FileContents = Encoding.ASCII.GetString(outputBytes);
                        fileResults.Add(ftpFile);
                    }
                }
            }

How do you download and extract a gzipped file with C#?

To compress:

using (FileStream fStream = new FileStream(@"C:\test.docx.gzip", 
FileMode.Create, FileAccess.Write)) {
    using (GZipStream zipStream = new GZipStream(fStream, 
    CompressionMode.Compress)) {
        byte[] inputfile = File.ReadAllBytes(@"c:\test.docx");
        zipStream.Write(inputfile, 0, inputfile.Length);
    }
}

To Decompress:

using (FileStream fInStream = new FileStream(@"c:\test.docx.gz", 
FileMode.Open, FileAccess.Read)) {
    using (GZipStream zipStream = new GZipStream(fInStream, CompressionMode.Decompress)) {   
        using (FileStream fOutStream = new FileStream(@"c:\test1.docx", 
        FileMode.Create, FileAccess.Write)) {
            byte[] tempBytes = new byte[4096];
            int i;
            while ((i = zipStream.Read(tempBytes, 0, tempBytes.Length)) != 0) {
                fOutStream.Write(tempBytes, 0, i);
            }
        }
    }
}

Taken from a post I wrote last year that shows how to decompress a gzip file using C# and the built-in GZipStream class.
http://blogs.msdn.com/miah/archive/2007/09/05/zipping-files.aspx

As for downloading it, you can use the standard WebRequest or WebClient classes in .NET.

C# Decompress .GZip to file

Opening the FileStream with the FileMode.Create will overwrite the existing file as documented here. This will cause the file to be empty when you try to decompress it, which in turn leads to an empty output-file.

Below is a working code sample, note that it is async, this can be changed by leaving out async/await and changing the call to the regular CopyTo-method and changing the return type to void.

public static async Task DecompressGZip(string inputPath, string outputPath)
{
    using (var input = File.OpenRead(inputPath))
    using (var output = File.OpenWrite(outputPath))
    using (var gz = new GZipStream(input, CompressionMode.Decompress))
    {
        await gz.CopyToAsync(output);
    }
}

Unzipping a gz file in c# : System.IO.InvalidDataException: 'The archive entry was compressed using an unsupported compression method.'

I am not sure what the issue is but after reading this post

Decompressing using GZipStream returns only the first line

I changed to SharZipLib (http://www.icsharpcode.net/opensource/sharpziplib/) and it worked

decompress a .gz file using GZipStream

You need to decompress but you set CompressionMode.Compress, replace it with CompressionMode.Decompress.

Example here.

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