How can I split a binary file into chunks with certain size with batch script without external software?

Question

There are many reasons to want to split file into chunks - mainly for network transfer (e.g. e-mail attachments) but I\'m sure there are scenarios that could require such t

Answer 1

The example below will split a file, producing multiple output files all smaller than the maxChunkSize supplied. To reassemble, you can use copy /b.

SplitFile.cs
(compile with c:\Windows\Microsoft.NET\Framework\v2.0.50727\csc /out:splitFile.exe SplitFile.cs)

using System;
using System.IO;

namespace SplitFile
{
    class Program
    {
        static void Main(string[] args)
        {
            long maxChunkSize;
            if (args.Length != 3 || !long.TryParse(args[2], out maxChunkSize) || maxChunkSize <= 81920)
            {
                Console.WriteLine("Usage: splitfile.exe inputFile outputprefix maxchunksize");
                Console.WriteLine(" inputfile:     File to split");
                Console.WriteLine(" outputprefix:  Prefix to use for the output name");
                Console.WriteLine("                Ex: out -> { out0001.bin, out0002.bin }");
                Console.WriteLine(" maxchunksize:  Maximum number of bytes in each file");
                Console.WriteLine("                Note: this is the maximum size, not an exact size");
                Console.WriteLine("                Note: chunk size cannot be smaller than 81920 bytes");
                return;
            }

            string inputFilePath = args[0];
            string outputFilePathFormat = string.Format("{0}{{0:0000}}.bin", args[1]);

            using (Stream fsInput = File.Open(inputFilePath, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                byte[] buffer = new byte[81920 /* default from System.Stream */];
                int cOutFileNo = 0;
                Stream destination = getOutputFile(ref cOutFileNo, outputFilePathFormat);
                try
                {
                    int read;
                    while ((read = fsInput.Read(buffer, 0, buffer.Length)) != 0)
                    {
                        if (destination.Length + read > maxChunkSize)
                        {
                            destination.Dispose();
                            destination = getOutputFile(ref cOutFileNo, outputFilePathFormat);
                        }

                        destination.Write(buffer, 0, read);
                    }
                }
                finally
                {
                    destination.Dispose();
                }
            }
        }

        private static Stream getOutputFile(ref int cOutFileNo, string outFileFormat)
        {
            string filename = string.Format(outFileFormat, cOutFileNo);
            cOutFileNo++;

            return File.Open(filename, FileMode.CreateNew, FileAccess.Write, FileShare.None);
        }
    }
}

Example Use:

C:\drop>splitFile.exe ubuntu-rescue-remix-12-04.iso Ubuntu_Split_ 10485760
C:\drop>dir
01/29/2015  17:21       244,570,112 ubuntu-rescue-remix-12-04.iso
01/30/2015  15:27        10,485,760 Ubuntu_Split_0000.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0001.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0002.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0003.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0004.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0005.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0006.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0007.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0008.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0009.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0010.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0011.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0012.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0013.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0014.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0015.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0016.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0017.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0018.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0019.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0020.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0021.bin
01/30/2015  15:27        10,485,760 Ubuntu_Split_0022.bin
01/30/2015  15:27         3,397,632 Ubuntu_Split_0023.bin

C:\drop>copy /b Ubuntu_Split_* Ubuntu_recombined.iso
Ubuntu_Split_0000.bin
Ubuntu_Split_0001.bin
Ubuntu_Split_0002.bin
Ubuntu_Split_0003.bin
Ubuntu_Split_0004.bin
Ubuntu_Split_0005.bin
Ubuntu_Split_0006.bin
Ubuntu_Split_0007.bin
Ubuntu_Split_0008.bin
Ubuntu_Split_0009.bin
Ubuntu_Split_0010.bin
Ubuntu_Split_0011.bin
Ubuntu_Split_0012.bin
Ubuntu_Split_0013.bin
Ubuntu_Split_0014.bin
Ubuntu_Split_0015.bin
Ubuntu_Split_0016.bin
Ubuntu_Split_0017.bin
Ubuntu_Split_0018.bin
Ubuntu_Split_0019.bin
Ubuntu_Split_0020.bin
Ubuntu_Split_0021.bin
Ubuntu_Split_0022.bin
Ubuntu_Split_0023.bin
           1 file(s) copied.

C:\drop>dir Ubuntu*.iso
01/29/2015  17:21       244,570,112 ubuntu-rescue-remix-12-04.iso
01/30/2015  15:27       244,570,112 Ubuntu_recombined.iso

C:\drop>fciv -sha1 ubuntu-rescue-remix-12-04.iso
//
// File Checksum Integrity Verifier version 2.05.
//
02403c37cbdb3e03e00f5176807a793ef63d877c ubuntu-rescue-remix-12-04.iso

C:\drop>fciv -sha1 Ubuntu_recombined.iso
//
// File Checksum Integrity Verifier version 2.05.
//
02403c37cbdb3e03e00f5176807a793ef63d877c ubuntu-rescue-remix-12-04.iso

C:\drop>