merge csv files

Merge CSV files or TXT files in a folder – using Excel or CMD

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Often we face the challenge of having to merge csv files or txt files in a folder, into a single file. Excel is the obvious tool for such tasks and today I will show a couple of easy ways for merging multiple files, in a single or even a whole structure of folders, into a single CSV or text file. To merge csv files or other text files it is often best to use Visual Basic for Applications in Excel.

Let’s start with the simplest approach using Windows Command line without having to use Excel.

Merge CSV files using Windows CMD

This approach uses the Windows Command line Copy command.

Open the folder which should contain your CSV or TXT files

Open in Windows Explorer the folder containing CSV or TXT files to be merged. These should be without headers or only the first file should be with headers.
merge CSV files Windows CMD

Open CMD command line within folder

Click on the filepath of the Windows Explorer window and type cmd and hit ENTER.
merge CSV files Windows CMD

Merge the files using COPY command

The CMD Windows command line Window should open. Type the following command and hit ENTER to merge files

copy *.csv merge.csv

merge CSV files Windows CMD
The result will be the newly created merge.csv file with merged data across all CSV files within the directory.

Simply replace *.csv with *.txt to merge text files instead of CSV files

Merge list of csv, txt files

The previous method was very simple and didn’t require the use of Excel or MS Office. The below and the following approaches will provided you with more flexibility when merging files. If you don’t know how to use Macros in Excel read my Tutorial first.

Assuming you want to merge a list of files in a String Array you can use the procedure below. It will merge all provided csv or text files into a single new text file.

Sub MergeFiles(fileNames() As String, newFileName As String, Optional headers As Boolean = True, Optional addNewLine As Boolean = False)
    Dim fileName As Variant, textData As String, fileNo As Integer, result As String, firstHeader As Boolean
    firstHeader = True
    For Each fileName In fileNames
        fileNo = FreeFile
        Open fileName For Input As #fileNo
        textData = Input$(LOF(fileNo), fileNo)
        Close #fileNo
        If headers Then
            result = result & IIf(addNewLine, vbNewLine, "") & IIf(firstHeader, textData, Right(textData, Len(textData) - InStr(textData, vbNewLine)))
            firstHeader = False
        Else
            result = result & IIf(addNewLine, vbNewLine, "") & textData
        End If
    Next fileName
    fileNo = FreeFile
    Open newFileName For Output As #fileNo
    Print #fileNo, result
    Close #fileNo
End Sub

Merge csv, txt files example

See an example below of how to use the MergeFiles procedure:

Dim fileNames(0 To 1) As String
fileNames(0) = "C:\somefolder\test.csv"
fileNames(1) = "C:\somefolder\test1.csv"
    
MergeFiles fileNames, "C:\Merged.csv", True, False

MergeFiles Parameters

fileNames()
Array of Strings representing full file paths to files that are to be merged

newFileName
The name of the new merged file that is to be created

headers
Optional. True by default. This is meant for CSV TXT files (HDR). If True assumes that all files have headers (first row with columns). Only first header will be merged into the new file (newFileName)

addNewLine
Optional. False by default. If True a new line (vbNewLine) character will be added between each merged file

Merge csv, txt files within specified folder

Another case is when you want to merge all csv files within a single folder. This procedure is similar to the previous one with the exception that it runs through all files within a single directory (excluding subdirectories – for that scroll to next procedure). You can also use wildcards such as “*.csv” to be sure that only csv files are merged a not other files – read my post on the VBA Dir function to learn more.

Sub MergeFilesInFolder(folderName As String, newFileName As String, Optional headers As Boolean = True, Optional addNewLine As Boolean = False)
    Dim fileName As Variant, textData As String, fileNo As Integer, result As String, firstHeader As Boolean
    firstHeader = True
    fileName = Dir(folderName)
    Do Until fileName = ""
        fileNo = FreeFile
        Open (Left(folderName, InStrRev(folderName, "\")) & fileName) For Input As #fileNo
        textData = Input$(LOF(fileNo), fileNo)
        Close #fileNo
        If headers Then
            result = result & IIf(addNewLine, vbNewLine, "") & IIf(firstHeader, textData, Right(textData, Len(textData) - InStr(textData, vbNewLine)))
            firstHeader = False
        Else
            result = result & IIf(addNewLine, vbNewLine, "") & textData
        End If
        fileName = Dir
    Loop
    fileNo = FreeFile
    Open newFileName For Output As #fileNo
    Print #fileNo, result
    Close #fileNo
End Sub

Merge csv, txt files in folder example

See an example below of how to use the MergeFilesInFolder procedure:

MergeFilesInFolder "C:\somefolder\*.csv", "C:\MergedFolder.csv", True, False

MergeFilesInFolder Parameters

folderName
A folder including all files to be merged. Wildcards are permitted if supported by the VBA Dir function

newFileName
The name of the new merged file that is to be created

headers
Optional. True by default. This is meant for csv files (HDR). If True assumes that all files have headers (first row with columns). Only first header will be merged into the new file (newFileName)

addNewLine
Optional. False by default. If True a new line (vbNewLine) character will be added between each merged file

Merge csv, txt files within all subfolders

The most complex case is when you want to merge files not only within a certain directory but also within all subdirectories. This will equally work for a scenario when there are no subfolders.

Sub MergeFilesInSubFolders(folderName As String, pattern As String, newFileName As String, Optional headers As Boolean = True, Optional addNewLine As Boolean = False)
    Dim fileName As Variant, folder As Variant, textData As String, fileNo As Integer, result As String, firstHeader As Boolean
    firstHeader = True
    Dim col As Collection
    Set col = New Collection
    col.Add folderName
    TraversePath folderName, col
    For Each folder In col
        fileName = Dir(folder & pattern)
        Do Until fileName = ""
            fileNo = FreeFile
            Open (Left(folder, InStrRev(folder, "\")) & fileName) For Input As #fileNo
            textData = Input$(LOF(fileNo), fileNo)
            Close #fileNo
            If headers Then
                result = result & IIf(addNewLine, vbNewLine, "") & IIf(firstHeader, textData, Right(textData, Len(textData) - InStr(textData, vbNewLine)))
                firstHeader = False
            Else
                result = result & IIf(addNewLine, vbNewLine, "") & textData
            End If
            fileName = Dir
        Loop
    Next folder
    fileNo = FreeFile
    Open newFileName For Output As #fileNo
    Print #fileNo, result
    Close #fileNo
End Sub

Function TraversePath(path As Variant, allDirCollection As Collection)
    Dim currentPath As String, directory As Variant
    Dim dirCollection As Collection
    Set dirCollection = New Collection
     
    currentPath = Dir(path, vbDirectory)
    'Explore current directory
    Do Until currentPath = vbNullString
        If Left(currentPath, 1) <> "." And Left(currentPath, 2) <> ".." And _
            (GetAttr(path & currentPath) And vbDirectory) = vbDirectory Then
            dirCollection.Add path & currentPath & "\"
            allDirCollection.Add path & currentPath & "\"
        End If
        currentPath = Dir()
    Loop
     
    'Explore subsequent directories
    For Each directory In dirCollection
        TraversePath directory, allDirCollection
    Next directory
End Function
Read this post to learn more on using the VBA Dir function to traverse directories and subdirectories

Merge csv, txt files within subfolders example

See an example below of how to use the MergeFilesInSubFoldersprocedure:

MergeFilesInSubFolders "C:\somefolder\", "C:\MergedSubFolders.csv", True, False

MergeFilesInSubFolders Parameters

folderName
A folder with or without subfolders including all files to be merged. Use wildcards with pattern parameter

pattern
If needed a pattern using wildcards permitted by the VBA Dir function

newFileName
The name of the new merged file that is to be created

headers
Optional. True by default. This is meant for csv files (HDR). If True assumes that all files have headers (first row with columns). Only first header will be merged into the new file (newFileName)

addNewLine
Optional. False by default. If True a new line (vbNewLine) character will be added between each merged file

Merge CSV files – filter records

Sometimes we want to download just a subset of records in our CSV files. One way is uploading the data and then filtering it in Excel. But why not do it in one go? See my SQL AddIn or my read CSV file using SQL example in this post here.

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