Using PowerShell to write a file in UTF-8 without the BOM

Question

Out-File seems to force the BOM when using UTF-8:

$MyFile = Get-Content $MyPath
$MyFile | Out-File -Encoding "UTF8" $MyPath

How can I write a file in UTF-8 with no BOM using PowerShell?

Update 2021

PowerShell has changed a bit since I wrote this question 10 years ago. Check multiple answers below, they have a lot of good information!

Answer 1

Using .NET's UTF8Encoding class and passing $False to the constructor seems to work:

$MyRawString = Get-Content -Raw $MyPath
$Utf8NoBomEncoding = New-Object System.Text.UTF8Encoding $False
[System.IO.File]::WriteAllLines($MyPath, $MyRawString, $Utf8NoBomEncoding)

Answer 2

The proper way as of now is to use a solution recommended by @Roman Kuzmin in comments to @M. Dudley answer:

[IO.File]::WriteAllLines($filename, $content)

(I've also shortened it a bit by stripping unnecessary System namespace clarification - it will be substituted automatically by default.)

Answer 3

I figured this wouldn't be UTF, but I just found a pretty simple solution that seems to work...

Get-Content path/to/file.ext | out-file -encoding ASCII targetFile.ext

For me this results in a utf-8 without bom file regardless of the source format.

Answer 4

Note: This answer applies to Windows PowerShell; by contrast, in the cross-platform PowerShell Core edition (v6+), UTF-8 without BOM is the default encoding, across all cmdlets.

• In other words: If you're using PowerShell [Core] version 6 or higher, you get BOM-less UTF-8 files by default (which you can also explicitly request with -Encoding utf8 / -Encoding utf8NoBOM, whereas you get with-BOM encoding with -utf8BOM).

• If you're running Windows 10 or above and you're willing to switch to BOM-less UTF-8 encoding system-wide - which has far-reaching consequences, however - even Windows PowerShell can be made to use BOM-less UTF-8 consistently - see this answer.

---

To complement M. Dudley's own simple and pragmatic answer (and ForNeVeR's more concise reformulation):

• A simple, (non-streaming) PowerShell-native alternative is to use New-Item, which (curiously) creates BOM-less UTF-8 files by default even in Windows PowerShell:

  # Note the use of -Raw to read the file as a whole.
  # Unlike with Set-Content / Out-File *no* trailing newline is appended.
  $null = New-Item -Force $MyPath -Value (Get-Content -Raw $MyPath)
  

  • Note: To save the output from arbitrary commands in the same format as Out-File would, pipe to Out-String first; e.g.:

     $null = New-Item -Force Out.txt -Value (Get-ChildItem | Out-String) 
    

• For convenience, below is advanced custom function Out-FileUtf8NoBom, a pipeline-based alternative that mimics Out-File, which means:

  • you can use it just like Out-File in a pipeline.
  • input objects that aren't strings are formatted as they would be if you sent them to the console, just like with Out-File.
  • an additional -UseLF switch allows you use Unix-format LF-only newlines ("`n") instead of the Windows-format CRLF newlines ("`r`n") you normally get.

Example:

(Get-Content $MyPath) | Out-FileUtf8NoBom $MyPath # Add -UseLF for Unix newlines

^{Note how (Get-Content $MyPath) is enclosed in (...), which ensures that the entire file is opened, read in full, and closed before sending the result through the pipeline. This is necessary in order to be able to write back to the same file (update it in place).
Generally, though, this technique is not advisable for 2 reasons: (a) the whole file must fit into memory and (b) if the command is interrupted, data will be lost.}

A note on memory use:

• M. Dudley's own answer and the New-Item alternative above require that the entire file contents be built up in memory first, which can be problematic with large input sets.
• The function below does not require this, because it is implemented as a proxy (wrapper) function (for a concise summary of how to define such functions, see this answer).

---

Source code of function Out-FileUtf8NoBom:

Note: The function is also available as an MIT-licensed Gist, and only the latter will be maintained going forward.

You can install it directly with the following command (while I can personally assure you that doing so is safe, you should always check the content of a script before directly executing it this way):

# Download and define the function.
irm https://gist.github.com/mklement0/8689b9b5123a9ba11df7214f82a673be/raw/Out-FileUtf8NoBom.ps1 | iex

function Out-FileUtf8NoBom {

  <#
  .SYNOPSIS
    Outputs to a UTF-8-encoded file *without a BOM* (byte-order mark).

  .DESCRIPTION

    Mimics the most important aspects of Out-File:
      * Input objects are sent to Out-String first.
      * -Append allows you to append to an existing file, -NoClobber prevents
        overwriting of an existing file.
      * -Width allows you to specify the line width for the text representations
        of input objects that aren't strings.
    However, it is not a complete implementation of all Out-File parameters:
      * Only a literal output path is supported, and only as a parameter.
      * -Force is not supported.
      * Conversely, an extra -UseLF switch is supported for using LF-only newlines.

  .NOTES
    The raison d'être for this advanced function is that Windows PowerShell
    lacks the ability to write UTF-8 files without a BOM: using -Encoding UTF8 
    invariably prepends a BOM.

    Copyright (c) 2017, 2022 Michael Klement <mklement0@gmail.com> (http://same2u.net), 
    released under the [MIT license](https://spdx.org/licenses/MIT#licenseText).

  #>

  [CmdletBinding(PositionalBinding=$false)]
  param(
    [Parameter(Mandatory, Position = 0)] [string] $LiteralPath,
    [switch] $Append,
    [switch] $NoClobber,
    [AllowNull()] [int] $Width,
    [switch] $UseLF,
    [Parameter(ValueFromPipeline)] $InputObject
  )

  begin {

    # Convert the input path to a full one, since .NET's working dir. usually
    # differs from PowerShell's.
    $dir = Split-Path -LiteralPath $LiteralPath
    if ($dir) { $dir = Convert-Path -ErrorAction Stop -LiteralPath $dir } else { $dir = $pwd.ProviderPath }
    $LiteralPath = [IO.Path]::Combine($dir, [IO.Path]::GetFileName($LiteralPath))
    
    # If -NoClobber was specified, throw an exception if the target file already
    # exists.
    if ($NoClobber -and (Test-Path $LiteralPath)) {
      Throw [IO.IOException] "The file '$LiteralPath' already exists."
    }
    
    # Create a StreamWriter object.
    # Note that we take advantage of the fact that the StreamWriter class by default:
    # - uses UTF-8 encoding
    # - without a BOM.
    $sw = New-Object System.IO.StreamWriter $LiteralPath, $Append
    
    $htOutStringArgs = @{}
    if ($Width) { $htOutStringArgs += @{ Width = $Width } }

    try { 
      # Create the script block with the command to use in the steppable pipeline.
      $scriptCmd = { 
        & Microsoft.PowerShell.Utility\Out-String -Stream @htOutStringArgs | 
          . { process { if ($UseLF) { $sw.Write(($_ + "`n")) } else { $sw.WriteLine($_) } } }
      }  
      
      $steppablePipeline = $scriptCmd.GetSteppablePipeline($myInvocation.CommandOrigin)
      $steppablePipeline.Begin($PSCmdlet)
    }
    catch { throw }

  }

  process
  {
    $steppablePipeline.Process($_)
  }

  end {
    $steppablePipeline.End()
    $sw.Dispose()
  }

}

Answer 5

Starting from version 6 powershell supports the UTF8NoBOM encoding both for set-content and out-file and even uses this as default encoding.

So in the above example it should simply be like this:

$MyFile | Out-File -Encoding UTF8NoBOM $MyPath

Answer 6

When using Set-Content instead of Out-File, you can specify the encoding Byte, which can be used to write a byte array to a file. This in combination with a custom UTF8 encoding which does not emit the BOM gives the desired result:

# This variable can be reused
$utf8 = New-Object System.Text.UTF8Encoding $false

$MyFile = Get-Content $MyPath -Raw
Set-Content -Value $utf8.GetBytes($MyFile) -Encoding Byte -Path $MyPath

The difference to using [IO.File]::WriteAllLines() or similar is that it should work fine with any type of item and path, not only actual file paths.

Answer 7

This script will convert, to UTF-8 without BOM, all .txt files in DIRECTORY1 and output them to DIRECTORY2

foreach ($i in ls -name DIRECTORY1\*.txt)
{
    $file_content = Get-Content "DIRECTORY1\$i";
    [System.IO.File]::WriteAllLines("DIRECTORY2\$i", $file_content);
}

Answer 8

important!: this only works if an extra space or newline at the start is no problem for your use case of the file
(e.g. if it is an SQL file, Java file or human readable text file)

one could use a combination of creating an empty (non-UTF8 or ASCII (UTF8-compatible)) file and appending to it (replace $str with gc $src if the source is a file):

" "    |  out-file  -encoding ASCII  -noNewline  $dest
$str  |  out-file  -encoding UTF8   -append     $dest

as one-liner

replace $dest and $str according to your use case:

$_ofdst = $dest ; " " | out-file -encoding ASCII -noNewline $_ofdst ; $src | out-file -encoding UTF8 -append $_ofdst

as simple function

function Out-File-UTF8-noBOM { param( $str, $dest )
  " "    |  out-file  -encoding ASCII  -noNewline  $dest
  $str  |  out-file  -encoding UTF8   -append     $dest
}

using it with a source file:

Out-File-UTF8-noBOM  (gc $src),  $dest

using it with a string:

Out-File-UTF8-noBOM  $str,  $dest

• optionally: continue appending with Out-File:

  "more foo bar"  |  Out-File -encoding UTF8 -append  $dest
  

Answer 9

Old question, new answer:

While the "old" powershell writes a BOM, the new platform-agnostic variant does behave differently: The default is "no BOM" and it can be configured via switch:

-Encoding

Specifies the type of encoding for the target file. The default value is utf8NoBOM.

The acceptable values for this parameter are as follows:

• ascii: Uses the encoding for the ASCII (7-bit) character set.
• bigendianunicode: Encodes in UTF-16 format using the big-endian byte order.
• oem: Uses the default encoding for MS-DOS and console programs.
• unicode: Encodes in UTF-16 format using the little-endian byte order.
• utf7: Encodes in UTF-7 format.
• utf8: Encodes in UTF-8 format.
• utf8BOM: Encodes in UTF-8 format with Byte Order Mark (BOM)
• utf8NoBOM: Encodes in UTF-8 format without Byte Order Mark (BOM)
• utf32: Encodes in UTF-32 format.

Source: https://learn.microsoft.com/de-de/powershell/module/Microsoft.PowerShell.Utility/Out-File?view=powershell-7 Emphasis mine

Answer 10

For PowerShell 5.1, enable this setting:

Control Panel, Region, Administrative, Change system locale, Use Unicode UTF-8 for worldwide language support

Then enter this into PowerShell:

$PSDefaultParameterValues['*:Encoding'] = 'Default'

Alternatively, you can upgrade to PowerShell 6 or higher.

https://github.com/PowerShell/PowerShell

Answer 11

I would say to use just the Set-Content command, nothing else needed.

The powershell version in my system is :-

PS C:\Users\XXXXX> $PSVersionTable.PSVersion | fl


Major         : 5
Minor         : 1
Build         : 19041
Revision      : 1682
MajorRevision : 0
MinorRevision : 1682

PS C:\Users\XXXXX>

So you would need something like following.

PS C:\Users\XXXXX> Get-Content .\Downloads\finddate.txt
Thursday, June 23, 2022 5:57:59 PM
PS C:\Users\XXXXX> Get-Content .\Downloads\finddate.txt | Set-Content .\Downloads\anotherfile.txt
PS C:\Users\XXXXX> Get-Content .\Downloads\anotherfile.txt
Thursday, June 23, 2022 5:57:59 PM
PS C:\Users\XXXXX>

Now when we check the file as per the screenshot it is utf8. anotherfile.txt

PS: To answer on the comment query on foreign character issue. The contents from file "testfgnchar.txt" which having the foreign characters, was copied to "findfnchar2.txt" using the following command.

PS C:\Users\XXXXX> Get-Content .\testfgnchar.txt | Set-Content findfnchar2.txt
PS C:\Users\XXXXX>

screen-shot is here.

Note: Currently, there are newer versions of PowerShell exists, than the one I used during answer.

Answer 12

Change multiple files by extension to UTF-8 without BOM:

$Utf8NoBomEncoding = New-Object System.Text.UTF8Encoding($False)
foreach($i in ls -recurse -filter "*.java") {
    $MyFile = Get-Content $i.fullname 
    [System.IO.File]::WriteAllLines($i.fullname, $MyFile, $Utf8NoBomEncoding)
}

Answer 13

    [System.IO.FileInfo] $file = Get-Item -Path $FilePath 
    $sequenceBOM = New-Object System.Byte[] 3 
    $reader = $file.OpenRead() 
    $bytesRead = $reader.Read($sequenceBOM, 0, 3) 
    $reader.Dispose() 
    #A UTF-8+BOM string will start with the three following bytes. Hex: 0xEF0xBB0xBF, Decimal: 239 187 191 
    if ($bytesRead -eq 3 -and $sequenceBOM[0] -eq 239 -and $sequenceBOM[1] -eq 187 -and $sequenceBOM[2] -eq 191) 
    { 
        $utf8NoBomEncoding = New-Object System.Text.UTF8Encoding($False) 
        [System.IO.File]::WriteAllLines($FilePath, (Get-Content $FilePath), $utf8NoBomEncoding) 
        Write-Host "Remove UTF-8 BOM successfully" 
    } 
    Else 
    { 
        Write-Warning "Not UTF-8 BOM file" 
    }  

Source How to remove UTF8 Byte Order Mark (BOM) from a file using PowerShell

Answer 14

If you want to use [System.IO.File]::WriteAllLines(), you should cast second parameter to String[] (if the type of $MyFile is Object[]), and also specify absolute path with $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($MyPath), like:

$Utf8NoBomEncoding = New-Object System.Text.UTF8Encoding $False
Get-ChildItem | ConvertTo-Csv | Set-Variable MyFile
[System.IO.File]::WriteAllLines($ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($MyPath), [String[]]$MyFile, $Utf8NoBomEncoding)

If you want to use [System.IO.File]::WriteAllText(), sometimes you should pipe the second parameter into | Out-String | to add CRLFs to the end of each line explictly (Especially when you use them with ConvertTo-Csv):

$Utf8NoBomEncoding = New-Object System.Text.UTF8Encoding $False
Get-ChildItem | ConvertTo-Csv | Out-String | Set-Variable tmp
[System.IO.File]::WriteAllText("/absolute/path/to/foobar.csv", $tmp, $Utf8NoBomEncoding)

Or you can use [Text.Encoding]::UTF8.GetBytes() with Set-Content -Encoding Byte:

$Utf8NoBomEncoding = New-Object System.Text.UTF8Encoding $False
Get-ChildItem | ConvertTo-Csv | Out-String | % { [Text.Encoding]::UTF8.GetBytes($_) } | Set-Content -Encoding Byte -Path "/absolute/path/to/foobar.csv"

see: How to write result of ConvertTo-Csv to a file in UTF-8 without BOM

Answer 15

One technique I utilize is to redirect output to an ASCII file using the Out-File cmdlet.

For example, I often run SQL scripts that create another SQL script to execute in Oracle. With simple redirection (">"), the output will be in UTF-16 which is not recognized by SQLPlus. To work around this:

sqlplus -s / as sysdba "@create_sql_script.sql" |
Out-File -FilePath new_script.sql -Encoding ASCII -Force

The generated script can then be executed via another SQLPlus session without any Unicode worries:

sqlplus / as sysdba "@new_script.sql" |
tee new_script.log

Update: As others have pointed out, this will drop non-ASCII characters. Since the user asked for a way to "force" conversion, I assume they do not care about that as perhaps their data does not contain such data.

If you care about the preservation of non-ASCII characters, this is not the answer for you.

Answer 16

I have the same error in the PowerShell and used this isolation and fixed it

$PSDefaultParameterValues['*:Encoding'] = 'utf8'

Answer 17

Used this method to edit a UTF8-NoBOM file and generated a file with correct encoding-

$fileD = "file.xml"
(Get-Content $fileD) | ForEach-Object { $_ -replace 'replace text',"new text" } | out-file "file.xml" -encoding ASCII

I was skeptical at this method at first, but it surprised me and worked!

Tested with powershell version 5.1

Answer 18

Could use below to get UTF8 without BOM

$MyFile | Out-File -Encoding ASCII

Answer 19

This one works for me (use "Default" instead of "UTF8"):

$MyFile = Get-Content $MyPath
$MyFile | Out-File -Encoding "Default" $MyPath

The result is ASCII without BOM.