问题
If I run a command like this:
Write-Output March > a.txt
I get this result:
U+FEFF
M U+004D
a U+0061
r U+0072
c U+0063
h U+0068
U+000D
\n U+000A
I do not want the BOM. I tried different actions, like this:
$OutputEncoding = [System.Text.UTF8Encoding]::new($false)
$PSDefaultParameterValues['*:Encoding'] = 'utf8'
[Console]::InputEncoding = [System.Text.UTF8Encoding]::new($false)
[Console]::OutputEncoding = [System.Text.UTF8Encoding]::new($false)
but none of them seem to address the issue. Note I am using PowerShell 5.1. I did see some similar questions, but not quite the same issue as this, as they were dealing with piping and external commands.
回答1:
tl;dr
If you want Windows PowerShell's
>
operator and cmdlets such asOut-File
to output BOM-less UTF-8, your only option is to change to that encoding system-wide:As a one-time step, run
intl.cpl
to open Control Panel's Region settings, switch to theAdministrative
tab, click theChange system locale...
button and checkBeta: Use Unicode UTF-8 for worldwide language support
.Run the following in every session, which is best done via your
$PROFILE
file:$PSDefaultParameterValues['*:Encoding'] = 'Default'
See the next section for the important ramifications of this change and background information.
Otherwise, you must use .NET APIs directly - see the answers to this question - or write a PowerShell-friendly wrapper around them - see this answer.
Alternatively, you can install the cross-platform PowerShell [Core] v6+ edition, which consistently defaults to BOM-less UTF-8.
On Windows 10, you can make Windows PowerShell default consistently to BOM-less UTF-8 - assuming you're willing to change to this encoding system-wide:
Change your system locale (language for non-Unicode programs) to BOM-less UTF-8, as described in this answer:
In short: Run
intl.cpl
to open Control Panel's Region settings, switch to theAdministrative
tab, click theChange system locale...
button and check theBeta: Use Unicode UTF-8 for worldwide language support
; note that you need administrative privileges to make this change and that a reboot is required to make the change take effect.Caveats:
This change sets both the OEM and the ANSI code page to
65001
, i.e. BOM-less UTF-8, which affects all console windows.As of Windows 10 version 20H2, this feature is still in beta and can break legacy console applications.
Then, in Windows PowerShell v5.1, add the following to your
$PROFILE
file (this isn't necessary in PowerShell [Core] v6+):$PSDefaultParameterValues['*:Encoding'] = 'Default'
$OutputEncoding = [System.Text.Utf8Encoding]::new($false)
With this in effect:
All file-writing[1] Windows PowerShell cmdlets that have an
-Encoding
parameter will then default to BOM-less UTF-8 (Default
represents the active ANSI code page, which will then be65001
, i.e. BOM-less UTF-8) - notably including>
/Out-File
/Set-Content
.Windows PowerShell then also reads BOM-less files as UTF-8, including source code and via Get-Content; normally, Windows PowerShell interprets BOM-less files based on the system locale-appropriate ANSI code page (whereas PowerShell [Core] v6+ assumes UTF-8).
By virtue of the OEM code page then being BOM-less UTF-8 (as reflected in
chcp.com
reporting65001
), PowerShell will also use BOM-less UTF-8:- When interpreting data received from the outside via its CLI.
- When interpreting data received from an external program inside a PowerShell session.
- The
$OutputEncoding
assignment above additionally ensures that PowerShell sends data to external programs as BOM-less UTF-8. (This preference variable fortunately now defaults to BOM-less UTF-8 in PowerShell [Core] v6+.)
Note that the above also makes all PowerShell [Core] v6+ console windows use BOM-less UTF-8 in all respects, except that you don't need the $PROFILE
additions (though they do no harm).
Background information:
> a.txt
is effectively the same as| Out-File a.txt
.Windows PowerShell's
>
/>>
/ Out-File default to UTF-16LE ("Unicode")[2], which invariably uses a BOM.You have two options for choosing a different encoding:
Use
Out-File
explicitly and use its-Encoding
parameter.In v5.1 (and also in PowerShell [Core] v6+), you can set the default encoding for
>
/>>
/Out-File
via the$PSDefaultParameterValues
preference variable, as discussed in this answer.However, in Windows PowerShell, the
utf8
value for-Encoding
is invariably a UTF-8 encoding with BOM, so - unless you're willing to switch to UTF-8 system-wide, as explained above - the only way to create BOM-less UTF-8 files is to use .NET APIs directly.- Note that in PowerShell [Core] v6+ the
utf8
value accepted by an-Encoding
parameter now (more sensibly) refers to a BOM-less UTF-8 encoding; if you do want a UTF-8 BOM there, useutf8BOM
instead.
- Note that in PowerShell [Core] v6+ the
As for what you tried:
The properties and variables you tried are related only to how PowerShell - in both editions - communicates with external programs:
$OutputEncoding
determines the encoding PowerShell uses when sending data via the pipeline to an external program (which the latter can read via stdin (standard input).[Console]::OutputEncoding
determines the encoding that PowerShell uses when interpreting output received from an external program.[Console]::InputEncoding
is the encoding that PowerShell uses when it receives data from the outside, when its CLI is called.- Caveat: You can't change this encoding from within your PowerShell session in this case, as that would be too late.
- It must be set by the caller, before calling the PowerShell CLI, which from
cmd.exe
is most easily done withchcp 65001
(see caveat re callingchcp
from inside PowerShell below). While that invariably sets both[Console]::InputEncoding
and[Console]::OutputEncoding
, that is usually desirable.
Note:
On Windows,
[Console]::OutputEncoding
and[Console]::InputEncoding
by default reflect the encoding of the legacy system locale's OEM code page, as reported bychcp.com
; on Unix-like platforms (PowerShell [Core] v6+), it is (virtually without exception, these days) (BOM-less) UTF-8Due to caching of the encodings in these .NET properties, you cannot use
chcp.com
from inside PowerShell to change these properties - instead, assign the desired encoding directly.See this answer for more information, which discusses how to make console windows on Windows use BOM-less UTF-8 consistently with respect to external programs.
[1] Technically, this preference is also applied to file-reading cmdlets, which is neither strictly necessary for BOM-less files nor does it do any harm for files with a BOM - even if that BOM indicates a UTF-16 or UTF-32 encoding - because a BOM alway overrides an -Encoding
argument.
[2] Unfortunately, in Windows PowerShell the default encodings vary wildly across cmdlets - see the bottom section of this answer.
回答2:
If you're only using ascii characters, set-content would be fine in powershell 5.1:
Write-Output March | set-content a.txt
'March' | set-content a.txt
Or set the default encoding of out-file to ascii in your $profile with this hashtable. The default encoding of out-file is utf16 or 'unicode' encoding. '>' is a shortcut for out-file. The name of the key has to be quoted because it contains a colon. utf8nobom isn't available until later powershell versions. '>>' also invokes out-file and may mix encodings in the same file.
$PSDefaultParameterValues = @{ 'out-file:encoding' = 'ascii' }
Then this will make an ascii file:
Write-Output March > a.txt
来源:https://stackoverflow.com/questions/65191663/write-output-with-no-bom