Powershell string variable with UTF-8 encoding

问题

I checked many related questions about this, but I couldn't find something that solves my problem. Basically, I want to store a UTF-8 encoded string in a variable and then use that string as a file name.

For example, I'm trying to download a YouTube video. If we print the video title, the non-English characters show up (ytd here is youtube-dl):

./ytd https://www.youtube.com/watch?v=GWYndKw_zbw -e

Output: [LEEPLAY] 시티팝 입문 City Pop MIX (Playlist)

But if I store this in a variable and print it, the Korean characters are ignored:

$vtitle= ./ytd https://www.youtube.com/watch?v=GWYndKw_zbw -e

$vtitle

Output:[LEEPLAY] City Pop MIX (Playlist)

回答1:

When PowerShell interprets output from external programs (such as ytd in your case), it assumes that the output uses the character encoding reflected in [Console]::OutputEncoding.

Note:

• Interpreting refers to cases where PowerShell captures (e.g., $output = ...), relays (e.g., ... | Select-String ...), or redirects (e.g., ... > output.txt) the external program's output.

• By contrast, printing directly to the display is not affected, because PowerShell isn't involved (which explains why the characters looked as expected in your console when ytd's output printed directly to it).

If the encoding reported by [Console]::OutputEncoding is not the same encoding used by the external program at hand, PowerShell misinterprets the output.

To fix that, you must (temporarily) set [Console]::OutputEncoding] to match the encoding used by the external program.

For instance, let's assume an executable foo.exe that outputs UTF-8-encoded text:

# Save the current encoding and switch to UTF-8.
$prev = [Console]::OutputEncoding
[Console]::OutputEncoding = [Text.Encoding]::Utf8

# PowerShell now interprets foo's output correctly as UTF-8-encoded.
# and $output will correctly contain CJK characters.
$output = foo https://example.org -e

# Restore the previous encoding.
[Console]::OutputEncoding = $prev

Important:

• Modifying [Console]::OutputEncoding to match an external program's character encoding is broken in PowerShell Core v6.x , but fortunately has been fixed in v7.0+ - see this GitHub bug report; Windows PowerShell is unaffected.

• [Console]::OutputEncoding by default reflects the encoding associated with the legacy system locale's OEM code page, as reported by chcp (e.g. 437 on US-English systems).

  • Recent versions of Windows 10 now allow setting the system locale to code page 65001 (UTF-8) (the feature is still in beta as of Window 10 version 1909), which is great, considering that most modern command-line utilities "speak" UTF-8.

---

With the specific program at hand, youtube-dl, js2010 has discovered that capturing in a variable works without extra effort if you pass --encoding utf-16.

The reason this works is that the resulting UTF16-LE-encoded output is preceded by a BOM (Byte-Order Mark).

(Note that --encoding utf-8 does not work, because youtube-dl then does not emit a BOM.)

Windows PowerShell is capable of detecting and properly decoding UTF-16LE-encoded and UTF-8-encoded text irrespective of the effective [Console]::OutputEncoding] IF AND ONLY IF the output is preceded by a BOM.

Caveats:

• This does not work in PowerShell Core (on any of the supported platforms).

• Even in Windows PowerShell you'll rarely be able to take advantage of this obscure behavior, because using a BOM in stdout output is atypical (it is typically only used in files).

回答2:

This works for me in the ISE. Youtube-dl is from ytdl-org.github.io. Actually the ise wouldn't be needed, but the filename will only show correctly in something like explorer.

# get title
# utf-16 has a bom, or use utf-8-sig, this program is python based
$a = .\youtube-dl -e https://www.youtube.com/watch?v=Qpy7N4oFQUQ --encoding utf-16
$a
Gacharic Spin - 赤裸ライアー教則映像(short ver.)TOMO-ZO編

You might have similar luck in vscode (or osx/linux).

来源：https://stackoverflow.com/questions/58438095/powershell-string-variable-with-utf-8-encoding