MySQL command‑line client shows garbled Unicode characters in error messages and help output

Answer

Specifying --default-character-set=utf8mb4 alone does **not** guarantee correct Unicode echo or error‑message display. It only sets the client‑side character set for the initial handshake; the server may still return results in its own charset (latin1) unless the session variables are overridden after connection.

Confirmed facts

• The MySQL 8.0 client honors --default-character-set for the handshake, which sets character_set_client, character_set_connection and character_set_results to the given value.
• If the server’s default character set differs, it will send results in that charset unless the session variables are changed with SET NAMES (or individual SET character_set_* statements).
• Error messages, help text, and echoed input are produced using character_set_results; therefore they will appear garbled if that variable remains latin1 while the terminal expects UTF‑8.
• When using the pager command with an external program such as less, the client’s character_set_results must match the terminal’s encoding, and the pager’s LESSCHARSET should be left unset or explicitly set to utf-8 to avoid double re‑encoding.
• A UTF‑8 capable terminal (e.g., LANG=en_US.UTF-8) is required; otherwise even correct MySQL settings will show replacement symbols.

Steps to obtain proper Unicode display

1. Start the client with UTF‑8 forced at handshake:

   mysql --default-character-set=utf8mb4 -u your_user -p

2. Immediately after connecting, set the session to UTF‑8:

   SET NAMES utf8mb4;

   (Equivalent: SET character_set_client=utf8mb4, character_set_results=utf8mb4, character_set_connection=utf8mb4;)
3. Verify the session variables:

   STATUS;

   Look for Character set: utf8mb4 under Server characterset and Client characterset.
4. Test Unicode input and output:

   INSERT INTO test (col) VALUES ('😀','é','中');

   SELECT * FROM test;

   The characters should appear correctly in the terminal.
5. If you use a pager, enable it and ensure charset alignment:

   pager less -R

   Then run a query that returns Unicode data; less should display the characters without replacement symbols. If you see mojibake, check:
   • echo $LANG – should end with .UTF-8 or .utf8.
   • echo $LESSCHARSET – ideally unset or set to utf-8.
6. To isolate pager effects, toggle it off and on:

   nopager

   Verify Unicode works, then re‑enable the pager and compare.

When the recommendation changes

If the terminal locale is not UTF‑8 (e.g., LANG=C), then even correct MySQL settings will show garbled output. In that case you must adjust the terminal’s locale or launch the terminal in a UTF‑8 locale before proceeding.