Grep Japanese characters

[Tak Kunihiro <tkk@misasa.okayama-u.ac.jp>]

I want to grep Japanese string.  I can do it on Emacs for Mac but
cannot do it on Emacs for MS Windows.

I found that I can grep Japanese string using
c:/msys64/usr/bin/grep.exe on command prompt (outside of Emacs).
However, I cannot do it using c:/msys64/usr/bin/grep.exe on command
prompt by M-x shell (inside of Emacs).  I confirm that LC_ALL is set
to en_US.UTF-8 on both environments.

Can you give me a hint to grep Japanese string on Emacs for MS
Windows?



CMD> set
...
LC_ALL=en_US.UTF-8
...

CMD> c:/msys64/usr/bin/cat hello.txt
Hello is こんにちは in Japanese.
Hello is bonjour in French.

CMD> c:/msys64/usr/bin/grep.exe Hello hello.txt
Hello is こんにちは in Japanese.
Hello is bonjour in French.

CMD> c:/msys64/usr/bin/grep.exe "こんにちは" hello.txt
Hello is こんにちは in Japanese.



CMD> c:/emacs-26.1/bin/runemacs -Q
M-x shell

CMD> set
...
LC_ALL=en_US.UTF-8
...

CMD> c:/msys64/usr/bin/grep.exe Hello hello.txt
c:/msys64/usr/bin/grep.exe Hello hello.txt
Hello is こんにちは in Japanese.
Hello is bonjour in French.

CMD> c:/msys64/usr/bin/grep.exe "こんにちは" hello.txt
c:/msys64/usr/bin/grep.exe "こんにちは" hello.txt