When entering "set" in the command line of Mac OS X, the output shows LANG=zh_CN.UTF-8. However, when using putty or SecureCRT to operate via SSH, Chinese characters are displayed as "?".
Solution: After logging in, enter
LANG=zh_CN.UTF-8
export LANG
to resolve the issue.
Alternatively, you can add the following to ~/.bash_profile
LANG=zh_CN.UTF-8
export LANG