When working with a double-byte character set, you must use single-byte characters in these situations:

• Single-byte characters for file names. DBCS characters in file names are treated as SBCS characters.
• Single-byte characters for command-line options
• Single-byte characters for command-line arguments
• Single-byte characters for delimiters, such as a slash, braces, parentheses, and so on
• For user-defined environment variables, only SBCS for the names, and SBCS or DBCS for the values
• For the shell environment variables, only IFS, PS1, and PS2 support DBCS values
• For user IDs, passwords, and password phrases
• For device, group, and terminal names.