What characters should be restricted from a Unix file name?

Question

Consider a Save As dialog with a free text entry where the user enters a file name as free text, then clicks a Save button. The software then validates the file name, and saves the file if the name is valid.

On a Unix file system, what rules should be applied in the validation such that:

• The name will not be difficult to manipulate later in terms of escaping special characters, etc.
• The rules are not so restrictive that saving a file becomes non-user-friendly.

So basically, what is the minimum set of characters that should be restricted from a Unix file name?

Answer 1

The minimum are slash ('/') and NULL ('\0')

Answer 2

Firstly, what you're describing is black listing. Your better option is to white list your characters, as it is easier (from a user perspective) to have characters inserted rather than taken away.

In terms of what would be good in a unix environment:

• a-z
• A-Z
• 0-9
• underscore (_)
• dash (-)
• period (.)

Should cover your basics. Spaces can be okay, but make things difficult. Windows users love them, unix/linux don't. So depending on your target audience choose accordingly.