What characters are forbidden in Windows and Linux directory names?

Windows

The following characters are forbidden in Windows directory (and file) names:

• \ (backslash)
• / (forward slash)
• : (colon)
• * (asterisk)
• ? (question mark)
• " (double quote)
• < (less than sign)
• > (greater than sign)
• | (vertical bar or pipe)

Windows also restricts names that end with a period (.) or space, and it has reserved device names like CON, PRN, AUX, NUL, etc., which cannot be used as valid directory or file names.

Linux/Unix

On Linux/Unix filesystems, practically any character is valid except:

• / (used as the path separator)
• The null character \0

Although these systems allow spaces, punctuation, and special characters, using them can make file management more cumbersome, so it’s still common to avoid them for convenience.

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