What characters are forbidden in Windows and Linux directory names?

Question

I know that / is illegal in Linux, and the following are illegal in Windows (I think): * . " / \ [ ] : ; | = ,

What else am I missing?

I need a comprehensive guide, however, and one that takes into account double-byte characters. Linking to outside resources is fine with me.

I need to first create a directory on the filesystem using a name that may contain forbidden characters, so I plan to replace those characters with underscores. I then need to write this directory and its contents to a zip file (using Java), so any additional advice concerning the names of zip directories would be appreciated.

Answer 1

The only illegal characters in modern filesystems are the directory separator (/ or \) and the NUL byte (\0).

Answer 2

Windows has several restrictions on file names; not only are characters like *, ", ? and others forbidden, there are several reserved names like PRN and CON, and several length restrictions. The full list is on MSDN.

Answer 3

There's a nice table covering the file naming rules for various operating systems here. (part of the wiki article "Filename").

Answer 4

Here you have ALL File/Folder naming rules for windows: http://www.portfoliofaq.com/pfaq/FAQ00352.htm

and here you have ALL for linux: http://www.cyberciti.biz/faq/linuxunix-rules-for-naming-file-and-directory-names/

Answer 5

Well, if only for research purposes, then your best bet is to look at this Wikipedia entry on Filenames.

If you want to write a portable function to validate user input and create filenames based on that, the short answer is don't. Take a look at a portable module like Perl's File::Spec to have a glimpse to all the hops needed to accomplish such a "simple" task.

Answer 6

Under Linux and other Unix-related systems, there are only two characters that cannot appear in a directory name, and those are NUL '\0' and slash '/'. The '/', of course, can appear in a path name.

Rumour¹ has it that Steven Bourne (of 'shell' fame) had a directory containing 254 files, one for each single letter (character code) that can appear in a file name. It was used to test the Bourne shell, and routinely wrought havoc on unwary programs such as backup programs.

Other people have covered the Windows rules.

Note that MacOS X has a case-insensitive file system.

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¹ I think it was Kernighan & Pike in 'The Practice of Programming' who said as much; it may have been in a related book (possibly even 'The UNIX Programming Environment').