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Asked: 2010-06-13 13:24:38 +0800 CST

Linux/Windows/Unix/... file names: Which characters are allowed? Which are unescaped?

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Which characters are allowed and which of them must be escaped on the command line in different operating systems?

windows linux filesystems command-line-interface

4 Answers

  1. Best Answer

    There's a discussion of filename characters in the Wikipedia article on File Names.

    You may find this essay informative: Fixing Unix/Linux/POSIX Filenames.

    This article compares OS X and Windows XP: X vs. XP: Forbidden Characters in Filenames (PDF, see pp approx. 64-66).

    Things That Shouldn’t Be in File Names for $1,000 Alex

    I don't know which characters must be un-escaped, but in Linux, it's probably not a good idea to escape the characters that may have special meaning such as "n" (newline), "t" (tab) and others, but that's generally not a problem in file operations. Perhaps you mean "escaped" rather than "unescaped". The most common ones are ones that the shell will interpret such as space, ">", "<", etc. See some of the articles I linked for a discussion of those.

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  2. The only characters not allowed in a filename in *nix are NUL and /. In Windows, only NUL, :, and \ are truly not allowed, but many apps restrict that further, also preventing ?, *, +, and %.

    At no point do any characters in a filename need to be escaped except as required in order to not be interpreted by the shell.

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  3. If you create a file on Windows with Explorer using one of the following characters, it will complain that the characters are not allowed:

    \ / : * ? " < > |

    A good reference is here:

    Naming Files, Paths, and Namespaces
    http://msdn.microsoft.com/en-us/library/aa365247%28VS.85%29.aspx

    Microsoft further states:

    "... on Windows-based desktop platforms, invalid path characters might include ASCII/Unicode characters 1 through 31, as well as quote ("), less than (<), greater than (>), pipe (|), backspace (\b), null (\0) and tab (\t)."

    http://msdn.microsoft.com/en-us/library/system.io.path.getinvalidpathchars.aspx

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  4. On Linux and other POSIX compatible systems, "/" is reserved as it's the directory separator, and "\0" (the NULL character) designates the end of the string. Everything else is allowed.

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