Colon/Asterisk as a filename delimiter?

Question

I'm looking for a character to use a filename delimiter (I'm storing multiple filenames in a plaintext string). Windows seems not to allow :, ?, *, <, >, ", |, / and \ in filenames. Obviously, \ and / can't be used, since they mean something within a path. Is there any reason why any of those others shouldn't be used? I'm just thinking that, similar to / or \, those other disallowed characters may have special meaning that I shouldn't assume won't be in path names. Of those other 7 characters, are any definitely safe or definitely unsafe to use for this purpose?

Answer 1

If all you need is the appearance of a colon, and will be creating it programatically, why not make use of a UTF-8 character that just looks like a colon?

My first choice would be the Modifier Letter (U+A789), as it is a typical RTL character and appears a lot like a colon. It is what I use when I need a full DateTime in the filename, such as file_2017-05-04_16꞉45꞉22_clientNo.jpg

I would stay away from characters like the Hebrew Punctuation Sof Pasuq (U+05C3), as it is a LTR character and may mess with how a system aligns the file name itself.

Answer 2

Why dont you use any character with ALT key combination like ‡ (Alt + 0135) as delimiter ?

Answer 3

It is actually possible to create files programmatically with every possible character except \. (At least, this was true at one time and it's possible that Windows has changed its policy since.) Naturally, files containing certain characters will be harder to work with than others.

What were you using to determine which characters Windows allows?

Update: The set of characters allowed by Windows is also be determined by the underlying filesystem, and other factors. There is a blog entry on MSDN that explains this in more detail.

Answer 4

The characters : and " are also used in paths. Colon is the drive unit delimiter, and quotation marks are used when spaces are part of a folder or file name.

The charactes * and ? are used as wildcards when searching for files.

The characters < and > are used for redirecting an application's input and output to and from a file.

The character | is used for piping output from one application into input of another application.

I would choose the pipe character for separating file names. It's not used in paths, and its shape has a natural separation quality to it.

An alternative could be to use XML in the string. There is a bit of overhead and some characters need encoding, but the advantage is that it can handle any characters and the format is self explanatory and well defined.

Answer 5

Windows uses the semicolon as a filename delimiter: ;. look at the PATH environment variable, it is filled with ; between path elements.

(Also, in Python, the os.path.pathsep returns ";", while it expands to ":" on Unix)

Answer 6

I have used * in the past. The reason for portability to Linux/Unix. True, technically it can be used on those fileysystems too. In practice, all common OSes use it as a wildcard, thus it's quite uncommon in filenames. Also, people are not surprised if programs do break when you put a * in a filename.