ruby - Colon (:) appears as forward slash (/) when creating file name

Question

I am using date and time to label a new file that I'm creating, but when I view the file, the colon is a forward slash. I am developing on a Mac using 10.7+

Here is the code I'm using:

 File.open("#{time.hour} : 00, #{time.month}-#{time.day}-#{time.year}", "a") do |mFile|
        mFile.syswrite("#{pKey} - #{tKey}: 
") 
        mFile.syswrite("Items closed: #{itemsClosed} | Total items: #{totalItems} | Percent closed: % #{pClosed} 
") 
        mFile.syswrite("
")
        mFile.close
     end

Here is the output (assuming the time is 1pm):

13 / 00, 11-8-2012

Why is this happening and how can I fix it? I want the output to be:

13:00, 11-8-2012

Answer 1

Once upon a time, before Mac OS X, : was the directory separator instead of /. Apparently OS X 10.7 is still trying to fix up programs like that. I don't know how you can fix this, if you really need the : to be there. I'd omit it :-).

EDIT: After a bit more searching this USENIX paper describes what is going on. The rule they use apparently is this:

Another obvious problem is the different path separators between HFS+ (colon, ':') and UFS (slash, '/'). This also means that HFS+ file names may contain the slash character and not colons, while the opposite is true for UFS file names. This was easy to address, though it involves transforming strings back and forth. The HFS+ implementation in the kernel's VFS layer converts colon to slash and vice versa when reading from and writing to the on-disk format. So on disk the separator is a colon, but at the VFS layer (and therefore anything above it and the kernel, such as libc) it's a slash. However, the traditional Mac OS toolkits expect colons, so above the BSD layer, the core Carbon toolkit does yet another translation. The result is that Carbon applications see colons, and everyone else sees slashes. This can create a user-visible schizophrenia in the rare cases of file names containing colon characters, which appear to Carbon applications as slash characters, but to BSD programs and Cocoa applications as colons.