Computer discoveries from February 2016

I found a text file named TIL.md lying around on my computer, with one section dated 17th February 2016. Apparently I’d planned to keep a log of the weird or interesting computer things I learned each day, but forgot after a day. I’d also forgotten all the facts in the file and was surprised afresh. Maybe you’ll be surprised too:

  • Windows’ shell and user interface do not support filenames with trailing spaces, so if you have a directory called worstever.christmas˽ (where ˽ represents a space) on your Unix fileserver, and serve it to Windows over SMB, you’ll see a filename like CQHNYI~0. I think this is the DOS-style 8.3 compatibility filename but I’m not sure where it gets generated in this case – Samba?
  • TIFF files can contain multiple images.
  • If you have a multi-subfile TIFF, multi.tiff, and run convert multi.tiff multi.jpeg, you will not get back a file called multi.jpeg; convert will silently assume you meant convert multi.tiff multi-%d.jpeg and give you back multi-0.jpeg, multi-1.jpeg, etc.

For some context: at the time, I was trying to work out why a script that imported a few tens of thousands of photographs into pan.do/ra – which doesn’t like TIFFs – had skipped some photographs, and imported others as a blank white rectangle; and why a Windows application pointed at the same fileserver showed a different number of photographs again. This was also the first time I encountered an inadvertent homoglyph attack: x.jpg and х.jpg are indistinguishable in most fonts.

One Reply to “Computer discoveries from February 2016”

  1. On the other hand, ls on the version of FreeBSD I was using (over ssh from an Ubuntu machine) rendered non-ASCII characters as backslash-escaped UTF-8-encoded bytes, which was really awful in a directory full of Cyrillic filenames but at least made the homoglyph problem very obvious.

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