Which characters are invalid for an ext3 filename? I imagine that at least / is an invalid character and probably \0. Is there an official list somewhere?

I'm not exactly sure where to look for this information, so please tell me where you found it.


2 Answers 2


Just those two.

From the wikipedia page on ext3:

Allowed characters in filenames - All bytes except NULL and '/'

  • Ah, I didn't see the stats at the side of the wikipedia page. Thanks!
    – User1
    Dec 1, 2010 at 21:26

/ seems to be allowed, at least on ext3 (supposedly in all, ext, ext2 & ext3 at least, likely also ext4) - just try this:

f='test/file'; echo "Test: '${f}'"
for c in touch ll rm ;do
eval "${c} '${f}'"

That will create "test/file", surprised me too... It will create it, show it with ls command and finally remove it with rm

You can type it on one line in bash:

$ f='test/file';for c in touch ll rm ;do eval "${c} '${f}'";done

So / seems to be (bizerrely) allowed in filenames - probably many tools can get confused with such though...

  • Cool trick, though probably ill-advised on production systems :-)
    – voretaq7
    Oct 19, 2012 at 18:58
  • Errr… do you have a directory called 'test'? That'll make a difference: touch: cannot touch 'test/file': No such file or directory
    – MikeyB
    Oct 19, 2012 at 19:35
  • Though useful as a joke to pull on one's assistants.
    – Magellan
    Oct 19, 2012 at 20:05
  • No just managed to create a file named "test/file" - would be interesting to try it with existing directory named test... It might not even give trouble, after all, the / at the end of directory name isn't really part of it's name... So I could imagine them actually working together... It'll look confusing though... Or did you mean you actually tried it? :)
    – robsku
    Jul 22, 2014 at 13:10

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