Re: null bytes in file names?

[Peter Stephenson <pws@csr.com>]

Erik Trulsson wrote:
> On Mon, Apr 07, 2003 at 10:32:21AM +0200, Dominik Vogt wrote:
> > As far as I know, UNIX file systems allow null bytes in file
> > names.  Out of curiosity I tried generating such a file.  I edited
> > a file fn in a hex editor and put a single null byte into it.
> 
> Your knowledge is somewhat faulty.
> There are exactly two characters that Unix does not allow in filenames.
> Those are NUL (ASCII code 0) and / (ASCII code 47).
> The former is used to indicate the end of a filename, while the latter
> is used to separate directory paths.

Just to be particular...

> > Take I (with "touch"):
> > 
> >   $ touch $(< fn)
> >   touch: creating `': No such file or directory
> >   touch: creating `': No such file or directory

...zsh actually handles the NUL internally, but there's no way to pass
it down as an argument to `touch'.  That gets passed a string `NUL
NUL'.  However, since as you no doubt know all the command receives is a
count of arguments and a series of null-terminated strings, touch simply
sees the first NUL.  The same would happen with an `open()' call from
within zsh.  That's where the rule Erik mentioned comes from.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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