Re: Encoding multiple filenames in a single variable

[Greg Wooledge]

On Mon, Aug 30, 2010 at 11:25:00PM +1000, Jon Seymour wrote:
> I am working on an extension to git, and need to store a list of shell
> files that can be used to extend the capabilities of the command I am
> writing. Most of the time, a variable of the form:
> 
> GIT_EXTRA_CONDITION_LIBS="libA.sh libB.sh" would work, but technically
> speaking, I do need to support spaces in the path (if nothing else,
> git's test suite cunningly runs within a directory that contains space
> in the name :-).

If this is an environment variable, then you're screwed.  Environment
variables can't be arrays, and if they could, they surely wouldn't be
portable.

> In the end, what I have done is make use of git's rev-parse --sq-quote
> feature to quote filenames that can contain spaces. That way, if you
> really want spaces in the filenames, you can have it, but if you
> don't, then you get the convenience of space as a separator.
> 
> So, for example:
> 
>     GIT_EXTRA_CONDITION_LIBS="libA.sh 'lib B.sh' libC.sh"

What does it do with filenames that contain apostrophes?  How do you
read the filenames back out of this format?  The only ways I can
think of off the top of my head to parse that kind of input in a
script are eval and xargs, and those should send you screaming....

There really is no good way to put multiple filenames into a single
environment variable.  Your best bet is to put them in a file and
make the environment variable point to that file.  The contents of
the file would have to be NUL-delimited or newline-delimited.  I'm
pretty sure that you'll end up going with newline delimiters and just
saying "if your filenames have newlines in them, you lose, so don't
do that".  Which is not the worst approach in the world.