Bug#812215: consider spliting systemd-tmpfiles into separate package

[Josh Triplett]

On Mon, Feb 01, 2016 at 04:24:21PM +0100, Ondřej Surý wrote:
> Hi Michael,
> 
> I never bothered to implement more than 'd', but I am happy to
> contribute my sysvrc shell snippet I use as replacement for systems
> without systemd-tmpfiles installed. 
> 
> ```
> do_tmpfiles() {
>     local type path mode user group age argument
>     if [ -r "$1" ]; then
>         if [ -x /bin/systemd-tmpfiles ]; then
>             /bin/systemd-tmpfiles --create "$1"
>         else
>             while read type path mode user group age argument; do
>                 case "$type" in
>                     d)
>                         mkdir -p "$path";
> 			chmod "$mode" "$path";
>                         chown "$user:$group" "$path";
>                         ;;
>                     \#*)
>                         ;;
>                     *)
>                         log_warning_msg "tmpfile.d type '$type' is not
>                         supported yet"
>                         ;;
>                 esac
>             done < "$1"
> 	fi
>     else
>         log_warning_msg "tmpfiles.d file '$1' doesn't exist or is not
>         readable"
>     fi
> }
> ```
> 
> It should be fairly easy to implement the most common stuff used in
> Debian.

Implementing the various operation letters makes up half the problem.
The other half involves handling the various tmpfiles.d directories and
the precedence between them.  That includes the usual "override files
with the same filename" mechanism, but also:

> All configuration files are sorted by their filename in lexicographic
> order, regardless of which of the directories they reside in. If
> multiple files specify the same path, the entry in the file with the
> lexicographically earliest name will be applied. All other conflicting
> entries will be logged as errors. When two lines are prefix and suffix
> of each other, then the prefix is always processed first, the suffix
> later. Lines that take globs are applied after those accepting no
> globs. If multiple operations shall be applied on the same file, (such
> as ACL, xattr, file attribute adjustments), these are always done in
> the same fixed order. Otherwise, the files/directories are processed
> in the order they are listed.

That logic seems relatively straightforward (though fiddly) to implement
in a language with associative arrays, such as bash or Python, but not
in a language without them, such as POSIX sh.