On Wed, Jul 20, 2022 at 06:32:22PM +0100, Peter Maydell wrote:
> > > + # backslash escape any '\' and '"' characters
> > > + printf "%s" "$e" | sed -e 's/\([\"]\)/\\\1/g'
> >
> > You've fixed the bashism, but at the expense of a non-POSIX use of
> > sed. POSIX says the input to sed must be a text file (ending in a
> > newline; but $e does not), and as a result it always outputs a newline
> > (but you don't want a newline before the closing """). GNU sed
> > happens to do what you want for input not ending in a newline, but I
> > don't remember off-hand whether BSD sed does, and I know that Solaris
> > sed does not.
>
> I just copied the approach we already take in quote_sh:
>
> quote_sh() {
> printf "%s" "$1" | sed "s,','\\\\'',g; s,.*,'&',"
> }
>
> Is that also relying on this non-portable sed use?
Yep. And since no one has complained, BSD sed probably handles it the
way we want (input without a trailing line getting substituted and
re-output without a trailing newline).
If we cared, this one could also be fixed:
quote_sh() {
printf "'%s'" "$(printf '%s\n' "$1" | sed "s,','\\\\'',g")"
}
Also note that we are depending on $1 never containing newlines, because
this change would alter the existing:
$ quote_sh "a
c"
'a'
'c'
into:
$ quote_sh "a
c"
'a
c'
which is probably more what you wanted.
>
> > If this passes on BSD, then I'm okay with it; but if we want to avoid
> > non-POSIX altogether, this should work (using the shell's $() to strip
> > the trailing newline we added to keep sed happy):
> >
> > # backslash escape any '\' and '"' characters
> > printf '"""%s""",' "$(printf "%s\n" "$e" | sed -e '/s/\([\"]\)/\\\1/g')"
>
> Mmm.
Given that no one has complained about quote_sh, insisting on POSIX
compliance (with its resulting increase in line noise and length) is
not winning any maintainability arguments ;)
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
