Re: [PATCH] test: Fix printf error when debug is enabled

[Yumei Huang <yuhuang@redhat.com>]

On Tue, Sep 30, 2025 at 8:23 AM David Gibson
<david@gibson.dropbear.id.au> wrote:
>
> On Tue, Sep 30, 2025 at 12:24:17AM +0200, Stefano Brivio wrote:
> > On Mon, 29 Sep 2025 14:30:14 +0800
> > Yumei Huang <yuhuang@redhat.com> wrote:
> >
> > > Running test pasta/tcp with debug enabled would get stuck with
> > > below error:
> > >
> > >   + printf 'DEBUG: ns     socat -u OPEN:__BASEPATH__/big.bin TCP6:[__GW6__%__IFNAME__]:10003\n'
> > >   lib/term: line 38: printf: `_': invalid format character
> > >
> > > The error occurs because printf interprets the % character as the
> > > start of a format specifier, and the following '_' isn't one of
> > > them.
> > >
> > > Fix it by replacing 'printf "${*}\n"' with 'printf "%s\n" "$*"'.
> >
> > I'm not sure why, but this breaks colour highlights for me. Instead of
> > seeing a part of this message in blue, now I get:
> >
> >   Test layout: \033[1;34msingle passt instance with guest\033[0m.\n
> >
> > I can look into it if it only happens for me, or if needed.
>
> Oh, that's interesting.  I believe the colouring has been broken
> forever on Fedora, but I never got around to looking into it.

Well, the color worked fine on fedora before I changed to using "%s".

> Figuring this out might reveal why.  Maybe.
>
> I realised I think I know why: those colour codes rely on turning
> "\033" into a terminal escape.  printf(1) will do that in the format
> string, but not in %s parameters
>
>         $ printf "a\tb%sc\n " "\t"
>         a       b\tc
>
> We can fix this either by moving the escape codes back into the format
> string, or using %b instead of %s, which explicitly interprets string
> escape codes.

Yes, %b fixes this.

I will send v2 to update it and the brackets. Thanks.

>
> --
> David Gibson (he or they)       | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au  | minimalist, thank you, not the other way
>                                 | around.
> http://www.ozlabs.org/~dgibson



-- 
Thanks,

Yumei Huang