[Tcsh] backslashed escape sequences in echo

[Michal Szymanski]

Hi, thanks for the explanation.

I think we do have here sort of "historical mess". The original SysV
echo(1) syntax suggesting \0ccc as an octal-coded character is quite
strange as it seems to be an jumble of the well-known C syntax for an
octal integer constant (0ccc) *and* an octal-escape-sequence (\ccc).
The latter has never required zero as the first digit. Surely a '0' is
an octal digit but the C syntax for octal escape sequence allows only
1 to 3 digits, so \0140 is not a valid C octal escape sequence.
Indeed, printf("\0140 \n") outputs a formfeed (reduced to a newline
in my terminal) followed by '0' and the final newline. Pretty much like the
new version of tcsh.

regards, Michal.

On Tue, Jul 02, 2024 at 01:12:20PM +0200, H.Merijn Brand wrote:
> On Tue, 2 Jul 2024 11:52:29 +0200, Michal Szymanski <msz at astrouw.edu.pl> wrote:
> 
> > Hi,
> > 
> > I've just noticed a changed behavior of 'echo' command with octal
> > \xxxx sequence. Most of the machines run Rocky Linux 8.10 with tcsh
> > 6.20.00. One of my aliases includes command (simplified here)
> >   echo "a \0140 b"
> > which has been working for years giving
> > a ` b
> > 
> > Now on my Ubuntu desktop recently upgraded to 24.04, coming (what a
> > coincidence :) with tcsh 6.24.10, this has broke and the output is now
> > a 
> >   0 b
> 
> That change happened between 6.23.00 and 6.23.01
> 38 commits (merge commits excluded)
> 
> I just verified that e6c9f58b10797e1b793c70782aad239f7087a037 (my work
> to improve Unicode support) is the cause.
> 
> https://github.com/tcsh-org/tcsh/commit/06915a414e185d314d5117b04ee460e441cbe962
> 
> > To get the previous behavior, I have to remove the 0, echo "a \140 b"
> > 
> > It works as such even if I change $echo_style from the default "both"
> > to "sysv" when it should, AFAIU, mimic the SYSV behavior of echo(1).
> > This is not true as the echo(1) requires 0 before 1 to 3 octal digits,
> > at least in the manual:
> > 
> >        \0NNN  byte with octal value NNN (1 to 3 digits)
> > 
> > In the real world, however, both versions give the octal-coded char:
> > 
> > >/usr/bin/echo -e "a \140 b"  
> > a ` b
> > >/usr/bin/echo -e "a \0140 b"  
> > a ` b
> > 
> > Is that to be expected? When was it introduced? I cannot find any
> > "Changelog" file in tcsh sources. There is "Fixes" file, and "BUGS"
> > file, but no Changelog. The most recent mention of 'octal' in "Fixes"
> > is from May 12, 2010 and refers to V6.17.02.
> > 
> > best, Michal
> > 
> 
> 
> -- 
> H.Merijn Brand  https://tux.nl   Perl Monger   http://amsterdam.pm.org/
> using perl5.00307 .. 5.37        porting perl5 on HP-UX, AIX, and Linux
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>                            



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-- 
  Michal Szymanski (msz at astrouw dot edu dot pl)
  Warsaw University Observatory, Warszawa, POLAND