Re: Why&how do "sh" and "ksh" differ in behavior e.g. PS1 presentation, while their binaries are equal?

On Wednesday, October 31, 2018 10:19 PM, Joseph Mayer <joseph.mayer@protonmail.com> wrote:

> On Tuesday, October 30, 2018 4:33 PM, Sebastien Marie semarie@online.fr wrote:
>
> > On Tue, Oct 30, 2018 at 08:11:24AM +0000, Joseph Mayer wrote:
> >
> > > On a quick sourcecode check I didn't see any code paths e.g.
> > > "if (argv[0] matches "ksh") { something } else { something else }"
> > > however I presume I missed something.
> >
> > yes, the check was too quick, it seems :)
> > src/bin/ksh/main.c
> > 134 int
> > 135 main(int argc, char *argv[])
> > 136 {
> > 137 int i;
> > 138 int argi;
> > 139 Source *s;
> > 140 struct block *l;
> > 141 int restricted, errexit;
> > 142 char *wp;
> > 143 struct env env;
> > 144 pid_t ppid;
> > 145
> > 146 kshname = argv[0];
> > 147
> > ...
> > 236 / Check to see if we're /bin/sh. */237 if (!strcmp(kshname, "sh") || !strcmp(kshname, "-sh") ||
> > 238 (strlen(kshname) >= 3 &&
> > 239 !strcmp(&kshname[strlen(kshname) - 3], "/sh"))) {
> > 240 Flag(FSH) = 1;
> > 241 version_param = "SH_VERSION";
> > 242 }
> > 243
> >
> > Sebastien Marie
>
> Hi Sebastien,
>
> Thanks a lot for clarifying.
>
> sh's man page (http://man.openbsd.org/sh#DESCRIPTION) says:
>
> "This version of sh is actually ksh in disguise. As such, it also
> supports the features described in ksh(1). This manual page describes
> only the parts relevant to a POSIX compliant sh."
>
> When I read that originally, I perceived it as that "sh" and "ksh"
> normally would have equivalent behavior - which also seems logical
> given that their binaries are byte-equivalent.
>
> The meaning I gather from the sentence is that sh and ksh are
> equivalent and that instead the man pages will describe different
> functionalities that are actually available in both.
>
> Can that phrase in sh's man page be tweaked so that my misunderstanding
> no longer is possible?
>
> Do you find my misunderstanding a reasonable reading?
>
> Joseph

Moving this to bugs@ , sorry for spam.