Python surpasses Perl in popularity?

[Xah Lee]

Great to see quality post from real expert once in a while. Thanks!

  Xah
∑ http://xahlee.org/

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On Nov 29, 9:03 am, Stephane CHAZELAS <stephane_chaze... at yahoo.fr>
wrote:
> There's a common confusion in this in the nature of /bin/sh.
> There's no standard (neither POSIX nor Unix) that specifies that
> /bin/sh should be any variant of the Bourne shell. Over the
> years and on the different flavours of Unix, /bin/sh has been a
> Thomson shell, Mashey shell, Bourne shell and all its variants,
> Almquist shell, bash, ksh, zsh...
>
> For a very long time, on a wide range of Unices, it has been the
> Bourne shell (modified slightly in different ways by the
> different Unix vendors), so that's probably why it is still
> nowadays confused with the Bourne shell even though it is still
> so only on very few Unices (mainly only Solaris, Tru64 and some
> SCO OSes).
>
> Nowadays, what the POSIX and Unix standards say is that a conformant Unix
> should have somewhere (and the location is not specified but on
> most Unices except those quoted above is generally /bin) a
> command called "sh" that is an interpreter of the POSIX shell
> language it defines.
>
> Shells that do implement an interpreter for that language
> (though most shells of course have extensions which the
> specification doesn't prohibit, such as many C compilers (like
> gcc) have extensions to the standard C language as published by
> the ISO) include (with lesser or greater accuracy) bash (2 or
> above), the AT&T Korn shell (88<x> or 93<x> versions) and its
> variants, the public domain Korn shell and its derivatives such
> as posh, mksh or OpenBSD sh, modern variants of the Almquist
> shell such as the NetBSD sh or dash.
>
> That shell language is based on a subset of the ksh88 language
> and the Bourne shell is not a conformant implementation. Amongst
> the feature of the POSIX/Unix sh that are not in the Bourne
> shell are the $(...) form of command substitution, arithmetic
> expansions as in $((...)), the processing of IFS that differs,
> redirections of compound commands that no longer invoke a
> subshell... That language is mostly backward compatible with the
> Bourne syntax though there are a few small differences.
>
> To sum up, /bin/sh is no longer the Bourne shell. It is only so
> on very old systems and on systems that have chosen to keep the
> Bourne shell as /bin/sh for backward compatibility (and for
> those, the standard sh is in another place such as
> /usr/xpg4/bin on Solaris). Free software Unices have never had
> the Bourne shell as their /bin/sh as the source code of the
> Bourne shell has not been released until recently (except for
> some early versions of BSD and they were then breaching the
> law).
>
> --
> Stéphane