Re: 3. Basic Shell Features versus POSIX features

[Chet Ramey]

Marc Herbert wrote:
> Hi,
> 
>  I more or less assumed that section "3. Basic Shell Features" is all
> POSIX, in contrast to section "6. Bash Features" which starts like this:
> "This section 6 describes features unique to Bash."

Not really.  The basic shell features are just that: the programming and
expansion constructs that allow you to use the shell and write shell
programs.

> I think I was wrong. There seems to be at least two non-POSIX features
> documented in the "Basic" section (brace expansion and process
> substitution).

Because all of the expansions should be documented together.  It would
reduce the manual's usefulness considerably if the expansions, which are
performed in sequence, were split across sections.

> Does the manual make any attempt to draw a line between POSIX and
> non-POSIX features? Does the "unique to bash" introduction sentence
> really make sense since most of these features are also found in other
> shells? Thanks in advance...

The bash documentation describes bash.  Its features are a superset
of the Posix feature set.  The manual attempts only to document what
changes when bash is in Posix mode.  If you want a description of what
Posix specifies, you can find it online:

http://www.opengroup.org/onlinepubs/9699919799/nfindex.html

The intent is that bash, with the correct set of options, implements
everything there in a conforming fashion, and provides additions beyond
what Posix specifies.

While some of the features in section 6 have been adopted by other shells
(or adopted from other shells) since the introductory sentence was written,
the section as a whole still documents the most-often-encountered places,
besides builtin commands unique to or extended in bash, where users will
find differences.

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/