Re: sh compatibility again :->

["Bart Schaefer" <schaefer@candle.brasslantern.com>]

On Aug 12,  4:18am, Zoltan Hidvegi wrote:
} Subject: Re: sh compatibility again :->
}
} Andrej Borsenkow wrote:
} [...]
} > 1. It doesn't like malformed constructs like
} > 
} > A="`cat /some/file"    (note missed backtick)
} > 
} > zsh tries to parse command substitution behind closing double-quote, and
} > ends up with `missing "' at the end of script. Our /bin/sh stops at
} > closing double-quote. In POSIX the result is undefined - thus, techically
} > neither violate it. 
} 
} I copied the behaviour of bash here.  pdksh also behaves this way.

Right; if I recall correctly, bash and ksh both permit stuff like:

$ echo "foo `echo "bar baz"` boing"

That is, bash and ksh nest double quotes inside backticks.  Old-fashioned
Bourne shell, on the other hand, does NOT permit nesting of double quotes,
even inside backticks.  So in bash/ksh the above is parsed as

	(echo) (foo `echo "bar baz"` boing)

but in sh it is

	(echo) (foo `echo bar) (baz` boing)

The only way to resolve this would be with yet another option, SH_QUOTES
or some such.  Worth it?  Dunno.

} > But the following things could probably be fixed 
} > 
} > 4. Traditional /bin/sh interprets `set -' as set +xv.
} 
} OK.  I've changed that.  set - will be the same as set +xv and
} set - args will be the same as set +xv -- args.

Hmm.  So what's the approved way of setting $1 to "-x"?  `set -- -x`?
And is `set --` equivalent to `shift $#`, since `set -` is not?

Are you sure `set - args` should act like `set +xv -- args`?

I can't say I'm entirely excited about this change.

} > 5. Currently zsh sets BSD_ECHO when running as sh. Our sh does support
} > escapes in echo; I recall that SCO sh does it as well. I don't know about
} > others. What about relaxing it? If scripts doesn't rely upon escapes in
} > echo, it would make no harm.
} 
} I'll try to write a configure check for the echo style of /bin/sh and use
} that.

Eww, no.  Let's pick one behavior and stick with it, please.  The default
options, even in an emulation mode, shouldn't vary from one installation
to the next!  It's been a long time since I encountered an sh that didn't
have a builtin SysV-style echo -- BSD_ECHO is needed mostly for csh
compatibility.  I'd vote for leaving BSD_ECHO off when run as "sh".

-- 
Bart Schaefer                             Brass Lantern Enterprises
http://www.well.com/user/barts            http://www.nbn.com/people/lantern

New male in /home/schaefer:
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