Re: [Haskell-cafe] [offtopic] UNIX Shell (was: GHC RTS question)
On Feb 24, 2010, at 05:19 , Roman Cheplyaka wrote:
Well, this agrees with POSIX. So still I don't see the difference
between "$@" and ${1+"$@"}.
The difference is that Unix /bin/sh predates POSIX, and on systems
that usefully support a notion of backward compatibility (nostly
commercial, because (1) they have installed user bases that predate
POSIX and (2) they actually think it's worthwhile to support said user
bases) /bin/sh uses the traditional behavior that "$@" expands to ""
if there are no arguments. (This is "stupid" but consistent, another
concept that seems to have been thrown to the wolves.)
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com
system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu
electrical and computer engineering, carnegie mellon universityKF8NH
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Re: [Haskell-cafe] [offtopic] UNIX Shell (was: GHC RTS question)
Quoth Roman Cheplyaka ,
...
> Well, this agrees with POSIX. So still I don't see the difference
> between "$@" and ${1+"$@"}.
Whatever the standards etc. may say, I believe "$@" is reliably the
same as ${1+"$@"}, for old Bourne shells and new.
Donn
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Re: [Haskell-cafe] [offtopic] UNIX Shell (was: GHC RTS question)
* Magnus Therning [2010-02-24 09:11:54+]
> On Wed, Feb 24, 2010 at 07:18, Roman Cheplyaka wrote:
> > * Brandon S. Allbery KF8NH [2010-02-24 00:02:12-0500]
> >> On Feb 22, 2010, at 03:36 , Roman Cheplyaka wrote:
> >> >* Anthony Cowley [2010-02-21 14:15:00-0500]
> >> >>#! /usr/bin/env bash
> >> >>./prog --RTS $*
> >> >
> >> > ./prog --RTS "$@"
> >> >
> >> >Otherwise it will work wrong if arguments contain quoted field
> >> >separators (e.g. spaces).
> >>
> >>
> >> #! /bin/sh
> >> ./prog --RTS ${1+"$@"}
> >>
> >> The longer specification above should work with whatever /bin/sh is
> >> around, whether it's Solaris /sbin/sh, FreeBSD's sh, general Linux
> >> bash, Debian/Ubuntu dash, etc.
> >
> > Are you referring to some Solaris shell bug?
> >
> > Under POSIX these constructs seem to be equivalent.
> > "If there are no positional parameters, the expansion of '@' shall
> > generate zero fields, even when '@' is double-quoted."
>
> I believe he's referring to the following bit (taken from bash's man page):
>
> @ Expands to the positional parameters, starting from one. When the expansion
> occurs within double quotes, each parameter expands to a separate word.
> That
> is, "$@" is equivalent to "$1" "$2" ... If the double-quoted expansion
> occurs within a word, the expansion of the first parameter is joined with
> the beginning part of the original word, and the expansion of the last
> parameter is joined with the last part of the original word. When there are
> no positional parameters, "$@" and $@ expand to nothing (i.e., they are
> removed).
Well, this agrees with POSIX. So still I don't see the difference
between "$@" and ${1+"$@"}.
--
Roman I. Cheplyaka :: http://ro-che.info/
"Don't let school get in the way of your education." - Mark Twain
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Re: [Haskell-cafe] [offtopic] UNIX Shell (was: GHC RTS question)
On Wed, Feb 24, 2010 at 07:18, Roman Cheplyaka wrote:
> * Brandon S. Allbery KF8NH [2010-02-24 00:02:12-0500]
>> On Feb 22, 2010, at 03:36 , Roman Cheplyaka wrote:
>> >* Anthony Cowley [2010-02-21 14:15:00-0500]
>> >>#! /usr/bin/env bash
>> >>./prog --RTS $*
>> >
>> > ./prog --RTS "$@"
>> >
>> >Otherwise it will work wrong if arguments contain quoted field
>> >separators (e.g. spaces).
>>
>>
>> #! /bin/sh
>> ./prog --RTS ${1+"$@"}
>>
>> The longer specification above should work with whatever /bin/sh is
>> around, whether it's Solaris /sbin/sh, FreeBSD's sh, general Linux
>> bash, Debian/Ubuntu dash, etc.
>
> Are you referring to some Solaris shell bug?
>
> Under POSIX these constructs seem to be equivalent.
> "If there are no positional parameters, the expansion of '@' shall
> generate zero fields, even when '@' is double-quoted."
I believe he's referring to the following bit (taken from bash's man page):
* Expands to the positional parameters, starting from one. When the expansion
occurs within double quotes, it expands to a single word with the value of
each parameter separated by the first character of the IFS special
variable. That is, "$*" is equivalent to "$1c$2c...", where c is the first
character of the value of the IFS variable. If IFS is unset, the parameters
are separated by spaces. If IFS is null, the parameters are joined without
intervening separators.
@ Expands to the positional parameters, starting from one. When the expansion
occurs within double quotes, each parameter expands to a separate word. That
is, "$@" is equivalent to "$1" "$2" ... If the double-quoted expansion
occurs within a word, the expansion of the first parameter is joined with
the beginning part of the original word, and the expansion of the last
parameter is joined with the last part of the original word. When there are
no positional parameters, "$@" and $@ expand to nothing (i.e., they are
removed).
/M
--
Magnus Therning(OpenPGP: 0xAB4DFBA4)
magnus＠therning．org Jabber: magnus＠therning．org
http://therning.org/magnus identi.ca|twitter: magthe
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[Haskell-cafe] [offtopic] UNIX Shell (was: GHC RTS question)
* Brandon S. Allbery KF8NH [2010-02-24 00:02:12-0500]
> On Feb 22, 2010, at 03:36 , Roman Cheplyaka wrote:
> >* Anthony Cowley [2010-02-21 14:15:00-0500]
> >>#! /usr/bin/env bash
> >>./prog --RTS $*
> >
> > ./prog --RTS "$@"
> >
> >Otherwise it will work wrong if arguments contain quoted field
> >separators (e.g. spaces).
>
>
> #! /bin/sh
> ./prog --RTS ${1+"$@"}
>
> The longer specification above should work with whatever /bin/sh is
> around, whether it's Solaris /sbin/sh, FreeBSD's sh, general Linux
> bash, Debian/Ubuntu dash, etc.
Are you referring to some Solaris shell bug?
Under POSIX these constructs seem to be equivalent.
"If there are no positional parameters, the expansion of '@' shall
generate zero fields, even when '@' is double-quoted."
--
Roman I. Cheplyaka :: http://ro-che.info/
"Don't let school get in the way of your education." - Mark Twain
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