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Re: typeset -r prevents local variable of same name.


From: Clark J. Wang
Subject: Re: typeset -r prevents local variable of same name.
Date: Thu, 17 Feb 2011 12:08:59 +0800

On Thu, Feb 17, 2011 at 11:13 AM, Chet Ramey <address@hidden> wrote:

> On 2/13/11 3:17 PM, address@hidden wrote:
> > Configuration Information [Automatically generated, do not change]:
> > Machine: i386
> > OS: linux-gnu
> > Compiler: gcc
> > Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i386'
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i386-redhat-linux-gnu'
> -DCONF_VENDOR='redhat' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash'
> -DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -D_GNU_SOURCE
> -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g -pipe -Wall
> -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector
> --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic
> -fasynchronous-unwind-tables
> > uname output: Linux saturn.syslang.net 2.6.27.41-170.2.117.fc10.i686.PAE
> #1 SMP Thu Dec 10 10:48:30 EST 2009 i686 athlon i386 GNU/Linux
> > Machine Type: i386-redhat-linux-gnu
> >
> > Bash Version: 3.2
> > Patch Level: 39
> > Release Status: release
> >
> > Description:
> >       First, I already submitted this bug from work, but I didn't
> >  realize that the address I sent from would not be allowed to receive
> >  a response. This address will work fine.
> >
> > If I declare a variable at the top scope using -r, it will prevent me
> > from declaring a local copy in a subroutine. This problem happens in
> > this version of bash as well as in bash4 under Fedora 14.
>
> This is intentional.  A variable is declared readonly for a reason, and
> readonly variables may not be assigned to.  I don't believe that you
> should be able to use a function to circumvent this.
>
> That makes little sense to me. I don't see any disadvantages if a local var
is allowed to use the same name as a global readonly var. And with current
bash behavior we may see var name collisions even with the local keyword.

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


-- 
Clark


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