Re: IFS=':' set -- aa:bb:cc:dd # Fails to set "$@"

[Chris F.A. Johnson]

On Wed, 1 Dec 2010, steveo@syslang.net 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:
>         It may be me, but I tried something that I thought should work, but it 
> does not. I want to use the set command to parse data and I want the IFS 
> variable to be in force during the set command. This does not work. So far, 
> every other use of
> var=val cmd
> seems to work fine. Only this one plays funny.
>
> Repeat-By:
>         IFS=':' set -- aa:bb:cc:dd
>         echo $1
>         # After this runs, $1 is aa:bb:cc:dd instead of aa
>         Instead, I have to say something like:
>         oldIFS="$IFS"
>         IFS=':'
>         set -- aa:bb:cc:dd
>         IFS="$oldIFS"
>
>         BTW, the same behavior happens in bash4.
>
> Fix:
>         Offered in the constructive spirit to see if this needs to be fixed or 
> if this is a deliberate or known behavior.

   That is the way it should behave.

   The line is parsed before IFS is set.

--
   Chris F.A. Johnson, <http://cfajohnson.com>
   Author:
   Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress)
   Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress)