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Re: Parameter expansion oddity


From: Chet Ramey
Subject: Re: Parameter expansion oddity
Date: Tue, 08 Jul 2003 09:48:10 -0400

> Configuration Information [Automatically generated, do not change]:
> Machine: i386
> OS: linux-gnu
> Compiler: i386-redhat-linux-gcc
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i386' 
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i386-redhat-linux-gnu' 
> -DCONF_VENDOR='redhat' -DSHELL -DHAVE_CONFIG_H  -I.  -I. -I./include -I./lib 
> -D_GNU_SOURCE  -O2 -g -pipe -march=i386 -mcpu=i686
> uname output: Linux meme.surrey.redhat.com 2.4.20-13.9 #1 Mon May 12 10:55:37 
> EDT 2003 i686 i686 i386 GNU/Linux
> Machine Type: i386-redhat-linux-gnu
> 
> Bash Version: 2.05b
> Patch Level: 0
> Release Status: release
> 
> Description:
>       ${VAR:+WORD} may be replaced by the expansion of WORD.  But there
>       seems to be no way of creating double quotes in this expansion, since
>       both quote removal and escaping behave oddly.

Are you wedded to using here documents?  Remember that here-docs are expanded
as if the contents occur within double quotes, but that double quotes within
the document aren't treated specially.

> Repeat-By:
>       Trying to get output: "bar"

echo "${FOO:+\"$FOO\"}"
echo ${FOO:+\"$FOO\"}
echo ${FOO:+'"'$FOO'"'}

all echo `"bar"'.

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
( ``Discere est Dolere'' -- chet )

Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/




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