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Re: [Parameter substring expansion not work for negative offset]


From: Dennis Williamson
Subject: Re: [Parameter substring expansion not work for negative offset]
Date: Sun, 8 Sep 2013 11:21:56 -0500

On Sep 8, 2013 10:44 AM, "hanzlik" <address@hidden> wrote:
>
> Configuration Information:
> Machine: i686
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i686'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i686-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
-DRECYCLES_PIDS -DDEFAULT_PATH_VALUE='/usr/local/bin:/usr/bin'
-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=i686 -mtune=atom
-fasynchronous-unwind-tables
> uname output: Linux franta.hanzlici.cz 3.10.10-200.fc19.i686.PAE #1 SMP
Thu Aug 29 19:16:15 UTC 2013 i686 i686 i386 GNU/Linux
> Machine Type: i686-redhat-linux-gnu
>
> Bash Version: 4.2
> Patch Level: 45
> Release Status: release
>
> Description:
> As I understand bash man page, using negative offset in substring
expansion
>  ${parameter:offset} / ${parameter:offset:length}
> then offset shoul be taken as offset from the parameter value string.
> Thus, e.g. ${A:-1} or ${A:-1:1} should return last character from $A
string.
> But this construct return me all $A string.
>
> Repeat-By:
> $ A="abcd0"; E1=${A:-1:1}; E2=${A:-1}; echo "A=$A, E1=$E1, E2=$E2."
> A=abcd0, E1=abcd0, E2=abcd0.
>
> # I expect result E1==E2=="0", right?
>
> Sorry if I made some mistake here.
> With regards, Franta Hanzlik <address@hidden>
>
The man page says "Note that a negative offset must be separated from the
colon by at least one space..."


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