Re: `${PARAMETER:OFFSET}' does not work for negative offset

[Pierre Gaston]

On Fri, Feb 12, 2016 at 10:22 AM, Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de> wrote:

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc -I/home/abuild/rpmbuild/BUILD/bash-4.2 -L/home/abuild/rpmbuild/BUILD/bash-4.2/../readline-6.2
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-suse-linux-gnu' -DCONF_VENDOR='suse' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib   -fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g  -D_GNU_SOURCE -DRECYCLES_PIDS -Wall -g -Wuninitialized -Wextra -Wno-unprototyped-calls -Wno-switch-enum -Wno-unused-variable -Wno-unused-parameter -ftree-loop-linear -pipe -DBNC382214=0 -fprofile-use
uname output: Linux pc 4.1.15-8-default #1 SMP PREEMPT Wed Jan 20 16:41:00 UTC 2016 (0e3b3ab) x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-suse-linux-gnu

Bash Version: 4.2
Patch Level: 47
Release Status: release

Description:
    `${PARAMETER:OFFSET}' does not work for negative offset; the complete
    parameter value is substituted

    The bug goes back to at least bash 3.2...

Repeat-By:
    "X=ABC; echo ${X:-2}" outputs "ABC", and not "BC"

There is an ambiguity between ${param:-default} and ${param:n:m} when n is negative

${X:(-2)} or ${X: -2} (with space) are possible workarounds