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Subject: Re: Incrementing variable=0 with arithmetic expansion causes Return code = 1
Date: Fri, 28 Aug 2020 14:09:05 +0100
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On 28/08/2020 09:00, Gabriel Winkler wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc -I/home/abuild/rpmbuild/BUILD/bash-4.4 -L/home/abuild/rpmbuild/BUILD/bash-4.4/../readline-7.0
> 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-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g  -D_GNU_SOURCE -DRECYCLES_PIDS -Wall -g -Wuninitialized -Wextra -Wno-switch-enum -Wno-unused-variable -Wno-unused-parameter -Wno-parentheses -ftree-loop-linear -pipe -DBNC382214=0 -DIMPORT_FUNCTIONS_DEF=0 -fprofile-use -fprofile-correction
> uname output: Linux sophie 4.12.14-150.32-default #1 SMP Thu Aug 1 08:42:52 UTC 2019 (a2a3983) x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-suse-linux-gnu
> 
> Bash Version: 4.4
> Patch Level: 23
> Release Status: release
> 
> Description:
> If I have a variable with the value 0 assigned to it incrementing it causes the return code to be 1, even though the variable has been incremented successfully. This only happens if the value of the variable is 0. With positive and negative values this bug is no present.
> 
> Repeat-By:
> # Works fine
> test=1
> ((test++))
> echo $?
> 0
> echo $test
> 2
> 
> # Causes error
> test=0
> ((test++))
> echo $?
> 1
> echo $test
> 1

This isn't a bug. You should write ((++test)) if you want the 
post-incremented value to be evaluated.

-- 
Kerin Millar