Re: Incrementing variable=0 with arithmetic expansion causes Return code = 1

[Chris Elvidge]

On 28/08/2020 09:00 am, 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
>
>
> ​Best Regards
>
> Gabriel Winkler
>
> _________________________
>
> bpm consult ag
> beeline solutions
> Gabriel Winkler
> DevOps Engineer
> Industriestrasse Ost 10
> CH-4614 Hägendorf
>
> Telefon +41 61 417 10 68
> Web     www.bpm.ch<http://www.bpm.ch/>

From man bash:

((expression))
The expression is evaluated according to the rules described
below under ARITHMETIC EVALUATION.  If the value of the
expression is non-zero, the return status is 0; otherwise the
return status is 1.  This is exactly equivalent to
let "expression".



--
Chris Elvidge
England