Re: Shell script silently exits. Why?

[Cristian Ionescu-Idbohrn]

On Tue, 29 Nov 2016, Pavel A wrote:
>
> Is it possible to test for active option within ash script?
> My version of ash does not seem to recognize "test -o" or [ -o errexit ]

To test on errexit you'd do something like:

case $- in
*e*)
echo errexit set
;;
*)
echo errexit not set
;;
esac

The $- thing:

Special Parameters

 - (Hyphen.)  Expands to the current option flags (the single-letter
  option names concatenated into a string) as specified on
  invocation, by the set builtin command, or implicitly by the
  shell.


Cheers,

-- 
Cristian
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Re: Shell script silently exits. Why?

[Pavel A]

Apologies for late response and thanks for everyone who pointed to the behavior 
of let command with zero result. 

Is it possible to test for active option within ash script?
My version of ash does not seem to recognize "test -o" or [ -o errexit ]

Grepping my scripts does not find the -e option set. 
Anyway I'm replacing all let commands to $(()) based on opinion on 
StackOverflow that "let" is not posix-blessed. 

Thanks, 
Pavel A. 

> On 17 Nov 2016, at 17:49, Bastian Bittorf  wrote:
> 
> * Pavel A  [17.11.2016 16:47]:
>> We checked that the script does not contain weird unprintable characters and 
>> other obvious things. Just plain ascii.
> 
> try with 'set -x' ontop of your script and check the last lines when 
> executing it.
> also: does 'sh -n your_file.sh' complains?
> 
> bye, bastian
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Re: Shell script silently exits. Why?

[Ralf Friedl]

Arnout Vandecappelle wrote:

  I guess you have a 'set -e' somewhere in your script?

  let returns the value it computed, so if $foo is different from 0, it will
return non-0. This causes the shell to exit.

  It's POSIX behaviour.
Bash "let" returns 1 if there is a sytax error within the expression or 
the expression is zero, 0 otherwise. So it is basically a "not" 
operator, the opposite of what you describe.
I'm not sure there is a good reason for "let" to return an exit status 
depending on the value assigned, whether 0 is returned for a zero or a 
non-zero value assigned.


But bash does exit when let returns 1 and "-e" is set, so that might be 
the reason.


Regarding POSIX behaviour, the list of shell built-ins at 
http://pubs.opengroup.org/onlinepubs/007904875/idx/sbi.html doesn't even 
mention "let", and "let" can only implemented as a built-in as it must 
assign a value to a shell variable.

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Re: Shell script silently exits. Why?

[Arnout Vandecappelle]

On 17-11-16 16:43, Pavel A wrote:
> Dear experts,
> 
> We have a strange problem with ash script: the shell silently exits while 
> executing a script. It is likely caused by a "let" command. 
> Anyone seen similar behavior? How to debug it?
> 
> Busybox version is 1.22.1 (this is what it prints out, not sure about 
> configuration and build details). 
> The same script works well on busybox 1.16.0 
> Unfortunately this does not reproduce on small example. 
> 
> The failing place in the script looks like;
> Somefunc() {
>  local v
>  echo "this prints"
>  let "v = $foo & 0x000FFF "

 I guess you have a 'set -e' somewhere in your script?

 let returns the value it computed, so if $foo is different from 0, it will
return non-0. This causes the shell to exit.

 It's POSIX behaviour.

 Regards,
 Arnout

>  echo "this does not print"
> }
> 
> We checked that the script does not contain weird unprintable characters and 
> other obvious things. Just plain ascii. 
> 
> Best regards,
> pavel_a
> 
> 
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-- 
Arnout Vandecappelle  arnout at mind be
Senior Embedded Software Architect+32-16-286500
Essensium/Mindhttp://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium   BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
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Shell script silently exits. Why?

[Pavel A]

Dear experts,

We have a strange problem with ash script: the shell silently exits while 
executing a script. It is likely caused by a "let" command. 
Anyone seen similar behavior? How to debug it?

Busybox version is 1.22.1 (this is what it prints out, not sure about 
configuration and build details). 
The same script works well on busybox 1.16.0 
Unfortunately this does not reproduce on small example. 

The failing place in the script looks like;
Somefunc() {
 local v
 echo "this prints"
 let "v = $foo & 0x000FFF "
 echo "this does not print"
}

We checked that the script does not contain weird unprintable characters and 
other obvious things. Just plain ascii. 

Best regards,
pavel_a


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