Re: s6-log run script

From: Jan Olszak <jan.olszak_at_vestiacom.com>
Date: Fri, 4 Mar 2016 23:15:59 +0100

But what if I need to fallback if the arguments are malformed?

So something like - if some operation fails run another command, but if it
succeeds exit.


On Fri, Mar 4, 2016 at 11:06 PM, Jan Olszak <jan.olszak_at_vestiacom.com>
wrote:

> And this works perfectly.
> I missed the -D option in backtick. :)
>
> Yeah, /opt was just an example.
>
> Thanks!
>
> On Thu, Mar 3, 2016 at 2:09 AM, Laurent Bercot <ska-skaware_at_skarnet.org>
> wrote:
>
>> On 02/03/2016 23:52, Jan Olszak wrote:
>>
>>> #!/usr/bin/execlineb -P
>>> if -nt
>>> {
>>> backtick -n S6_LOG_ARGS
>>> {
>>> redirfd -r 0 /opt/s6logargs.opts s6-cat
>>> }
>>> import -u S6_LOG_ARGS s6-log T $S6_LOG_ARGS
>>> }
>>> s6-log T s1000000 n10 /var/log/syslogd
>>>
>>
>> That won't work for several reasons:
>>
>> * the if -nt will only return once s6-log returns. Since s6-log is a
>> long-lived program, that won't happen unless there's an error in the
>> s6-log invocation. Which is what is happening here.
>>
>> * execline is not like the shell: when you import S6_LOG_ARGS, it is
>> evaluated as just one word - it's not split. So your s6-log invocation
>> is given two arguments: T, and whatever is in S6_LOG_ARGS. Likely
>> s6-log cannot interpret the contents of your opts file as one single
>> argument, so it fails - and dies, and if returns, and you get the
>> fallback.
>>
>> * Even if s6-log succeeded, you'd have the "if" process hanging around,
>> and s6-log would be a child of if. That's not what you want: you always
>> want the process to execute into your chosen avatar of s6-log in the end.
>>
>> Try something like this:
>>
>> -----
>> backtick -n -D "s1000000 n10 /var/log/syslogd" S6_LOG_ARGS
>> {
>> redirfd -r 0 /opt/s6logargs.opts s6-cat
>> }
>> import -u -s S6_LOG_ARGS # notice the -s, to split the args
>> s6-log T ${S6_LOG_ARGS}
>> -----
>>
>> Also, traditionally, /opt is not a good place to store regular files,
>> even global ones - you'd use /etc or a subdirectory of /etc for that.
>> But that's your business. :)
>>
>> --
>> Laurent
>>
>>
>
Received on Fri Mar 04 2016 - 22:15:59 UTC