Re: Feature requests for execline & s6

From: Laurent Bercot <>
Date: Tue, 27 Jan 2015 00:12:22 +0100

On 26/01/2015 23:52, Olivier Brunel wrote:
> That looks good, except that I need a default value, in case the file
> doesn't exist. If there's a way to work a default value in that case
> then that'd be fine, yes.
> there a way to add a default value if FILE doesn't exist?

  I will add a "-D default" option to backtick, for when the subprocess
exits nonzero. I've wanted this feature for some time, but only now
realized that I wanted it. Thanks for helping me clarify my mind. :)

> (re: misconfiguration, in what way though? It could lead to the program
> being triggered for each new line, but that doesn't mean uncontrollably
> spawning children?

  Well, some services log a lot. Spawning a process for every new line
can be really, really heavy. (And I don't even want to imagine how heavy
it would be on Solaris.)
  I really don't mind forking and execing, as can be proven by execline;
but potentially forking every time a daemon outputs a newline is still
really scary. I need to find the right safety guards before I implement

> It might be a lot, but with a rotation every 4096 bytes one might
> already have frequent calls to the processor, no?)

  Sure, with s4096, but who limits their log files to 4k ? It requires
specific configuration to do that; the admin really wanted it to
happen, it's controlled. A daemon's output matching a given regexp
- which could be .* - is a lot less predictable. And if the daemon is
spewing nothing but newlines, you could find yourself forking 4096 times
more than you're already doing with the processor...

Received on Mon Jan 26 2015 - 23:12:22 UTC

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