Matomo: [Docs] Explain shell_exec requirement

[Findus23]

I am a bit confused by the usage of shell_exec in Matomo and can't find any docs for it.

• https://matomo.org/docs/requirements/ doesn't mention that it is required
• In the few places I checked there is often a if (!function_exists('shell_exec')) { indicating that is only recommended, but not required
• There are no docs explaining what Matomo needs shell_exec for (or even what it is and how to enable it)
  
  
  
  • Therefore there are many recurring questions about it on the forum like https://forum.matomo.org/t/shell-exec-sie-mussen-diese-eingebaute-funktion-aktivieren/23079/2
  
  
• The system check is called RecommendedFunctionsCheck indicating that it isn't required
• but the warning it gives is You need to enable this built-in function. and Sie müssen diese eingebaute Funktion aktivieren indicating that it is required.

Can someone who knows the background help clarifying all docs?

[whalehub]

@mattab I see that addressing this topic is planned for the 4.x series of releases, but in the meantime, do you mind answering the question of whether or not enabling shell_exec is mandatory for using the 3.x series of Matomo releases?

[tsteur]

I had a very quick look and doesn't seem to be required, only optional.