5 ms·

Why is it even possible to represent a negative PID, let alone treat the integer -1 as a PID meaning "all effective processes"? This seems like a mistake (if no

Why is it even possible to represent a negative PID, let alone treat the integer -1 as a PID meaning "all effective processes"? This seems like a mistake (if not a rookie mistake) in the Linux kernel API itself.

antonvs 6mo ago
Pretty much all the rough edges being discussed here are design mistakes in Linux or Unix, and/or a consequence of using an unsafe language with limited abstractions and a weak type system. But because of ubiquity, this is everyone’s problem now.
- adrian_b 6mo ago
  You are right, but those who set for themselves the goal to substitute a Linux/UNIX package must implement programs that handle correctly all the quirks of the existing Linux/POSIX specifications. If they do not like the design mistakes, great, they should set for themselves the goal to write a new operating system together with all base applications, where all these mistakes are corrected. As long as they have not chosen the second goal, but the first, they are constrained by the existing interfaces and they must use them correctly, no matter how inconvenient that may be. Anyone who learns English may be frustrated by many design mistakes of English, but they must still use English as it is spoken by the natives, otherwise they will not be understood.
nine_k 6mo ago
-1 is a special case, a way to represent a PID with all bits set in a platform-independent way. It's not very clean, and it comes from ancient times when writing some extra code and storing an extra few bytes was way more expensive.
- bonzini 6mo ago
  No, -1 is simply the process group with pgid 1: https://stackoverflow.com/questions/392022/whats-the-best-way-to-send-a-signal-to-all-members-of-a-process-group https://stackoverflow.com/questions/392022/whats-the-best-wa... The problem is that -DIGIT doubles as both "signal number" and process group. The right way to invoke kill for a process group however would be "kill [OPTS]... -- -PGID".
dminik 6mo ago
It feels a bit like a "better is better" language hitting all of the quirks of a "worse is better" environment.

antonvs 6mo ago

Pretty much all the rough edges being discussed here are design mistakes in Linux or Unix, and/or a consequence of using an unsafe language with limited abstractions and a weak type system. But because of ubiquity, this is everyone’s problem now.

adrian_b 6mo ago
You are right, but those who set for themselves the goal to substitute a Linux/UNIX package must implement programs that handle correctly all the quirks of the existing Linux/POSIX specifications. If they do not like the design mistakes, great, they should set for themselves the goal to write a new operating system together with all base applications, where all these mistakes are corrected. As long as they have not chosen the second goal, but the first, they are constrained by the existing interfaces and they must use them correctly, no matter how inconvenient that may be. Anyone who learns English may be frustrated by many design mistakes of English, but they must still use English as it is spoken by the natives, otherwise they will not be understood.

nine_k 6mo ago

-1 is a special case, a way to represent a PID with all bits set in a platform-independent way. It's not very clean, and it comes from ancient times when writing some extra code and storing an extra few bytes was way more expensive.

bonzini 6mo ago
No, -1 is simply the process group with pgid 1: https://stackoverflow.com/questions/392022/whats-the-best-way-to-send-a-signal-to-all-members-of-a-process-group https://stackoverflow.com/questions/392022/whats-the-best-wa... The problem is that -DIGIT doubles as both "signal number" and process group. The right way to invoke kill for a process group however would be "kill [OPTS]... -- -PGID".

dminik 6mo ago

It feels a bit like a "better is better" language hitting all of the quirks of a "worse is better" environment.