Function agent_running 

pub fn agent_running(pid: u32) -> bool

Check whether a process with the given PID is still running.

The PID typically comes from parsing an on-disk file, so hostile or corrupted values must be rejected, not reinterpreted: kill(0, sig) signals the caller’s own process group (a “0” PID file would read as permanently alive), and a value above i32::MAX would wrap negative through an as libc::pid_t cast — kill(-1, 0) probes every process the caller may signal and virtually always succeeds.