process: signals, liveness, exec¶

import "github.com/grokify/oscompat/process"

Stopping a process¶

Windows has no SIGTERM.

err := process.Signal(pid)         // SIGTERM on Unix, Kill on Windows
err = process.FindAndSignal(pid)   // finds the process first

Detached children¶

cmd := exec.Command("myapp", "serve")
process.SetDetached(cmd) // its own process group on Unix
err := cmd.Start()

Is it still the same process?¶

A file that records a PID goes stale when the process dies, and the system can give the same PID to an unrelated process. Compare the start time.

ok, err := process.Exists(rec.PID)

started, err := process.StartTime(rec.PID)
switch {
case errors.Is(err, process.ErrNotFound):
    // gone
case err == nil && started.Sub(rec.StartedAt).Abs() > 2*time.Second:
    // the PID was reused by a different process
}

Function	Behavior
`Exists(pid)`	Whether the process is running. A process owned by another user counts as running
`StartTime(pid)`	The start time, or `ErrNotFound`

On Unix the start time comes from ps and has one-second resolution, so allow a tolerance when comparing. On Windows it is the creation time. A PID of zero or less is rejected, because on Unix it addresses a process group.

Replacing the current process¶

err := process.Exec(path, []string{"claude", "--resume", id})

Unix replaces the process. Windows cannot, so it runs the program as a child with the terminal attached and exits with its status. It returns only on failure.