1import os
 2
 3from plain.runtime import PLAIN_TEMP_PATH
 4
 5
 6class DevPid:
 7    """Manage a pidfile for the running ``plain dev`` command."""
 8
 9    def __init__(self):
10        self.pidfile = PLAIN_TEMP_PATH / "dev" / "dev.pid"
11
12    def write(self):
13        pid = os.getpid()
14        self.pidfile.parent.mkdir(parents=True, exist_ok=True)
15        with self.pidfile.open("w+") as f:
16            f.write(str(pid))
17
18    def rm(self):
19        if self.pidfile.exists():
20            self.pidfile.unlink()
21
22    def exists(self):
23        if not self.pidfile.exists():
24            return False
25        try:
26            pid = int(self.pidfile.read_text())
27        except (ValueError, OSError):
28            self.rm()
29            return False
30        try:
31            os.kill(pid, 0)
32        except OSError:
33            # Stale pidfile
34            self.rm()
35            return False
36        return True