dotcloud/docker

//go:build !windows

package process

import (
    "bytes"
    "fmt"
    "os"
    "path/filepath"
    "runtime"
    "strconv"

    "golang.org/x/sys/unix"
)

// Alive returns true if process with a given pid is running. It only considers
// positive PIDs; 0 (all processes in the current process group), -1 (all processes
// with a PID larger than 1), and negative (-n, all processes in process group
// "n") values for pid are never considered to be alive.
func Alive(pid int) bool {
    if pid < 1 {
        return false
    }
    switch runtime.GOOS {
    case "darwin":
        // OS X does not have a proc filesystem. Use kill -0 pid to judge if the
        // process exists. From KILL(2): https://www.freebsd.org/cgi/man.cgi?query=kill&sektion=2&manpath=OpenDarwin+7.2.1
        //
        // Sig may be one of the signals specified in sigaction(2) or it may
        // be 0, in which case error checking is performed but no signal is
        // actually sent. This can be used to check the validity of pid.
        err := unix.Kill(pid, 0)

        // Either the PID was found (no error) or we get an EPERM, which means
        // the PID exists, but we don't have permissions to signal it.
        return err == nil || err == unix.EPERM
    default:
        _, err := os.Stat(filepath.Join("/proc", strconv.Itoa(pid)))
        return err == nil
    }
}

// Kill force-stops a process. It only considers positive PIDs; 0 (all processes
// in the current process group), -1 (all processes with a PID larger than 1),
// and negative (-n, all processes in process group "n") values for pid are
// ignored. Refer to [KILL(2)] for details.
//
// [KILL(2)]: https://man7.org/linux/man-pages/man2/kill.2.html
func Kill(pid int) error {
    if pid < 1 {
        return fmt.Errorf("invalid PID (%d): only positive PIDs are allowed", pid)
    }
    err := unix.Kill(pid, unix.SIGKILL)
    if err != nil && err != unix.ESRCH {
        return err
    }
    return nil
}

// Zombie return true if process has a state with "Z". It only considers positive
// PIDs; 0 (all processes in the current process group), -1 (all processes with
// a PID larger than 1), and negative (-n, all processes in process group "n")
// values for pid are ignored. Refer to [PROC(5)] for details.
//
// [PROC(5)]: https://man7.org/linux/man-pages/man5/proc.5.html
func Zombie(pid int) (bool, error) {
    if pid < 1 {
        return false, nil
    }
    data, err := os.ReadFile(fmt.Sprintf("/proc/%d/stat", pid))
    if err != nil {
        if os.IsNotExist(err) {
            return false, nil
        }
        return false, err
    }
    if cols := bytes.SplitN(data, []byte(" "), 4); len(cols) >= 3 && string(cols[2]) == "Z" {
        return true, nil
    }
    return false, nil
}