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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package os
import (
// ErrProcessDone indicates a Process has finished.
var ErrProcessDone = errors.New("os: process already finished")
// Process stores the information about a process created by StartProcess.
type Process struct {
Pid int
handle uintptr // handle is accessed atomically on Windows
isdone uint32 // process has been successfully waited on, non zero if true
sigMu sync.RWMutex // avoid race between wait and signal
func newProcess(pid int, handle uintptr) *Process {
p := &Process{Pid: pid, handle: handle}
runtime.SetFinalizer(p, (*Process).Release)
return p
func (p *Process) setDone() {
atomic.StoreUint32(&p.isdone, 1)
func (p *Process) done() bool {
return atomic.LoadUint32(&p.isdone) > 0
// ProcAttr holds the attributes that will be applied to a new process
// started by StartProcess.
type ProcAttr struct {
// If Dir is non-empty, the child changes into the directory before
// creating the process.
Dir string
// If Env is non-nil, it gives the environment variables for the
// new process in the form returned by Environ.
// If it is nil, the result of Environ will be used.
Env []string
// Files specifies the open files inherited by the new process. The
// first three entries correspond to standard input, standard output, and
// standard error. An implementation may support additional entries,
// depending on the underlying operating system. A nil entry corresponds
// to that file being closed when the process starts.
// On Unix systems, StartProcess will change these File values
// to blocking mode, which means that SetDeadline will stop working
// and calling Close will not interrupt a Read or Write.
Files []*File
// Operating system-specific process creation attributes.
// Note that setting this field means that your program
// may not execute properly or even compile on some
// operating systems.
Sys *syscall.SysProcAttr
// A Signal represents an operating system signal.
// The usual underlying implementation is operating system-dependent:
// on Unix it is syscall.Signal.
type Signal interface {
String() string
Signal() // to distinguish from other Stringers
// Getpid returns the process id of the caller.
func Getpid() int { return syscall.Getpid() }
// Getppid returns the process id of the caller's parent.
func Getppid() int { return syscall.Getppid() }
// FindProcess looks for a running process by its pid.
// The Process it returns can be used to obtain information
// about the underlying operating system process.
// On Unix systems, FindProcess always succeeds and returns a Process
// for the given pid, regardless of whether the process exists.
func FindProcess(pid int) (*Process, error) {
return findProcess(pid)
// StartProcess starts a new process with the program, arguments and attributes
// specified by name, argv and attr. The argv slice will become os.Args in the
// new process, so it normally starts with the program name.
// If the calling goroutine has locked the operating system thread
// with runtime.LockOSThread and modified any inheritable OS-level
// thread state (for example, Linux or Plan 9 name spaces), the new
// process will inherit the caller's thread state.
// StartProcess is a low-level interface. The os/exec package provides
// higher-level interfaces.
// If there is an error, it will be of type *PathError.
func StartProcess(name string, argv []string, attr *ProcAttr) (*Process, error) {
return startProcess(name, argv, attr)
// Release releases any resources associated with the Process p,
// rendering it unusable in the future.
// Release only needs to be called if Wait is not.
func (p *Process) Release() error {
return p.release()
// Kill causes the Process to exit immediately. Kill does not wait until
// the Process has actually exited. This only kills the Process itself,
// not any other processes it may have started.
func (p *Process) Kill() error {
return p.kill()
// Wait waits for the Process to exit, and then returns a
// ProcessState describing its status and an error, if any.
// Wait releases any resources associated with the Process.
// On most operating systems, the Process must be a child
// of the current process or an error will be returned.
func (p *Process) Wait() (*ProcessState, error) {
return p.wait()
// Signal sends a signal to the Process.
// Sending Interrupt on Windows is not implemented.
func (p *Process) Signal(sig Signal) error {
return p.signal(sig)
// UserTime returns the user CPU time of the exited process and its children.
func (p *ProcessState) UserTime() time.Duration {
return p.userTime()
// SystemTime returns the system CPU time of the exited process and its children.
func (p *ProcessState) SystemTime() time.Duration {
return p.systemTime()
// Exited reports whether the program has exited.
func (p *ProcessState) Exited() bool {
return p.exited()
// Success reports whether the program exited successfully,
// such as with exit status 0 on Unix.
func (p *ProcessState) Success() bool {
return p.success()
// Sys returns system-dependent exit information about
// the process. Convert it to the appropriate underlying
// type, such as syscall.WaitStatus on Unix, to access its contents.
func (p *ProcessState) Sys() interface{} {
return p.sys()
// SysUsage returns system-dependent resource usage information about
// the exited process. Convert it to the appropriate underlying
// type, such as *syscall.Rusage on Unix, to access its contents.
// (On Unix, *syscall.Rusage matches struct rusage as defined in the
// getrusage(2) manual page.)
func (p *ProcessState) SysUsage() interface{} {
return p.sysUsage()