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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 (
"runtime"
"syscall"
)
// Process stores the information about a process created by StartProcess.
type Process struct {
Pid int
handle int
}
func newProcess(pid, handle int) *Process {
p := &Process{pid, handle}
runtime.SetFinalizer(p, (*Process).Release)
return p
}
// 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.
Files []*File
}
// StartProcess starts a new process with the program, arguments and attributes
// specified by name, argv and attr.
func StartProcess(name string, argv []string, attr *ProcAttr) (p *Process, err Error) {
sysattr := &syscall.ProcAttr{
Dir: attr.Dir,
Env: attr.Env,
}
if sysattr.Env == nil {
sysattr.Env = Environ()
}
// Create array of integer (system) fds.
intfd := make([]int, len(attr.Files))
for i, f := range attr.Files {
if f == nil {
intfd[i] = -1
} else {
intfd[i] = f.Fd()
}
}
sysattr.Files = intfd
pid, h, e := syscall.StartProcess(name, argv, sysattr)
if e != 0 {
return nil, &PathError{"fork/exec", name, Errno(e)}
}
return newProcess(pid, h), nil
}
// Exec replaces the current process with an execution of the
// named binary, with arguments argv and environment envv.
// If successful, Exec never returns. If it fails, it returns an Error.
// StartProcess is almost always a better way to execute a program.
func Exec(name string, argv []string, envv []string) Error {
if envv == nil {
envv = Environ()
}
e := syscall.Exec(name, argv, envv)
if e != 0 {
return &PathError{"exec", name, Errno(e)}
}
return nil
}
// TODO(rsc): Should os implement its own syscall.WaitStatus
// wrapper with the methods, or is exposing the underlying one enough?
//
// TODO(rsc): Certainly need to have Rusage struct,
// since syscall one might have different field types across
// different OS.
// Waitmsg stores the information about an exited process as reported by Wait.
type Waitmsg struct {
Pid int // The process's id.
syscall.WaitStatus // System-dependent status info.
Rusage *syscall.Rusage // System-dependent resource usage info.
}
// Wait waits for process pid to exit or stop, and then returns a
// Waitmsg describing its status and an Error, if any. The options
// (WNOHANG etc.) affect the behavior of the Wait call.
// Wait is equivalent to calling FindProcess and then Wait
// and Release on the result.
func Wait(pid int, options int) (w *Waitmsg, err Error) {
p, e := FindProcess(pid)
if e != nil {
return nil, e
}
defer p.Release()
return p.Wait(options)
}
// Convert i to decimal string.
func itod(i int) string {
if i == 0 {
return "0"
}
u := uint64(i)
if i < 0 {
u = -u
}
// Assemble decimal in reverse order.
var b [32]byte
bp := len(b)
for ; u > 0; u /= 10 {
bp--
b[bp] = byte(u%10) + '0'
}
if i < 0 {
bp--
b[bp] = '-'
}
return string(b[bp:])
}
func (w Waitmsg) String() string {
// TODO(austin) Use signal names when possible?
res := ""
switch {
case w.Exited():
res = "exit status " + itod(w.ExitStatus())
case w.Signaled():
res = "signal " + itod(w.Signal())
case w.Stopped():
res = "stop signal " + itod(w.StopSignal())
if w.StopSignal() == syscall.SIGTRAP && w.TrapCause() != 0 {
res += " (trap " + itod(w.TrapCause()) + ")"
}
case w.Continued():
res = "continued"
}
if w.CoreDump() {
res += " (core dumped)"
}
return res
}
// 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() }
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