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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 (
"syscall"
)
// ForkExec forks the current process and invokes Exec with the program, arguments,
// and environment specified by name, argv, and envv. It returns the process
// id of the forked process and an Error, if any. The fd array specifies the
// file descriptors to be set up in the new process: fd[0] will be Unix file
// descriptor 0 (standard input), fd[1] descriptor 1, and so on. A nil entry
// will cause the child to have no open file descriptor with that index.
// If dir is not empty, the child chdirs into the directory before execing the program.
func ForkExec(name string, argv []string, envv []string, dir string, fd []*File) (pid int, err Error) {
if envv == nil {
envv = Environ()
}
// Create array of integer (system) fds.
intfd := make([]int, len(fd))
for i, f := range fd {
if f == nil {
intfd[i] = -1
} else {
intfd[i] = f.Fd()
}
}
p, e := syscall.ForkExec(name, argv, envv, dir, intfd)
if e != 0 {
return 0, &PathError{"fork/exec", name, Errno(e)}
}
return p, 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.
// ForkExec 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.
}
// Options for Wait.
const (
WNOHANG = syscall.WNOHANG // Don't wait if no process has exited.
WSTOPPED = syscall.WSTOPPED // If set, status of stopped subprocesses is also reported.
WUNTRACED = WSTOPPED
WRUSAGE = 1 << 20 // Record resource usage.
)
// WRUSAGE must not be too high a bit, to avoid clashing with Linux's
// WCLONE, WALL, and WNOTHREAD flags, which sit in the top few bits of
// the options
// 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.
func Wait(pid int, options int) (w *Waitmsg, err Error) {
var status syscall.WaitStatus
var rusage *syscall.Rusage
if options&WRUSAGE != 0 {
rusage = new(syscall.Rusage)
options ^= WRUSAGE
}
pid1, e := syscall.Wait4(pid, &status, options, rusage)
if e != 0 {
return nil, NewSyscallError("wait", e)
}
w = new(Waitmsg)
w.Pid = pid1
w.WaitStatus = status
w.Rusage = rusage
return w, nil
}
// 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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