exec

type Cmd struct {
	// Path is the path of the command to run.
	//
	// This is the only field that must be set to a non-zero
	// value. If Path is relative, it is evaluated relative
	// to Dir.
	Path string

	// Args holds command line arguments, including the command as Args[0].
	// If the Args field is empty or nil, Run uses {Path}.
	//
	// In typical use, both Path and Args are set by calling Command.
	Args []string

	// Env specifies the environment of the process.
	// Each entry is of the form "key=value".
	// If Env is nil, the new process uses the current process's
	// environment.
	// If Env contains duplicate environment keys, only the last
	// value in the slice for each duplicate key is used.
	// As a special case on Windows, SYSTEMROOT is always added if
	// missing and not explicitly set to the empty string.
	Env []string

	// Dir specifies the working directory of the command.
	// If Dir is the empty string, Run runs the command in the
	// calling process's current directory.
	Dir string

	// Stdin specifies the process's standard input.
	//
	// If Stdin is nil, the process reads from the null device (os.DevNull).
	//
	// If Stdin is an *os.File, the process's standard input is connected
	// directly to that file.
	//
	// Otherwise, during the execution of the command a separate
	// goroutine reads from Stdin and delivers that data to the command
	// over a pipe. In this case, Wait does not complete until the goroutine
	// stops copying, either because it has reached the end of Stdin
	// (EOF or a read error), or because writing to the pipe returned an error,
	// or because a nonzero WaitDelay was set and expired.
	Stdin io.Reader

	// Stdout and Stderr specify the process's standard output and error.
	//
	// If either is nil, Run connects the corresponding file descriptor
	// to the null device (os.DevNull).
	//
	// If either is an *os.File, the corresponding output from the process
	// is connected directly to that file.
	//
	// Otherwise, during the execution of the command a separate goroutine
	// reads from the process over a pipe and delivers that data to the
	// corresponding Writer. In this case, Wait does not complete until the
	// goroutine reaches EOF or encounters an error or a nonzero WaitDelay
	// expires.
	//
	// If Stdout and Stderr are the same writer, and have a type that can
	// be compared with ==, at most one goroutine at a time will call Write.
	Stdout io.Writer
	Stderr io.Writer

	// ExtraFiles specifies additional open files to be inherited by the
	// new process. It does not include standard input, standard output, or
	// standard error. If non-nil, entry i becomes file descriptor 3+i.
	//
	// ExtraFiles is not supported on Windows.
	ExtraFiles []*os.File

	// SysProcAttr holds optional, operating system-specific attributes.
	// Run passes it to os.StartProcess as the os.ProcAttr's Sys field.
	SysProcAttr *syscall.SysProcAttr

	// Process is the underlying process, once started.
	Process *os.Process

	// ProcessState contains information about an exited process.
	// If the process was started successfully, Wait or Run will
	// populate its ProcessState when the command completes.
	ProcessState *os.ProcessState

	Err error // LookPath error, if any.

	// If Cancel is non-nil, the command must have been created with
	// CommandContext and Cancel will be called when the command's
	// Context is done. By default, CommandContext sets Cancel to
	// call the Kill method on the command's Process.
	//
	// Typically a custom Cancel will send a signal to the command's
	// Process, but it may instead take other actions to initiate cancellation,
	// such as closing a stdin or stdout pipe or sending a shutdown request on a
	// network socket.
	//
	// If the command exits with a success status after Cancel is
	// called, and Cancel does not return an error equivalent to
	// os.ErrProcessDone, then Wait and similar methods will return a non-nil
	// error: either an error wrapping the one returned by Cancel,
	// or the error from the Context.
	// (If the command exits with a non-success status, or Cancel
	// returns an error that wraps os.ErrProcessDone, Wait and similar methods
	// continue to return the command's usual exit status.)
	//
	// If Cancel is set to nil, nothing will happen immediately when the command's
	// Context is done, but a nonzero WaitDelay will still take effect. That may
	// be useful, for example, to work around deadlocks in commands that do not
	// support shutdown signals but are expected to always finish quickly.
	//
	// Cancel will not be called if Start returns a non-nil error.
	Cancel func() error

	// If WaitDelay is non-zero, it bounds the time spent waiting on two sources
	// of unexpected delay in Wait: a child process that fails to exit after the
	// associated Context is canceled, and a child process that exits but leaves
	// its I/O pipes unclosed.
	//
	// The WaitDelay timer starts when either the associated Context is done or a
	// call to Wait observes that the child process has exited, whichever occurs
	// first. When the delay has elapsed, the command shuts down the child process
	// and/or its I/O pipes.
	//
	// If the child process has failed to exit — perhaps because it ignored or
	// failed to receive a shutdown signal from a Cancel function, or because no
	// Cancel function was set — then it will be terminated using os.Process.Kill.
	//
	// Then, if the I/O pipes communicating with the child process are still open,
	// those pipes are closed in order to unblock any goroutines currently blocked
	// on Read or Write calls.
	//
	// If pipes are closed due to WaitDelay, no Cancel call has occurred,
	// and the command has otherwise exited with a successful status, Wait and
	// similar methods will return ErrWaitDelay instead of nil.
	//
	// If WaitDelay is zero (the default), I/O pipes will be read until EOF,
	// which might not occur until orphaned subprocesses of the command have
	// also closed their descriptors for the pipes.
	WaitDelay time.Duration
	// contains filtered or unexported fields
}