Function main

examples/spawning-processes/spawning-processes.go:13–87

()

)

func main() {

	// We'll start with a simple command that takes no
	// arguments or input and just prints something to
	// stdout. The `exec.Command` helper creates an object
	// to represent this external process.
	dateCmd := exec.Command("date")

	// The `Output` method runs the command, waits for it
	// to finish and collects its standard output.
	//  If there were no errors, `dateOut` will hold bytes
	// with the date info.
	dateOut, err := dateCmd.Output()
	if err != nil {
		panic(err)
	}
	fmt.Println("> date")
	fmt.Println(string(dateOut))

	// `Output` and other methods of `Command` will return
	// `*exec.Error` if there was a problem executing the
	// command (e.g. wrong path), and `*exec.ExitError`
	// if the command ran but exited with a non-zero return
	// code.
	_, err = exec.Command("date", "-x").Output()
	if err != nil {
		if e, ok := errors.AsType[*exec.Error](err); ok {
			fmt.Println("failed executing:", e)
		} else if e, ok := errors.AsType[*exec.ExitError](err); ok {
			exitCode := e.ExitCode()
			fmt.Println("command exit rc =", exitCode)
		} else {
			panic(err)
		}
	}

	// Next we'll look at a slightly more involved case
	// where we pipe data to the external process on its
	// `stdin` and collect the results from its `stdout`.
	grepCmd := exec.Command("grep", "hello")

	// Here we explicitly grab input/output pipes, start
	// the process, write some input to it, read the
	// resulting output, and finally wait for the process
	// to exit.
	grepIn, _ := grepCmd.StdinPipe()
	grepOut, _ := grepCmd.StdoutPipe()
	grepCmd.Start()
	grepIn.Write([]byte("hello grep\ngoodbye grep"))
	grepIn.Close()
	grepBytes, _ := io.ReadAll(grepOut)
	grepCmd.Wait()

	// We omitted error checks in the above example, but
	// you could use the usual `if err != nil` pattern for
	// all of them. We also only collect the `StdoutPipe`
	// results, but you could collect the `StderrPipe` in
	// exactly the same way.