Executing Commands

Timing Out with Interrupt and then Kill

c := exec.Command(name, arg...)
b := &bytes.Buffer{}
c.Stdout = b
c.Stdin = stdin
if err := c.Start(); err != nil {
    return nil, err
}
timedOut := false
intTimer := time.AfterFunc(timeout, func() {
    log.Printf("Process taking too long. Interrupting: %s %s", name, strings.Join(arg, " "))
    c.Process.Signal(os.Interrupt)
    timedOut = true
})
killTimer := time.AfterFunc(timeout*2, func() {
    log.Printf("Process taking too long. Killing: %s %s", name, strings.Join(arg, " "))
    c.Process.Signal(os.Kill)
    timedOut = true
})
err := c.Wait()
intTimer.Stop()
killTimer.Stop()
if timedOut {
    log.Print("the process timed out\n")
}

Simple Command Execution

// Execute a command a capture standard out. exec.Command creates the command
// and then the chained Output method gets standard out. Use CombinedOutput() 
// if you want both standard out and standerr output
out, err := exec.Command("echo", "foo").Output()
if err != nil {
    log.Fatal(err)
}

Executing a Command then Continue and Wait

cmd := exec.Command("sleep", "5")

// Does not wait for command to complete before returning
err := cmd.Start()
if err != nil {
    log.Fatal(err)
}

// Wait for cmd to Return
err = cmd.Wait()
log.Printf("Command finished with error: %v", err)

Running a Command twice

A Cmd cannot be reused after calling its Run, Output or CombinedOutput methods

Running a command twice will not work:

cmd := exec.Command("xte", "key XF86AudioPlay")
_ := cmd.Run() // Play audio key press
// .. do something else
err := cmd.Run() // Pause audio key press, fails

Error: exec: already started

Rather, one must use two separate exec.Command. You might also need some delay between commands.

cmd := exec.Command("xte", "key XF86AudioPlay")
_ := cmd.Run() // Play audio key press
// .. wait a moment
cmd := exec.Command("xte", "key XF86AudioPlay")
_ := cmd.Run() // Pause audio key press