main.go

package main

import (
	"fmt"
	"io/ioutil"
	"os/exec"
)

/*
Sometimes our Go programs need to spawn other, non-Go processes.
For example, the syntax highlighting on this site is implemented
by spawning a pygmentize process from a Go program.
Let’s look at a few examples of spawning processes from Go.
*/

// Process function to illustrate how to launch process in go.
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")

	// .Output is another helper that handles the common case of
	// running a command, waiting for it to finish, and collecting
	// its 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))

	// 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, _ := ioutil.ReadAll(grepOut)
	grepCmd.Wait()
	fmt.Println("> grep hello")
	fmt.Println(string(grepBytes))

	// Note that when spawning commands we need to provide an
	// explicitly delineated command and argument array,
	// vs. being able to just pass in one command-line string.
	// If you want to spawn a full command with a string,
	// you can use bash’s -c option:
	lsCmd := exec.Command("bash", "-c", "kubectl get nodes")
	lsOut, err := lsCmd.Output()
	if err != nil {
		panic(err)
	}
	fmt.Println("> kubectl get nodes")
	fmt.Println(string(lsOut))
}