63_execing_processes.go

package gobyexample

import (
	"os"
	"os/exec"
	"syscall"
)

// ExecingProcessesDemo - in the previous example we looked at spawning external processes.
// We do that when we need an external process accessible to a running Go process. Sometimes
// we just want to completely replace the current Go process with another (perhaps non-Go) one.
// To do this we'll use Go's implementation of the classic `exec` function.
func ExecingProcessesDemo() {
	// For our example we'll `exec ls`. Go requires an absolute path to the binary we want to
	// execute, so we'll use `exec.LookPath` to find it.
	binary, lookErr := exec.LookPath("ls")
	if lookErr != nil {
		panic(lookErr)
	}

	// `Exec` requiers arguments in slice form, as opposed to one big string. Note that the first
	// argument should be the program name.
	args := []string{"ls", "-a", "-l", "-h"}

	// `Exec` also needs a set of environment variables to use. Here we just provide our current
	// environment.
	env := os.Environ()

	// Here's the actual `syscall.Exec` call. If this call is successful, the execution of our
	// process will end here and be replaced by the process we defined. If there is an error
	// we'll get a return value.
	execErr := syscall.Exec(binary, args, env)
	if execErr != nil {
		panic(execErr)
	}
}