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Go

// In the previous example we looked at
// [spawning external processes](spawning-processes). We
// do this 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
// <a href="http://en.wikipedia.org/wiki/Exec_(operating_system)"><code>exec</code></a>
// function.
package main
import (
"os"
"os/exec"
"syscall"
)
func main() {
// 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 (probably
// `/bin/ls`).
binary, lookErr := exec.LookPath("ls")
if lookErr != nil {
panic(lookErr)
}
// `Exec` requires arguments in slice form (as
// apposed to one big string). We'll give `ls` a few
// common arguments. Note that the first argument should
// be the program name.
args := []string{"ls", "-a", "-l", "-h"}
// `Exec` also needs a set of [environment variables](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 `/bin/ls -a -l -h`
// process. If there is an error we'll get a return
// value.
execErr := syscall.Exec(binary, args, env)
if execErr != nil {
panic(execErr)
}
}