Go by Example: Exec'ing Processes

In the previous example we looked at spawning external 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 `exec` function.
	package main
	import "syscall" import "os" import "os/exec"
	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 to use. Here we just provide our current environment.	env := os.Environ()
Here’s the actual `os.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) } }

When we run our program it is replaced by `ls`.	$ go run execing-processes.go total 16 drwxr-xr-x 4 mark 136B Oct 3 16:29 . drwxr-xr-x 91 mark 3.0K Oct 3 12:50 .. -rw-r--r-- 1 mark 1.3K Oct 3 16:28 execing-processes.go
Note that Go does not offer a classic Unix `fork` function. Usually this isn’t an issue though, since starting goroutines, spawning processes, and exec’ing processes covers most use cases for `fork`.

Previous example: Spawning Processes.

Next example: Signals.