lean into examples

examples/execing-processes/execing-processes.go

@@ -0,0 +1,41 @@
+// In the previous example we looked at spawning external
+// process. We do this when we need the functionality
+// of another process accessable to a running Go process.
+// In other cases we may just want to completely replace
+// the current Go process with another process. To do
+// this we'll use Go's implementation of the `exec`.
+
+// In this example we'll exec an `ls` command.
+package main
+
+import "syscall"
+import "os"
+import "os/exec"
+
+func main() {
+    // We'll need an absolute path to the binary we'd
+    // like to execute. In this case we'll get the path
+    // for `ls`, 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). Here we'll give `ls`
+    // a few arguments
+    args := []string{"-a", "-l", "-h"}
+
+    // We'll give the command we execute our current
+    // environment.
+    env := os.Environ()
+
+    // The actual exec call. If this call is succesful,
+    // the execution of our process will end here and it
+    // will 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)
+    }
+}

examples/execing-processes/execing-processes.sh

@@ -0,0 +1,14 @@
+# Now if we run this we'll see our programm replaced
+# by `ls`.
+
+$ go run execing-processes.go
+$ ls -a -l -h
+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 execing
+# processes covers most use cases for `fork`.