feat: ability to specify runtime OSs where shell-local should run

common/shell-local/config.go

@@ -29,6 +29,9 @@ type Config struct {
 	// The shebang value used when running inline scripts.
 	InlineShebang string `mapstructure:"inline_shebang"`
 
+	// An array of multiple Runtime OSs to run on.
+	OnlyOn []string
+
 	// The file extension to use for the file generated from the inline commands
 	TempfileExtension string `mapstructure:"tempfile_extension"`
 

common/shell-local/run.go

@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"runtime"
 	"sort"
 	"strings"
 
@@ -58,6 +59,20 @@ func Run(ui packer.Ui, config *Config) (bool, error) {
 		if err != nil {
 			return false, err
 		}
+
+		// Check if command can execute against runtime.
+		runCommand := false
+		if len(config.OnlyOn) > 0 {
+			for _, os := range config.OnlyOn {
+				if os == runtime.GOOS {
+					runCommand = true
+				}
+			}
+		} else {
+			runCommand = true
+		}
+
+		if runCommand {
 			ui.Say(fmt.Sprintf("Running local shell script: %s", script))
 
 			comm := &Communicator{
@@ -69,6 +84,7 @@ func Run(ui packer.Ui, config *Config) (bool, error) {
 			// the other communicators; ultimately, this command is just used for
 			// buffers and for reading the final exit status.
 			flattenedCmd := strings.Join(interpolatedCmds, " ")
+
 			cmd := &packer.RemoteCmd{Command: flattenedCmd}
 			log.Printf("[INFO] (shell-local): starting local command: %s", flattenedCmd)
 			if err := cmd.StartWithUi(comm, ui); err != nil {
@@ -84,6 +100,10 @@ func Run(ui packer.Ui, config *Config) (bool, error) {
 					cmd.ExitStatus,
 					script)
 			}
+		} else {
+			ui.Say(fmt.Sprintf("Skipping local shell script due to runtime OS: %s", script))
+			log.Printf("[INFO] (shell-local): skipping command due to runtime OS not specified.")
+		}
 	}
 
 	return true, nil

website/source/docs/provisioners/shell-local.html.md

@@ -108,6 +108,14 @@ Optional parameters:
     **Important:** If you customize this, be sure to include something like the
     `-e` flag, otherwise individual steps failing won't fail the provisioner.
 
+-  `onlyon` (array of strings) - This is an array of 
+    [runtime operating systems](https://golang.org/doc/install/source#environment)
+    where `shell-local` will only run on. This allows you to run `shell-local` *only* 
+    on specific compatible operating systems. If specified, shell-local will only
+    execute if runtime operating system is in the list; otherwise it will skip the 
+    `shell-local` command. The default behavior is for `shell-local` to run if 
+    `onlyon` is not specified.
+
 -  `use_linux_pathing` (bool) - This is only relevant to windows hosts. If you
    are running Packer in a Windows environment with the Windows Subsystem for
    Linux feature enabled, and would like to invoke a bash script rather than