Implement blackbox in Golang (#250)

* Initial release

pkg/bbutil/runbash.go

@@ -0,0 +1,77 @@
+package bbutil
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+)
+
+// RunBash runs a Bash command.
+func RunBash(command string, args ...string) error {
+	cmd := exec.Command(command, args...)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	err := cmd.Start()
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = cmd.Wait()
+	if err != nil {
+		return fmt.Errorf("RunBash cmd=%q err=%w", command, err)
+	}
+	return nil
+}
+
+// RunBashOutput runs a Bash command, captures output.
+func RunBashOutput(command string, args ...string) (string, error) {
+	cmd := exec.Command(command, args...)
+	cmd.Stdin = os.Stdin
+	cmd.Stderr = os.Stderr
+	out, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("RunBashOutput err=%w", err)
+	}
+	return string(out), err
+}
+
+// RunBashOutputSilent runs a Bash command, captures output, discards stderr.
+func RunBashOutputSilent(command string, args ...string) (string, error) {
+	cmd := exec.Command(command, args...)
+	cmd.Stdin = os.Stdin
+	// Leave cmd.Stderr unmodified and stderr is discarded.
+	out, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("RunBashOutputSilent err=%w", err)
+	}
+	return string(out), err
+}
+
+// RunBashInput runs a Bash command, sends input on stdin.
+func RunBashInput(input string, command string, args ...string) error {
+
+	cmd := exec.Command(command, args...)
+	cmd.Stdin = bytes.NewBuffer([]byte(input))
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	err := cmd.Run()
+	if err != nil {
+		return fmt.Errorf("RunBashInput err=%w", err)
+	}
+	return nil
+}
+
+// RunBashInputOutput runs a Bash command, sends input on stdin.
+func RunBashInputOutput(input []byte, command string, args ...string) ([]byte, error) {
+
+	cmd := exec.Command(command, args...)
+	cmd.Stdin = bytes.NewBuffer(input)
+	cmd.Stderr = os.Stderr
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, fmt.Errorf("RunBashInputOutput err=%w", err)
+	}
+	return out, nil
+}