Add shell command to capture and stream output

shell/cmd.go

@@ -5,6 +5,8 @@ import (
 	"os"
 	"strings"
 	"github.com/gruntwork-io/gruntwork-cli/errors"
+	"io"
+	"bufio"
 )
 
 // Run the specified shell command with the specified arguments. Connect the command's stdin, stdout, and stderr to
@@ -37,6 +39,72 @@ func RunShellCommandAndGetOutput(options *ShellOptions, command string, args ...
 	return string(out), errors.WithStackTrace(err)
 }
 
+// Run the specified shell command with the specified arguments. Return its stdout and stderr as a string and also
+// stream stdout and stderr to the OS stdout/stderr
+func RunShellCommandAndGetAndStreamOutput(options *ShellOptions, command string, args ... string) (string, error) {
+	options.Logger.Infof("Running command: %s %s", command, strings.Join(args, " "))
+
+	cmd := exec.Command(command, args...)
+
+	cmd.Dir = options.WorkingDir
+
+	cmd.Stdin = os.Stdin
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return "", errors.WithStackTrace(err)
+	}
+
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return "", errors.WithStackTrace(err)
+	}
+
+	if err := cmd.Start(); err != nil {
+		return "", errors.WithStackTrace(err)
+	}
+
+	output, err := readStdoutAndStderr(stdout, stderr, options)
+	if err != nil {
+		return output, err
+	}
+
+	err = cmd.Wait()
+	return output, errors.WithStackTrace(err)
+}
+
+// This function captures stdout and stderr while still printing it to the stdout and stderr of this Go program
+func readStdoutAndStderr(stdout io.ReadCloser, stderr io.ReadCloser, options *ShellOptions) (string, error) {
+	allOutput := []string{}
+
+	stdoutScanner := bufio.NewScanner(stdout)
+	stderrScanner := bufio.NewScanner(stderr)
+
+	for {
+		if stdoutScanner.Scan() {
+			text := stdoutScanner.Text()
+			options.Logger.Println(text)
+			allOutput = append(allOutput, text)
+		} else if stderrScanner.Scan() {
+			text := stderrScanner.Text()
+			options.Logger.Println(text)
+			allOutput = append(allOutput, text)
+		} else {
+			break
+		}
+	}
+
+	if err := stdoutScanner.Err(); err != nil {
+		return "", errors.WithStackTrace(err)
+	}
+
+	if err := stderrScanner.Err(); err != nil {
+		return "", errors.WithStackTrace(err)
+	}
+
+	return strings.Join(allOutput, "\n"), nil
+}
+
 // Return true if the OS has the given command installed
 func CommandInstalled(command string) bool {
 	_, err := exec.LookPath(command)