Github user andrewor14 commented on a diff in the pull request:
https://github.com/apache/spark/pull/3916#discussion_r25300377
--- Diff: launcher/src/main/java/org/apache/spark/launcher/Main.java ---
@@ -0,0 +1,185 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.launcher;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.apache.spark.launcher.CommandBuilderUtils.*;
+
+/**
+ * Command line interface for the Spark launcher. Used internally by Spark
scripts.
+ */
+class Main {
+
+ /**
+ * Usage: Main [class] [class args]
+ * <p/>
+ * This CLI works in two different modes:
+ * <ul>
+ * <li>"spark-submit": if <i>class</i> is
"org.apache.spark.deploy.SparkSubmit", the
+ * {@link SparkLauncher} class is used to launch a Spark
application.</li>
+ * <li>"spark-class": if another class is provided, an internal Spark
class is run.</li>
+ * </ul>
+ *
+ * This class works in tandem with the "bin/spark-class" script on
Unix-like systems, and
+ * "bin/spark-class2.cmd" batch script on Windows to execute the final
command.
+ * <p/>
+ * On Unix-like systems, the output is a list of command arguments,
separated by the NULL
+ * character. On Windows, the output is single command line suitable for
direct execution
+ * form the script.
+ */
+ public static void main(String[] argsArray) throws Exception {
+ checkArgument(argsArray.length > 0, "Not enough arguments: missing
class name.");
+
+ List<String> args = new ArrayList<String>(Arrays.asList(argsArray));
+ String className = args.remove(0);
+
+ boolean printLaunchCommand;
+ AbstractCommandBuilder builder;
+ try {
+ if (className.equals("org.apache.spark.deploy.SparkSubmit")) {
+ builder = new SparkSubmitCommandBuilder(args);
+ } else {
+ builder = new SparkClassCommandBuilder(className, args);
+ }
+ printLaunchCommand =
!isEmpty(System.getenv("SPARK_PRINT_LAUNCH_COMMAND"));
+ } catch (IllegalArgumentException e) {
+ builder = new UsageLauncher();
+ printLaunchCommand = false;
+ }
+
+ Map<String, String> env = new HashMap<String, String>();
+ List<String> cmd = builder.buildCommand(env);
+ if (printLaunchCommand) {
+ System.err.println("Spark Command: " + join(" ", cmd));
+ System.err.println("========================================");
+ }
+
+ if (isWindows()) {
+ System.out.println(prepareForWindows(cmd, env));
+ } else {
+ List<String> bashCmd = prepareForBash(cmd, env);
+ for (String c : bashCmd) {
+ System.out.print(c);
+ System.out.print('\0');
+ }
+ }
+ }
+
+ /**
+ * Prepare a command line for execution from a Windows batch script.
+ *
+ * The method quotes all arguments so that spaces are handled as
expected. Quotes within arguments
+ * are "double quoted" (which is batch for escaping a quote). This page
has more details about
+ * quoting and other batch script fun stuff:
http://ss64.com/nt/syntax-esc.html
+ *
+ * The command is executed using "cmd /c" and formatted in single line,
since that's the
+ * easiest way to consume this from a batch script (see
spark-class2.cmd).
+ */
+ private static String prepareForWindows(List<String> cmd, Map<String,
String> childEnv) {
+ StringBuilder cmdline = new StringBuilder("cmd /c \"");
+ for (Map.Entry<String, String> e : childEnv.entrySet()) {
+ cmdline.append(String.format("set %s=%s", e.getKey(), e.getValue()));
+ cmdline.append(" && ");
+ }
+ for (String arg : cmd) {
+ cmdline.append(quoteForBatchScript(arg));
+ cmdline.append(" ");
+ }
+ cmdline.append("\"");
+ return cmdline.toString();
+ }
+
+ /**
+ * Prepare the command for execution from a bash script. The final
command will have commands to
+ * set up any needed environment variables needed by the child process.
+ */
+ private static List<String> prepareForBash(List<String> cmd, Map<String,
String> childEnv) {
+ if (childEnv.isEmpty()) {
+ return cmd;
+ }
+
+ List<String> newCmd = new ArrayList<String>();
+ newCmd.add("env");
+
+ for (Map.Entry<String, String> e : childEnv.entrySet()) {
+ newCmd.add(String.format("%s=%s", e.getKey(), e.getValue()));
+ }
+ newCmd.addAll(cmd);
+ return newCmd;
+ }
+
+ /**
+ * Quote a command argument for a command to be run by a Windows batch
script, if the argument
+ * needs quoting. Arguments only seem to need quotes in batch scripts if
they have whitespace.
+ */
+ private static String quoteForBatchScript(String arg) {
--- End diff --
also it would be good to have some tests for this. The fact that this is in
`Main.java` makes it a little hard to test. Maybe we should move it to
`CommandBuilderUtils` or something
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