CLI tools: write errors to stderr instead of stdout

Most of our CLI tools use the Terminal class, which previously did not provide methods for writing to standard output. When all output goes to standard out, there are two basic problems. First, errors and warnings are "swallowed" in pipelines, making it hard for a user to know when something's gone wrong. Second, errors and warnings are intermingled with legitimate output, making it difficult to pass the results of interactive scripts to other tools.

This commit adds a second set of print commands to Terminal for printing to standard error, with errorPrint corresponding to print and errorPrintln corresponding to println. This leaves it to developers to decide which output should go where. It also adjusts existing commands to send errors and warnings to stderr.

Usage is printed to standard output when it's correctly requested (e.g., bin/elasticsearch-keystore --help) but goes to standard error when a command is invoked incorrectly (e.g. bin/elasticsearch-keystore list-with-a-typo | sort).

distribution/tools/plugin-cli/src/main/java/org/elasticsearch/plugins/ListPluginsCommand.java

@@ -66,7 +66,7 @@ class ListPluginsCommand extends EnvironmentAwareCommand {
         PluginInfo info = PluginInfo.readFromProperties(env.pluginsFile().resolve(plugin));
         terminal.println(Terminal.Verbosity.VERBOSE, info.toString(prefix));
         if (info.getElasticsearchVersion().equals(Version.CURRENT) == false) {
-            terminal.println("WARNING: plugin [" + info.getName() + "] was built for Elasticsearch version " + info.getVersion() +
+            terminal.errorPrintln("WARNING: plugin [" + info.getName() + "] was built for Elasticsearch version " + info.getVersion() +
                 " but version " + Version.CURRENT + " is required");
         }
     }

distribution/tools/plugin-cli/src/test/java/org/elasticsearch/plugins/InstallPluginCommandTests.java

@@ -789,7 +789,7 @@ public class InstallPluginCommandTests extends ESTestCase {
     public void testBatchFlag() throws Exception {
         MockTerminal terminal = new MockTerminal();
         installPlugin(terminal, true);
-        assertThat(terminal.getOutput(), containsString("WARNING: plugin requires additional permissions"));
+        assertThat(terminal.getErrorOutput(), containsString("WARNING: plugin requires additional permissions"));
         assertThat(terminal.getOutput(), containsString("-> Downloading"));
         // No progress bar in batch mode
         assertThat(terminal.getOutput(), not(containsString("100%")));
@@ -1225,7 +1225,7 @@ public class InstallPluginCommandTests extends ESTestCase {
             UserException e = expectThrows(UserException.class, () -> installPlugin(pluginZip, env.v1()));
             assertEquals("installation aborted by user", e.getMessage());
 
-            assertThat(terminal.getOutput(), containsString("WARNING: " + warning));
+            assertThat(terminal.getErrorOutput(), containsString("WARNING: " + warning));
             try (Stream<Path> fileStream = Files.list(env.v2().pluginsFile())) {
                 assertThat(fileStream.collect(Collectors.toList()), empty());
             }
@@ -1238,7 +1238,7 @@ public class InstallPluginCommandTests extends ESTestCase {
             terminal.addTextInput("n");
             e = expectThrows(UserException.class, () -> installPlugin(pluginZip, env.v1()));
             assertEquals("installation aborted by user", e.getMessage());
-            assertThat(terminal.getOutput(), containsString("WARNING: " + warning));
+            assertThat(terminal.getErrorOutput(), containsString("WARNING: " + warning));
             try (Stream<Path> fileStream = Files.list(env.v2().pluginsFile())) {
                 assertThat(fileStream.collect(Collectors.toList()), empty());
             }
@@ -1251,7 +1251,7 @@ public class InstallPluginCommandTests extends ESTestCase {
         }
         installPlugin(pluginZip, env.v1());
         for (String warning : warnings) {
-            assertThat(terminal.getOutput(), containsString("WARNING: " + warning));
+            assertThat(terminal.getErrorOutput(), containsString("WARNING: " + warning));
         }
     }
 

distribution/tools/plugin-cli/src/test/java/org/elasticsearch/plugins/ListPluginsCommandTests.java

@@ -247,8 +247,11 @@ public class ListPluginsCommandTests extends ESTestCase {
         MockTerminal terminal = listPlugins(home);
         String message = "plugin [fake_plugin1] was built for Elasticsearch version 1.0 but version " + Version.CURRENT + " is required";
         assertEquals(
-                "fake_plugin1\n" + "WARNING: " + message + "\n" + "fake_plugin2\n",
-                terminal.getOutput());
+            "fake_plugin1\nfake_plugin2\n",
+            terminal.getOutput());
+        assertEquals(
+                "WARNING: " + message + "\n",
+                terminal.getErrorOutput());
 
         String[] params = {"-s"};
         terminal = listPlugins(home, params);

distribution/tools/plugin-cli/src/test/java/org/elasticsearch/plugins/RemovePluginCommandTests.java

@@ -246,11 +246,14 @@ public class RemovePluginCommandTests extends ESTestCase {
                 return false;
             }
         }.main(new String[] { "-Epath.home=" + home, "fake" }, terminal);
-        try (BufferedReader reader = new BufferedReader(new StringReader(terminal.getOutput()))) {
+        try (BufferedReader reader = new BufferedReader(new StringReader(terminal.getOutput()));
+             BufferedReader errorReader = new BufferedReader(new StringReader(terminal.getErrorOutput()))
+        ) {
             assertEquals("-> removing [fake]...", reader.readLine());
             assertEquals("ERROR: plugin [fake] not found; run 'elasticsearch-plugin list' to get list of installed plugins",
-                    reader.readLine());
+                    errorReader.readLine());
             assertNull(reader.readLine());
+            assertNull(errorReader.readLine());
         }
     }
 

libs/cli/src/main/java/org/elasticsearch/cli/Command.java

@@ -73,7 +73,7 @@ public abstract class Command implements Closeable {
                         StringWriter sw = new StringWriter();
                         PrintWriter pw = new PrintWriter(sw)) {
                         e.printStackTrace(pw);
-                        terminal.println(sw.toString());
+                        terminal.errorPrintln(sw.toString());
                     } catch (final IOException impossible) {
                         // StringWriter#close declares a checked IOException from the Closeable interface but the Javadocs for StringWriter
                         // say that an exception here is impossible
@@ -89,14 +89,15 @@ public abstract class Command implements Closeable {
         try {
             mainWithoutErrorHandling(args, terminal);
         } catch (OptionException e) {
-            printHelp(terminal);
-            terminal.println(Terminal.Verbosity.SILENT, "ERROR: " + e.getMessage());
+            // print help to stderr on exceptions
+            printHelp(terminal, true);
+            terminal.errorPrintln(Terminal.Verbosity.SILENT, "ERROR: " + e.getMessage());
             return ExitCodes.USAGE;
         } catch (UserException e) {
             if (e.exitCode == ExitCodes.USAGE) {
-                printHelp(terminal);
+                printHelp(terminal, true);
             }
-            terminal.println(Terminal.Verbosity.SILENT, "ERROR: " + e.getMessage());
+            terminal.errorPrintln(Terminal.Verbosity.SILENT, "ERROR: " + e.getMessage());
             return e.exitCode;
         }
         return ExitCodes.OK;
@@ -109,7 +110,7 @@ public abstract class Command implements Closeable {
         final OptionSet options = parser.parse(args);
 
         if (options.has(helpOption)) {
-            printHelp(terminal);
+            printHelp(terminal, false);
             return;
         }
 
@@ -125,11 +126,17 @@ public abstract class Command implements Closeable {
     }
 
     /** Prints a help message for the command to the terminal. */
-    private void printHelp(Terminal terminal) throws IOException {
-        terminal.println(description);
-        terminal.println("");
-        printAdditionalHelp(terminal);
-        parser.printHelpOn(terminal.getWriter());
+    private void printHelp(Terminal terminal, boolean toStdError) throws IOException {
+        if (toStdError) {
+            terminal.errorPrintln(description);
+            terminal.errorPrintln("");
+            parser.printHelpOn(terminal.getErrorWriter());
+        } else {
+            terminal.println(description);
+            terminal.println("");
+            printAdditionalHelp(terminal);
+            parser.printHelpOn(terminal.getWriter());
+        }
     }
 
     /** Prints additional help information, specific to the command */

libs/cli/src/main/java/org/elasticsearch/cli/Terminal.java

@@ -39,9 +39,17 @@ import java.util.Locale;
 */
 public abstract class Terminal {
 
+    /** Writer to standard error - not supplied by the {@link Console} API, so we share with subclasses */
+    private static final PrintWriter ERROR_WRITER = newErrorWriter();
+
     /** The default terminal implementation, which will be a console if available, or stdout/stderr if not. */
     public static final Terminal DEFAULT = ConsoleTerminal.isSupported() ? new ConsoleTerminal() : new SystemTerminal();
 
+    @SuppressForbidden(reason = "Writer for System.err")
+    private static PrintWriter newErrorWriter() {
+        return new PrintWriter(System.err);
+    }
+
     /** Defines the available verbosity levels of messages to be printed. */
     public enum Verbosity {
         SILENT, /* always printed */
@@ -70,9 +78,14 @@ public abstract class Terminal {
     /** Reads password text from the terminal input. See {@link Console#readPassword()}}. */
     public abstract char[] readSecret(String prompt);
 
-    /** Returns a Writer which can be used to write to the terminal directly. */
+    /** Returns a Writer which can be used to write to the terminal directly using standard output. */
     public abstract PrintWriter getWriter();
 
+    /** Returns a Writer which can be used to write to the terminal directly using standard error. */
+    public PrintWriter getErrorWriter() {
+        return ERROR_WRITER;
+    }
+
     /** Prints a line to the terminal at {@link Verbosity#NORMAL} verbosity level. */
     public final void println(String msg) {
         println(Verbosity.NORMAL, msg);
@@ -83,14 +96,35 @@ public abstract class Terminal {
         print(verbosity, msg + lineSeparator);
     }
 
-    /** Prints message to the terminal at {@code verbosity} level, without a newline. */
+    /** Prints message to the terminal's standard output at {@code verbosity} level, without a newline. */
     public final void print(Verbosity verbosity, String msg) {
+        print(verbosity, msg, false);
+    }
+
+    /** Prints message to the terminal at {@code verbosity} level, without a newline. */
+    private void print(Verbosity verbosity, String msg, boolean isError) {
         if (isPrintable(verbosity)) {
-            getWriter().print(msg);
-            getWriter().flush();
+            PrintWriter writer = isError ? getErrorWriter() : getWriter();
+            writer.print(msg);
+            writer.flush();
         }
     }
 
+    /** Prints a line to the terminal's standard error at {@link Verbosity#NORMAL} verbosity level, without a newline. */
+    public final void errorPrint(Verbosity verbosity, String msg) {
+        print(verbosity, msg, true);
+    }
+
+    /** Prints a line to the terminal's standard error at {@link Verbosity#NORMAL} verbosity level. */
+    public final void errorPrintln(String msg) {
+        errorPrintln(Verbosity.NORMAL, msg);
+    }
+
+    /** Prints a line to the terminal's standard error at {@code verbosity} level. */
+    public final void errorPrintln(Verbosity verbosity, String msg) {
+        errorPrint(verbosity, msg + lineSeparator);
+    }
+
     /** Checks if is enough {@code verbosity} level to be printed */
     public final boolean isPrintable(Verbosity verbosity) {
         return this.verbosity.ordinal() >= verbosity.ordinal();
@@ -110,7 +144,7 @@ public abstract class Terminal {
             answer = answer.toLowerCase(Locale.ROOT);
             boolean answerYes = answer.equals("y");
             if (answerYes == false && answer.equals("n") == false) {
-                println("Did not understand answer '" + answer + "'");
+                errorPrintln("Did not understand answer '" + answer + "'");
                 continue;
             }
             return answerYes;
@@ -165,7 +199,7 @@ public abstract class Terminal {
 
         @Override
         public String readText(String text) {
-            getWriter().print(text);
+            getErrorWriter().print(text); // prompts should go to standard error to avoid mixing with list output
             BufferedReader reader = new BufferedReader(new InputStreamReader(System.in, Charset.defaultCharset()));
             try {
                 final String line = reader.readLine();

qa/evil-tests/src/test/java/org/elasticsearch/bootstrap/EvilElasticsearchCliTests.java

@@ -40,7 +40,7 @@ public class EvilElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
                 ExitCodes.OK,
                 true,
-                output -> {},
+                (output, error) -> {},
                 (foreground, pidFile, quiet, esSettings) -> {
                     Settings settings = esSettings.settings();
                     assertThat(settings.keySet(), hasSize(2));
@@ -55,7 +55,7 @@ public class EvilElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
                 ExitCodes.OK,
                 true,
-                output -> {},
+                (output, error) -> {},
                 (foreground, pidFile, quiet, esSettings) -> {
                     Settings settings = esSettings.settings();
                     assertThat(settings.keySet(), hasSize(2));

qa/evil-tests/src/test/java/org/elasticsearch/cli/EvilCommandTests.java

@@ -55,7 +55,7 @@ public class EvilCommandTests extends ESTestCase {
         command.getShutdownHookThread().run();
         command.getShutdownHookThread().join();
         assertTrue(closed.get());
-        final String output = terminal.getOutput();
+        final String output = terminal.getErrorOutput();
         if (shouldThrow) {
             // ensure that we dump the exception
             assertThat(output, containsString("java.io.IOException: fail"));

qa/os/src/test/java/org/elasticsearch/packaging/test/ArchiveTests.java

@@ -373,7 +373,7 @@ public class ArchiveTests extends PackagingTestCase {
                 // Ensure that the exit code from the java command is passed back up through the shell script
                 result = sh.runIgnoreExitCode(bin.elasticsearchCertutil + " invalid-command");
                 assertThat(result.exitCode, is(not(0)));
-                assertThat(result.stdout, containsString("Unknown command [invalid-command]"));
+                assertThat(result.stderr, containsString("Unknown command [invalid-command]"));
             };
             Platforms.onLinux(action);
             Platforms.onWindows(action);

server/src/main/java/org/elasticsearch/plugins/PluginSecurity.java

@@ -55,15 +55,15 @@ class PluginSecurity {
             // sort permissions in a reasonable order
             Collections.sort(requested);
 
-            terminal.println(Verbosity.NORMAL, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
-            terminal.println(Verbosity.NORMAL, "@     WARNING: plugin requires additional permissions     @");
-            terminal.println(Verbosity.NORMAL, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
+            terminal.errorPrintln(Verbosity.NORMAL, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
+            terminal.errorPrintln(Verbosity.NORMAL, "@     WARNING: plugin requires additional permissions     @");
+            terminal.errorPrintln(Verbosity.NORMAL, "@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
             // print all permissions:
             for (String permission : requested) {
-                terminal.println(Verbosity.NORMAL, "* " + permission);
+                terminal.errorPrintln(Verbosity.NORMAL, "* " + permission);
             }
-            terminal.println(Verbosity.NORMAL, "See http://docs.oracle.com/javase/8/docs/technotes/guides/security/permissions.html");
-            terminal.println(Verbosity.NORMAL, "for descriptions of what these permissions allow and the associated risks.");
+            terminal.errorPrintln(Verbosity.NORMAL, "See http://docs.oracle.com/javase/8/docs/technotes/guides/security/permissions.html");
+            terminal.errorPrintln(Verbosity.NORMAL, "for descriptions of what these permissions allow and the associated risks.");
             prompt(terminal, batch);
         }
     }

server/src/test/java/org/elasticsearch/bootstrap/ElasticsearchCliTests.java

@@ -26,7 +26,7 @@ import org.elasticsearch.monitor.jvm.JvmInfo;
 
 import java.nio.file.Path;
 import java.util.Locale;
-import java.util.function.Consumer;
+import java.util.function.BiConsumer;
 
 import static org.hamcrest.CoreMatchers.containsString;
 import static org.hamcrest.CoreMatchers.equalTo;
@@ -53,15 +53,15 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
     private void runTestThatVersionIsMutuallyExclusiveToOtherOptions(String... args) throws Exception {
         runTestVersion(
                 ExitCodes.USAGE,
-                output -> assertThat(
-                        output,
+                (output, error) -> assertThat(
+                        error,
                         allOf(containsString("ERROR:"),
                               containsString("are unavailable given other options on the command line"))),
                 args);
     }
 
     private void runTestThatVersionIsReturned(String... args) throws Exception {
-        runTestVersion(ExitCodes.OK, output -> {
+        runTestVersion(ExitCodes.OK, (output, error) -> {
             assertThat(output, containsString("Version: " + Build.CURRENT.getQualifiedVersion()));
             final String expectedBuildOutput = String.format(
                     Locale.ROOT,
@@ -75,7 +75,7 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         }, args);
     }
 
-    private void runTestVersion(int expectedStatus, Consumer<String> outputConsumer, String... args) throws Exception {
+    private void runTestVersion(int expectedStatus, BiConsumer<String, String> outputConsumer, String... args) throws Exception {
         runTest(expectedStatus, false, outputConsumer, (foreground, pidFile, quiet, esSettings) -> {}, args);
     }
 
@@ -83,19 +83,19 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
             ExitCodes.USAGE,
             false,
-            output -> assertThat(output, containsString("Positional arguments not allowed, found [foo]")),
+            (output, error) -> assertThat(error, containsString("Positional arguments not allowed, found [foo]")),
             (foreground, pidFile, quiet, esSettings) -> {},
             "foo");
         runTest(
             ExitCodes.USAGE,
             false,
-            output -> assertThat(output, containsString("Positional arguments not allowed, found [foo, bar]")),
+            (output, error) -> assertThat(error, containsString("Positional arguments not allowed, found [foo, bar]")),
             (foreground, pidFile, quiet, esSettings) -> {},
             "foo", "bar");
         runTest(
             ExitCodes.USAGE,
             false,
-            output -> assertThat(output, containsString("Positional arguments not allowed, found [foo]")),
+            (output, error) -> assertThat(error, containsString("Positional arguments not allowed, found [foo]")),
             (foreground, pidFile, quiet, esSettings) -> {},
             "-E", "foo=bar", "foo", "-E", "baz=qux");
     }
@@ -104,12 +104,12 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         Path tmpDir = createTempDir();
         Path pidFile = tmpDir.resolve("pid");
         runPidFileTest(ExitCodes.USAGE, false,
-                output -> assertThat(output, containsString("Option p/pidfile requires an argument")), pidFile, "-p");
-        runPidFileTest(ExitCodes.OK, true, output -> {}, pidFile, "-p", pidFile.toString());
-        runPidFileTest(ExitCodes.OK, true, output -> {}, pidFile, "--pidfile", tmpDir.toString() + "/pid");
+            (output, error) -> assertThat(error, containsString("Option p/pidfile requires an argument")), pidFile, "-p");
+        runPidFileTest(ExitCodes.OK, true, (output, error) -> {}, pidFile, "-p", pidFile.toString());
+        runPidFileTest(ExitCodes.OK, true, (output, error) -> {}, pidFile, "--pidfile", tmpDir.toString() + "/pid");
     }
 
-    private void runPidFileTest(final int expectedStatus, final boolean expectedInit, Consumer<String> outputConsumer,
+    private void runPidFileTest(final int expectedStatus, final boolean expectedInit, BiConsumer<String, String> outputConsumer,
                                 Path expectedPidFile, final String... args)
             throws Exception {
         runTest(
@@ -130,7 +130,7 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
                 ExitCodes.OK,
                 true,
-                output -> {},
+                (output, error) -> {},
                 (foreground, pidFile, quiet, esSettings) -> assertThat(foreground, equalTo(!expectedDaemonize)),
                 args);
     }
@@ -145,7 +145,7 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
                 ExitCodes.OK,
                 true,
-                output -> {},
+                (output, error) -> {},
                 (foreground, pidFile, quiet, esSettings) -> assertThat(quiet, equalTo(expectedQuiet)),
                 args);
     }
@@ -154,7 +154,7 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
                 ExitCodes.OK,
                 true,
-                output -> {},
+                (output, error) -> {},
                 (foreground, pidFile, quiet, env) -> {
                     Settings settings = env.settings();
                     assertEquals("bar", settings.get("foo"));
@@ -167,7 +167,7 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
                 ExitCodes.USAGE,
                 false,
-                output -> assertThat(output, containsString("setting [foo] must not be empty")),
+                (output, error) -> assertThat(error, containsString("setting [foo] must not be empty")),
                 (foreground, pidFile, quiet, esSettings) -> {},
                 "-E", "foo=");
     }
@@ -176,7 +176,7 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
                 ExitCodes.USAGE,
                 false,
-                output -> assertThat(output, containsString("setting [foo] already set, saw [bar] and [baz]")),
+                (output, error) -> assertThat(error, containsString("setting [foo] already set, saw [bar] and [baz]")),
                 (foreground, pidFile, quiet, initialEnv) -> {},
                 "-E", "foo=bar", "-E", "foo=baz");
     }
@@ -185,7 +185,7 @@ public class ElasticsearchCliTests extends ESElasticsearchCliTestCase {
         runTest(
                 ExitCodes.USAGE,
                 false,
-                output -> assertThat(output, containsString("network.host is not a recognized option")),
+                (output, error) -> assertThat(error, containsString("network.host is not a recognized option")),
                 (foreground, pidFile, quiet, esSettings) -> {},
                 "--network.host");
     }

server/src/test/java/org/elasticsearch/cli/CommandTests.java

@@ -110,6 +110,31 @@ public class CommandTests extends ESTestCase {
         assertFalse(command.executed);
     }
 
+    public void testUnknownOptions() throws Exception {
+        NoopCommand command = new NoopCommand();
+        MockTerminal terminal = new MockTerminal();
+        String[] args = {"-Z"};
+        int status = command.main(args, terminal);
+        String output = terminal.getOutput();
+        String error = terminal.getErrorOutput();
+        assertEquals(output, ExitCodes.USAGE, status);
+        assertTrue(error, error.contains("Does nothing"));
+        assertFalse(output, output.contains("Some extra help")); // extra help not printed for usage errors
+        assertTrue(error, error.contains("ERROR: Z is not a recognized option"));
+        assertFalse(command.executed);
+
+        command = new NoopCommand();
+        String[] args2 = {"--foobar"};
+        status = command.main(args2, terminal);
+        output = terminal.getOutput();
+        error = terminal.getErrorOutput();
+        assertEquals(output, ExitCodes.USAGE, status);
+        assertTrue(error, error.contains("Does nothing"));
+        assertFalse(output, output.contains("Some extra help")); // extra help not printed for usage errors
+        assertTrue(error, error.contains("ERROR: Z is not a recognized option"));
+        assertFalse(command.executed);
+    }
+
     public void testVerbositySilentAndVerbose() throws Exception {
         MockTerminal terminal = new MockTerminal();
         NoopCommand command = new NoopCommand();
@@ -155,8 +180,9 @@ public class CommandTests extends ESTestCase {
         String[] args = {};
         int status = command.main(args, terminal);
         String output = terminal.getOutput();
+        String error = terminal.getErrorOutput();
         assertEquals(output, ExitCodes.DATA_ERROR, status);
-        assertTrue(output, output.contains("ERROR: Bad input"));
+        assertTrue(error, error.contains("ERROR: Bad input"));
     }
 
     public void testUsageError() throws Exception {
@@ -165,9 +191,10 @@ public class CommandTests extends ESTestCase {
         String[] args = {};
         int status = command.main(args, terminal);
         String output = terminal.getOutput();
+        String error = terminal.getErrorOutput();
         assertEquals(output, ExitCodes.USAGE, status);
-        assertTrue(output, output.contains("Throws a usage error"));
-        assertTrue(output, output.contains("ERROR: something was no good"));
+        assertTrue(error, error.contains("Throws a usage error"));
+        assertTrue(error, error.contains("ERROR: something was no good"));
     }
 
 }

server/src/test/java/org/elasticsearch/cli/TerminalTests.java

@@ -41,6 +41,26 @@ public class TerminalTests extends ESTestCase {
         assertPrinted(terminal, Terminal.Verbosity.VERBOSE, "text");
     }
 
+    public void testErrorVerbosity() throws Exception {
+        MockTerminal terminal = new MockTerminal();
+        terminal.setVerbosity(Terminal.Verbosity.SILENT);
+        assertErrorPrinted(terminal, Terminal.Verbosity.SILENT, "text");
+        assertErrorNotPrinted(terminal, Terminal.Verbosity.NORMAL, "text");
+        assertErrorNotPrinted(terminal, Terminal.Verbosity.VERBOSE, "text");
+
+        terminal = new MockTerminal();
+        assertErrorPrinted(terminal, Terminal.Verbosity.SILENT, "text");
+        assertErrorPrinted(terminal, Terminal.Verbosity.NORMAL, "text");
+        assertErrorNotPrinted(terminal, Terminal.Verbosity.VERBOSE, "text");
+
+        terminal = new MockTerminal();
+        terminal.setVerbosity(Terminal.Verbosity.VERBOSE);
+        assertErrorPrinted(terminal, Terminal.Verbosity.SILENT, "text");
+        assertErrorPrinted(terminal, Terminal.Verbosity.NORMAL, "text");
+        assertErrorPrinted(terminal, Terminal.Verbosity.VERBOSE, "text");
+    }
+
+
     public void testEscaping() throws Exception {
         MockTerminal terminal = new MockTerminal();
         assertPrinted(terminal, Terminal.Verbosity.NORMAL, "This message contains percent like %20n");
@@ -87,4 +107,18 @@ public class TerminalTests extends ESTestCase {
         String output = logTerminal.getOutput();
         assertTrue(output, output.isEmpty());
     }
+
+    private void assertErrorPrinted(MockTerminal logTerminal, Terminal.Verbosity verbosity, String text) throws Exception {
+        logTerminal.errorPrintln(verbosity, text);
+        String output = logTerminal.getErrorOutput();
+        assertTrue(output, output.contains(text));
+        logTerminal.reset();
+    }
+
+    private void assertErrorNotPrinted(MockTerminal logTerminal, Terminal.Verbosity verbosity, String text) throws Exception {
+        logTerminal.errorPrintln(verbosity, text);
+        String output = logTerminal.getErrorOutput();
+        assertTrue(output, output.isEmpty());
+    }
+
 }

test/framework/src/main/java/org/elasticsearch/bootstrap/ESElasticsearchCliTestCase.java

@@ -28,7 +28,7 @@ import org.elasticsearch.test.ESTestCase;
 import java.nio.file.Path;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.function.Consumer;
+import java.util.function.BiConsumer;
 
 import static org.hamcrest.CoreMatchers.equalTo;
 
@@ -41,7 +41,7 @@ abstract class ESElasticsearchCliTestCase extends ESTestCase {
     void runTest(
             final int expectedStatus,
             final boolean expectedInit,
-            final Consumer<String> outputConsumer,
+            final BiConsumer<String, String> outputConsumer,
             final InitConsumer initConsumer,
             final String... args) throws Exception {
         final MockTerminal terminal = new MockTerminal();
@@ -69,11 +69,12 @@ abstract class ESElasticsearchCliTestCase extends ESTestCase {
             }, terminal);
             assertThat(status, equalTo(expectedStatus));
             assertThat(init.get(), equalTo(expectedInit));
-            outputConsumer.accept(terminal.getOutput());
+            outputConsumer.accept(terminal.getOutput(), terminal.getErrorOutput());
         } catch (Exception e) {
             // if an unexpected exception is thrown, we log
             // terminal output to aid debugging
-            logger.info(terminal.getOutput());
+            logger.info("Stdout:\n" + terminal.getOutput());
+            logger.info("Stderr:\n" + terminal.getErrorOutput());
             // rethrow so the test fails
             throw e;
         }

test/framework/src/main/java/org/elasticsearch/cli/MockTerminal.java

@@ -33,8 +33,10 @@ import java.util.List;
  */
 public class MockTerminal extends Terminal {
 
-    private final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-    private final PrintWriter writer = new PrintWriter(new OutputStreamWriter(buffer, StandardCharsets.UTF_8));
+    private final ByteArrayOutputStream stdoutBuffer = new ByteArrayOutputStream();
+    private final ByteArrayOutputStream stderrBuffer = new ByteArrayOutputStream();
+    private final PrintWriter writer = new PrintWriter(new OutputStreamWriter(stdoutBuffer, StandardCharsets.UTF_8));
+    private final PrintWriter errorWriter = new PrintWriter(new OutputStreamWriter(stderrBuffer, StandardCharsets.UTF_8));
 
     // A deque would be a perfect data structure for the FIFO queue of input values needed here. However,
     // to support the valid return value of readText being null (defined by Console), we need to be able
@@ -73,6 +75,11 @@ public class MockTerminal extends Terminal {
         return writer;
     }
 
+    @Override
+    public PrintWriter getErrorWriter() {
+        return errorWriter;
+    }
+
     /** Adds an an input that will be return from {@link #readText(String)}. Values are read in FIFO order. */
     public void addTextInput(String input) {
         textInput.add(input);
@@ -85,12 +92,18 @@ public class MockTerminal extends Terminal {
 
     /** Returns all output written to this terminal. */
     public String getOutput() throws UnsupportedEncodingException {
-        return buffer.toString("UTF-8");
+        return stdoutBuffer.toString("UTF-8");
+    }
+
+    /** Returns all output written to this terminal. */
+    public String getErrorOutput() throws UnsupportedEncodingException {
+        return stderrBuffer.toString("UTF-8");
     }
 
     /** Wipes the input and output. */
     public void reset() {
-        buffer.reset();
+        stdoutBuffer.reset();
+        stderrBuffer.reset();
         textIndex = 0;
         textInput.clear();
         secretIndex = 0;

x-pack/plugin/security/cli/src/main/java/org/elasticsearch/xpack/security/cli/CertificateGenerateTool.java

@@ -285,12 +285,12 @@ public class CertificateGenerateTool extends EnvironmentAwareCommand {
             final List<String> errors = certInfo.validate();
             if (errors.size() > 0) {
                 hasError = true;
-                terminal.println(Terminal.Verbosity.SILENT, "Configuration for instance " + certInfo.name.originalName
+                terminal.errorPrintln(Terminal.Verbosity.SILENT, "Configuration for instance " + certInfo.name.originalName
                     + " has invalid details");
                 for (String message : errors) {
-                    terminal.println(Terminal.Verbosity.SILENT, " * " + message);
+                    terminal.errorPrintln(Terminal.Verbosity.SILENT, " * " + message);
                 }
-                terminal.println("");
+                terminal.errorPrintln("");
             }
         }
         if (hasError) {

x-pack/plugin/security/cli/src/main/java/org/elasticsearch/xpack/security/cli/CertificateTool.java

@@ -417,7 +417,7 @@ public class CertificateTool extends LoggingAwareMultiCommand {
                 if (validationErrors.isEmpty()) {
                     return Collections.singleton(information);
                 } else {
-                    validationErrors.forEach(terminal::println);
+                    validationErrors.forEach(terminal::errorPrintln);
                     return Collections.emptyList();
                 }
             }
@@ -477,7 +477,7 @@ public class CertificateTool extends LoggingAwareMultiCommand {
                 if (Name.isValidFilename(filename)) {
                     return filename;
                 } else {
-                    terminal.println(Terminal.Verbosity.SILENT, "'" + filename + "' is not a valid filename");
+                    terminal.errorPrintln(Terminal.Verbosity.SILENT, "'" + filename + "' is not a valid filename");
                     continue;
                 }
             }
@@ -891,11 +891,12 @@ public class CertificateTool extends LoggingAwareMultiCommand {
             final List<String> errors = certInfo.validate();
             if (errors.size() > 0) {
                 hasError = true;
-                terminal.println(Verbosity.SILENT, "Configuration for instance " + certInfo.name.originalName + " has invalid details");
+                terminal.errorPrintln(Verbosity.SILENT, "Configuration for instance " + certInfo.name.originalName +
+                    " has invalid details");
                 for (String message : errors) {
-                    terminal.println(Verbosity.SILENT, " * " + message);
+                    terminal.errorPrintln(Verbosity.SILENT, " * " + message);
                 }
-                terminal.println("");
+                terminal.errorPrintln("");
             }
         }
         if (hasError) {
@@ -961,7 +962,7 @@ public class CertificateTool extends LoggingAwareMultiCommand {
             return;
         }
         if (Files.exists(parent)) {
-            terminal.println(Terminal.Verbosity.SILENT, "Path " + parent + " exists, but is not a directory. Cannot write to " + path);
+            terminal.errorPrintln(Terminal.Verbosity.SILENT, "Path " + parent + " exists, but is not a directory. Cannot write to " + path);
             throw new UserException(ExitCodes.CANT_CREATE, "Cannot write to " + path);
         }
         if (terminal.promptYesNo("Directory " + parent + " does not exist. Do you want to create it?", true)) {

x-pack/plugin/security/cli/src/test/java/org/elasticsearch/xpack/security/cli/CertificateToolTests.java

@@ -242,8 +242,8 @@ public class CertificateToolTests extends ESTestCase {
                 () -> CertificateTool.parseAndValidateFile(terminal, instanceFile));
         assertThat(exception.getMessage(), containsString("invalid configuration"));
         assertThat(exception.getMessage(), containsString(instanceFile.toString()));
-        assertThat(terminal.getOutput(), containsString("THIS=not a,valid DN"));
-        assertThat(terminal.getOutput(), containsString("could not be converted to a valid DN"));
+        assertThat(terminal.getErrorOutput(), containsString("THIS=not a,valid DN"));
+        assertThat(terminal.getErrorOutput(), containsString("could not be converted to a valid DN"));
     }
 
     public void testGeneratingCsr() throws Exception {

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/esnative/tool/SetupPasswordTool.java

@@ -195,15 +195,15 @@ public class SetupPasswordTool extends LoggingAwareMultiCommand {
                 SecureString password1 = new SecureString(terminal.readSecret("Enter password for [" + user + "]: "));
                 Validation.Error err = Validation.Users.validatePassword(password1);
                 if (err != null) {
-                    terminal.println(err.toString());
-                    terminal.println("Try again.");
+                    terminal.errorPrintln(err.toString());
+                    terminal.errorPrintln("Try again.");
                     password1.close();
                     continue;
                 }
                 try (SecureString password2 = new SecureString(terminal.readSecret("Reenter password for [" + user + "]: "))) {
                     if (password1.equals(password2) == false) {
-                        terminal.println("Passwords do not match.");
-                        terminal.println("Try again.");
+                        terminal.errorPrintln("Passwords do not match.");
+                        terminal.errorPrintln("Try again.");
                         password1.close();
                         continue;
                     }
@@ -302,53 +302,55 @@ public class SetupPasswordTool extends LoggingAwareMultiCommand {
 
                 // keystore password is not valid
                 if (httpCode == HttpURLConnection.HTTP_UNAUTHORIZED) {
-                    terminal.println("");
-                    terminal.println("Failed to authenticate user '" + elasticUser + "' against " + route.toString());
-                    terminal.println("Possible causes include:");
-                    terminal.println(" * The password for the '" + elasticUser + "' user has already been changed on this cluster");
-                    terminal.println(" * Your elasticsearch node is running against a different keystore");
-                    terminal.println("   This tool used the keystore at " + KeyStoreWrapper.keystorePath(env.configFile()));
-                    terminal.println("");
+                    terminal.errorPrintln("");
+                    terminal.errorPrintln("Failed to authenticate user '" + elasticUser + "' against " + route.toString());
+                    terminal.errorPrintln("Possible causes include:");
+                    terminal.errorPrintln(" * The password for the '" + elasticUser + "' user has already been changed on this cluster");
+                    terminal.errorPrintln(" * Your elasticsearch node is running against a different keystore");
+                    terminal.errorPrintln("   This tool used the keystore at " + KeyStoreWrapper.keystorePath(env.configFile()));
+                    terminal.errorPrintln("");
                     throw new UserException(ExitCodes.CONFIG, "Failed to verify bootstrap password");
                 } else if (httpCode != HttpURLConnection.HTTP_OK) {
-                    terminal.println("");
-                    terminal.println("Unexpected response code [" + httpCode + "] from calling GET " + route.toString());
+                    terminal.errorPrintln("");
+                    terminal.errorPrintln("Unexpected response code [" + httpCode + "] from calling GET " + route.toString());
                     XPackSecurityFeatureConfig xPackSecurityFeatureConfig = getXPackSecurityConfig(terminal);
                     if (xPackSecurityFeatureConfig.isAvailable == false) {
-                        terminal.println("It doesn't look like the X-Pack security feature is available on this Elasticsearch node.");
-                        terminal.println("Please check if you have installed a license that allows access to X-Pack Security feature.");
-                        terminal.println("");
+                        terminal.errorPrintln("It doesn't look like the X-Pack security feature is available on this Elasticsearch node.");
+                        terminal.errorPrintln("Please check if you have installed a license that allows access to " +
+                            "X-Pack Security feature.");
+                        terminal.errorPrintln("");
                         throw new UserException(ExitCodes.CONFIG, "X-Pack Security is not available.");
                     }
                     if (xPackSecurityFeatureConfig.isEnabled == false) {
-                        terminal.println("It doesn't look like the X-Pack security feature is enabled on this Elasticsearch node.");
-                        terminal.println("Please check if you have enabled X-Pack security in your elasticsearch.yml configuration file.");
-                        terminal.println("");
+                        terminal.errorPrintln("It doesn't look like the X-Pack security feature is enabled on this Elasticsearch node.");
+                        terminal.errorPrintln("Please check if you have enabled X-Pack security in your elasticsearch.yml " +
+                            "configuration file.");
+                        terminal.errorPrintln("");
                         throw new UserException(ExitCodes.CONFIG, "X-Pack Security is disabled by configuration.");
                     }
-                    terminal.println("X-Pack security feature is available and enabled on this Elasticsearch node.");
-                    terminal.println("Possible causes include:");
-                    terminal.println(" * The relative path of the URL is incorrect. Is there a proxy in-between?");
-                    terminal.println(" * The protocol (http/https) does not match the port.");
-                    terminal.println(" * Is this really an Elasticsearch server?");
-                    terminal.println("");
+                    terminal.errorPrintln("X-Pack security feature is available and enabled on this Elasticsearch node.");
+                    terminal.errorPrintln("Possible causes include:");
+                    terminal.errorPrintln(" * The relative path of the URL is incorrect. Is there a proxy in-between?");
+                    terminal.errorPrintln(" * The protocol (http/https) does not match the port.");
+                    terminal.errorPrintln(" * Is this really an Elasticsearch server?");
+                    terminal.errorPrintln("");
                     throw new UserException(ExitCodes.CONFIG, "Unknown error");
                 }
             } catch (SSLException e) {
-                terminal.println("");
-                terminal.println("SSL connection to " + route.toString() + " failed: " + e.getMessage());
-                terminal.println("Please check the elasticsearch SSL settings under " + XPackSettings.HTTP_SSL_PREFIX);
-                terminal.println(Verbosity.VERBOSE, "");
-                terminal.println(Verbosity.VERBOSE, ExceptionsHelper.stackTrace(e));
-                terminal.println("");
+                terminal.errorPrintln("");
+                terminal.errorPrintln("SSL connection to " + route.toString() + " failed: " + e.getMessage());
+                terminal.errorPrintln("Please check the elasticsearch SSL settings under " + XPackSettings.HTTP_SSL_PREFIX);
+                terminal.errorPrintln(Verbosity.VERBOSE, "");
+                terminal.errorPrintln(Verbosity.VERBOSE, ExceptionsHelper.stackTrace(e));
+                terminal.errorPrintln("");
                 throw new UserException(ExitCodes.CONFIG,
                         "Failed to establish SSL connection to elasticsearch at " + route.toString() + ". ", e);
             } catch (IOException e) {
-                terminal.println("");
-                terminal.println("Connection failure to: " + route.toString() + " failed: " + e.getMessage());
-                terminal.println(Verbosity.VERBOSE, "");
-                terminal.println(Verbosity.VERBOSE, ExceptionsHelper.stackTrace(e));
-                terminal.println("");
+                terminal.errorPrintln("");
+                terminal.errorPrintln("Connection failure to: " + route.toString() + " failed: " + e.getMessage());
+                terminal.errorPrintln(Verbosity.VERBOSE, "");
+                terminal.errorPrintln(Verbosity.VERBOSE, ExceptionsHelper.stackTrace(e));
+                terminal.errorPrintln("");
                 throw new UserException(ExitCodes.CONFIG,
                         "Failed to connect to elasticsearch at " + route.toString() + ". Is the URL correct and elasticsearch running?", e);
             }
@@ -361,19 +363,20 @@ public class SetupPasswordTool extends LoggingAwareMultiCommand {
             final HttpResponse httpResponse =
                     client.execute("GET", route, elasticUser, elasticUserPassword, () -> null, is -> responseBuilder(is, terminal));
             if (httpResponse.getHttpStatus() != HttpURLConnection.HTTP_OK) {
-                terminal.println("");
-                terminal.println("Unexpected response code [" + httpResponse.getHttpStatus() + "] from calling GET " + route.toString());
+                terminal.errorPrintln("");
+                terminal.errorPrintln("Unexpected response code [" + httpResponse.getHttpStatus() + "] from calling GET " +
+                    route.toString());
                 if (httpResponse.getHttpStatus() == HttpURLConnection.HTTP_BAD_REQUEST) {
-                    terminal.println("It doesn't look like the X-Pack is available on this Elasticsearch node.");
-                    terminal.println("Please check that you have followed all installation instructions and that this tool");
-                    terminal.println("   is pointing to the correct Elasticsearch server.");
-                    terminal.println("");
+                    terminal.errorPrintln("It doesn't look like the X-Pack is available on this Elasticsearch node.");
+                    terminal.errorPrintln("Please check that you have followed all installation instructions and that this tool");
+                    terminal.errorPrintln("   is pointing to the correct Elasticsearch server.");
+                    terminal.errorPrintln("");
                     throw new UserException(ExitCodes.CONFIG, "X-Pack is not available on this Elasticsearch node.");
                 } else {
-                    terminal.println("* Try running this tool again.");
-                    terminal.println("* Verify that the tool is pointing to the correct Elasticsearch server.");
-                    terminal.println("* Check the elasticsearch logs for additional error details.");
-                    terminal.println("");
+                    terminal.errorPrintln("* Try running this tool again.");
+                    terminal.errorPrintln("* Verify that the tool is pointing to the correct Elasticsearch server.");
+                    terminal.errorPrintln("* Check the elasticsearch logs for additional error details.");
+                    terminal.errorPrintln("");
                     throw new UserException(ExitCodes.TEMP_FAILURE, "Failed to determine x-pack security feature configuration.");
                 }
             }
@@ -406,33 +409,34 @@ public class SetupPasswordTool extends LoggingAwareMultiCommand {
             final HttpResponse httpResponse = client.execute("GET", route, elasticUser, elasticUserPassword, () -> null,
                     is -> responseBuilder(is, terminal));
             if (httpResponse.getHttpStatus() != HttpURLConnection.HTTP_OK) {
-                terminal.println("");
-                terminal.println("Failed to determine the health of the cluster running at " + url);
-                terminal.println("Unexpected response code [" + httpResponse.getHttpStatus() + "] from calling GET " + route.toString());
+                terminal.errorPrintln("");
+                terminal.errorPrintln("Failed to determine the health of the cluster running at " + url);
+                terminal.errorPrintln("Unexpected response code [" + httpResponse.getHttpStatus() + "] from calling GET " +
+                    route.toString());
                 final String cause = getErrorCause(httpResponse);
                 if (cause != null) {
-                    terminal.println("Cause: " + cause);
+                    terminal.errorPrintln("Cause: " + cause);
                 }
             } else {
                 final String clusterStatus = Objects.toString(httpResponse.getResponseBody().get("status"), "");
                 if (clusterStatus.isEmpty()) {
-                    terminal.println("");
-                    terminal.println("Failed to determine the health of the cluster running at " + url);
-                    terminal.println("Could not find a 'status' value at " + route.toString());
+                    terminal.errorPrintln("");
+                    terminal.errorPrintln("Failed to determine the health of the cluster running at " + url);
+                    terminal.errorPrintln("Could not find a 'status' value at " + route.toString());
                 } else if ("red".equalsIgnoreCase(clusterStatus)) {
-                    terminal.println("");
-                    terminal.println("Your cluster health is currently RED.");
-                    terminal.println("This means that some cluster data is unavailable and your cluster is not fully functional.");
+                    terminal.errorPrintln("");
+                    terminal.errorPrintln("Your cluster health is currently RED.");
+                    terminal.errorPrintln("This means that some cluster data is unavailable and your cluster is not fully functional.");
                 } else {
                     // Cluster is yellow/green -> all OK
                     return;
                 }
             }
-            terminal.println("");
-            terminal.println(
+            terminal.errorPrintln("");
+            terminal.errorPrintln(
                     "It is recommended that you resolve the issues with your cluster before running elasticsearch-setup-passwords.");
-            terminal.println("It is very likely that the password changes will fail when run against an unhealthy cluster.");
-            terminal.println("");
+            terminal.errorPrintln("It is very likely that the password changes will fail when run against an unhealthy cluster.");
+            terminal.errorPrintln("");
             if (shouldPrompt) {
                 final boolean keepGoing = terminal.promptYesNo("Do you want to continue with the password setup process", false);
                 if (keepGoing == false) {
@@ -465,28 +469,28 @@ public class SetupPasswordTool extends LoggingAwareMultiCommand {
                     }
                 }, is -> responseBuilder(is, terminal));
                 if (httpResponse.getHttpStatus() != HttpURLConnection.HTTP_OK) {
-                    terminal.println("");
-                    terminal.println(
+                    terminal.errorPrintln("");
+                    terminal.errorPrintln(
                             "Unexpected response code [" + httpResponse.getHttpStatus() + "] from calling PUT " + route.toString());
                     String cause = getErrorCause(httpResponse);
                     if (cause != null) {
-                        terminal.println("Cause: " + cause);
-                        terminal.println("");
+                        terminal.errorPrintln("Cause: " + cause);
+                        terminal.errorPrintln("");
                     }
-                    terminal.println("Possible next steps:");
-                    terminal.println("* Try running this tool again.");
-                    terminal.println("* Try running with the --verbose parameter for additional messages.");
-                    terminal.println("* Check the elasticsearch logs for additional error details.");
-                    terminal.println("* Use the change password API manually. ");
-                    terminal.println("");
+                    terminal.errorPrintln("Possible next steps:");
+                    terminal.errorPrintln("* Try running this tool again.");
+                    terminal.errorPrintln("* Try running with the --verbose parameter for additional messages.");
+                    terminal.errorPrintln("* Check the elasticsearch logs for additional error details.");
+                    terminal.errorPrintln("* Use the change password API manually. ");
+                    terminal.errorPrintln("");
                     throw new UserException(ExitCodes.TEMP_FAILURE, "Failed to set password for user [" + user + "].");
                 }
             } catch (IOException e) {
-                terminal.println("");
-                terminal.println("Connection failure to: " + route.toString() + " failed: " + e.getMessage());
-                terminal.println(Verbosity.VERBOSE, "");
-                terminal.println(Verbosity.VERBOSE, ExceptionsHelper.stackTrace(e));
-                terminal.println("");
+                terminal.errorPrintln("");
+                terminal.errorPrintln("Connection failure to: " + route.toString() + " failed: " + e.getMessage());
+                terminal.errorPrintln(Verbosity.VERBOSE, "");
+                terminal.errorPrintln(Verbosity.VERBOSE, ExceptionsHelper.stackTrace(e));
+                terminal.errorPrintln("");
                 throw new UserException(ExitCodes.TEMP_FAILURE, "Failed to set password for user [" + user + "].", e);
             }
         }

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/file/tool/UsersTool.java

@@ -475,11 +475,11 @@ public class UsersTool extends LoggingAwareMultiCommand {
         Set<String> knownRoles = Sets.union(FileRolesStore.parseFileForRoleNames(rolesFile, null), ReservedRolesStore.names());
         Set<String> unknownRoles = Sets.difference(Sets.newHashSet(roles), knownRoles);
         if (!unknownRoles.isEmpty()) {
-            terminal.println(String.format(Locale.ROOT, "Warning: The following roles [%s] are not in the [%s] file. Make sure the names " +
-                    "are correct. If the names are correct and the roles were created using the API please disregard this message. " +
-                    "Nonetheless the user will still be associated with all specified roles",
+            terminal.errorPrintln(String.format(Locale.ROOT, "Warning: The following roles [%s] are not in the [%s] file. " +
+                    "Make sure the names are correct. If the names are correct and the roles were created using the API please " +
+                    "disregard this message. Nonetheless the user will still be associated with all specified roles",
                 Strings.collectionToCommaDelimitedString(unknownRoles), rolesFile.toAbsolutePath()));
-            terminal.println("Known roles: " + knownRoles.toString());
+            terminal.errorPrintln("Known roles: " + knownRoles.toString());
         }
     }
 

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/saml/SamlMetadataCommand.java

@@ -224,7 +224,7 @@ public class SamlMetadataCommand extends EnvironmentAwareCommand {
                     if (ContactInfo.TYPES.containsKey(type)) {
                         break;
                     } else {
-                        terminal.println("Type '" + type + "' is not valid. Valid values are "
+                        terminal.errorPrintln("Type '" + type + "' is not valid. Valid values are "
                                 + Strings.collectionToCommaDelimitedString(ContactInfo.TYPES.keySet()));
                     }
                 }
@@ -263,8 +263,8 @@ public class SamlMetadataCommand extends EnvironmentAwareCommand {
             } else {
                 errorMessage = "Error building signing credentials from provided keyPair";
             }
-            terminal.println(Terminal.Verbosity.SILENT, errorMessage);
-            terminal.println("The following errors were found:");
+            terminal.errorPrintln(Terminal.Verbosity.SILENT, errorMessage);
+            terminal.errorPrintln("The following errors were found:");
             printExceptions(terminal, e);
             throw new UserException(ExitCodes.CANT_CREATE, "Unable to create metadata document");
         }
@@ -351,15 +351,16 @@ public class SamlMetadataCommand extends EnvironmentAwareCommand {
             SamlUtils.validate(xmlInput, METADATA_SCHEMA);
             terminal.println(Terminal.Verbosity.VERBOSE, "The generated metadata file conforms to the SAML metadata schema");
         } catch (SAXException e) {
-            terminal.println(Terminal.Verbosity.SILENT, "Error - The generated metadata file does not conform to the SAML metadata schema");
-            terminal.println("While validating " + xml.toString() + " the follow errors were found:");
+            terminal.errorPrintln(Terminal.Verbosity.SILENT, "Error - The generated metadata file does not conform to the " +
+                "SAML metadata schema");
+            terminal.errorPrintln("While validating " + xml.toString() + " the follow errors were found:");
             printExceptions(terminal, e);
             throw new UserException(ExitCodes.CODE_ERROR, "Generated metadata is not valid");
         }
     }
 
     private void printExceptions(Terminal terminal, Throwable throwable) {
-        terminal.println(" - " + throwable.getMessage());
+        terminal.errorPrintln(" - " + throwable.getMessage());
         for (Throwable sup : throwable.getSuppressed()) {
             printExceptions(terminal, sup);
         }
@@ -453,10 +454,10 @@ public class SamlMetadataCommand extends EnvironmentAwareCommand {
                 throw new UserException(ExitCodes.CONFIG, "There is no SAML realm configured in " + env.configFile());
             }
             if (saml.size() > 1) {
-                terminal.println("Using configuration in " + env.configFile());
-                terminal.println("Found multiple SAML realms: "
+                terminal.errorPrintln("Using configuration in " + env.configFile());
+                terminal.errorPrintln("Found multiple SAML realms: "
                         + saml.stream().map(Map.Entry::getKey).map(Object::toString).collect(Collectors.joining(", ")));
-                terminal.println("Use the -" + optionName(realmSpec) + " option to specify an explicit realm");
+                terminal.errorPrintln("Use the -" + optionName(realmSpec) + " option to specify an explicit realm");
                 throw new UserException(ExitCodes.CONFIG,
                         "Found multiple SAML realms, please specify one with '-" + optionName(realmSpec) + "'");
             }

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/support/FileAttributesChecker.java

@@ -51,19 +51,19 @@ public class FileAttributesChecker {
             PosixFileAttributes newAttributes = view.readAttributes();
             PosixFileAttributes oldAttributes = attributes[i];
             if (oldAttributes.permissions().equals(newAttributes.permissions()) == false) {
-                terminal.println(Terminal.Verbosity.SILENT, "WARNING: The file permissions of [" + paths[i] + "] have changed "
+                terminal.errorPrintln(Terminal.Verbosity.SILENT, "WARNING: The file permissions of [" + paths[i] + "] have changed "
                     + "from [" + PosixFilePermissions.toString(oldAttributes.permissions()) + "] "
                     + "to [" + PosixFilePermissions.toString(newAttributes.permissions()) + "]");
-                terminal.println(Terminal.Verbosity.SILENT,
+                terminal.errorPrintln(Terminal.Verbosity.SILENT,
                     "Please ensure that the user account running Elasticsearch has read access to this file!");
             }
             if (oldAttributes.owner().getName().equals(newAttributes.owner().getName()) == false) {
-                terminal.println(Terminal.Verbosity.SILENT, "WARNING: Owner of file [" + paths[i] + "] "
+                terminal.errorPrintln(Terminal.Verbosity.SILENT, "WARNING: Owner of file [" + paths[i] + "] "
                     + "used to be [" + oldAttributes.owner().getName() + "], "
                     + "but now is [" + newAttributes.owner().getName() + "]");
             }
             if (oldAttributes.group().getName().equals(newAttributes.group().getName()) == false) {
-                terminal.println(Terminal.Verbosity.SILENT, "WARNING: Group of file [" + paths[i] + "] "
+                terminal.errorPrintln(Terminal.Verbosity.SILENT, "WARNING: Group of file [" + paths[i] + "] "
                     + "used to be [" + oldAttributes.group().getName() + "], "
                     + "but now is [" + newAttributes.group().getName() + "]");
             }

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/esnative/tool/SetupPasswordToolTests.java

@@ -350,7 +350,7 @@ public class SetupPasswordToolTests extends CommandTestCase {
             fail("Should have thrown exception");
         } catch (UserException e) {
             assertEquals(ExitCodes.OK, e.exitCode);
-            assertThat(terminal.getOutput(), Matchers.containsString("Your cluster health is currently RED."));
+            assertThat(terminal.getErrorOutput(), Matchers.containsString("Your cluster health is currently RED."));
         }
     }
 

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/saml/SamlMetadataCommandTests.java

@@ -165,9 +165,9 @@ public class SamlMetadataCommandTests extends SamlTestCase {
 
         final UserException userException = expectThrows(UserException.class, () -> command.buildEntityDescriptor(terminal, options, env));
         assertThat(userException.getMessage(), containsString("multiple SAML realms"));
-        assertThat(terminal.getOutput(), containsString("saml_a"));
-        assertThat(terminal.getOutput(), containsString("saml_b"));
-        assertThat(terminal.getOutput(), containsString("Use the -realm option"));
+        assertThat(terminal.getErrorOutput(), containsString("saml_a"));
+        assertThat(terminal.getErrorOutput(), containsString("saml_b"));
+        assertThat(terminal.getErrorOutput(), containsString("Use the -realm option"));
     }
 
     public void testSpecifyRealmNameAsParameter() throws Exception {
@@ -423,7 +423,7 @@ public class SamlMetadataCommandTests extends SamlTestCase {
         final UserException userException = expectThrows(UserException.class, () -> command.possiblySignDescriptor(terminal, options,
                 descriptor, env));
         assertThat(userException.getMessage(), containsString("Unable to create metadata document"));
-        assertThat(terminal.getOutput(), containsString("Error parsing Private Key from"));
+        assertThat(terminal.getErrorOutput(), containsString("Error parsing Private Key from"));
     }
 
     public void testSigningMetadataWithPem() throws Exception {

x-pack/qa/security-tools-tests/src/test/java/org/elasticsearch/xpack/security/authc/file/tool/UsersToolTests.java

@@ -299,7 +299,7 @@ public class UsersToolTests extends CommandTestCase {
 
     public void testParseUnknownRole() throws Exception {
         UsersTool.parseRoles(terminal, TestEnvironment.newEnvironment(settings), "test_r1,r2,r3");
-        String output = terminal.getOutput();
+        String output = terminal.getErrorOutput();
         assertTrue(output, output.contains("The following roles [r2,r3] are not in the ["));
     }
 

x-pack/qa/security-tools-tests/src/test/java/org/elasticsearch/xpack/security/support/FileAttributesCheckerTests.java

@@ -28,6 +28,7 @@ public class FileAttributesCheckerTests extends ESTestCase {
         MockTerminal terminal = new MockTerminal();
         checker.check(terminal);
         assertTrue(terminal.getOutput(), terminal.getOutput().isEmpty());
+        assertTrue(terminal.getErrorOutput(), terminal.getErrorOutput().isEmpty());
     }
 
     public void testNoPosix() throws Exception {
@@ -38,6 +39,7 @@ public class FileAttributesCheckerTests extends ESTestCase {
             MockTerminal terminal = new MockTerminal();
             checker.check(terminal);
             assertTrue(terminal.getOutput(), terminal.getOutput().isEmpty());
+            assertTrue(terminal.getErrorOutput(), terminal.getErrorOutput().isEmpty());
         }
     }
 
@@ -51,6 +53,7 @@ public class FileAttributesCheckerTests extends ESTestCase {
             MockTerminal terminal = new MockTerminal();
             checker.check(terminal);
             assertTrue(terminal.getOutput(), terminal.getOutput().isEmpty());
+            assertTrue(terminal.getErrorOutput(), terminal.getErrorOutput().isEmpty());
         }
     }
 
@@ -71,7 +74,7 @@ public class FileAttributesCheckerTests extends ESTestCase {
 
             MockTerminal terminal = new MockTerminal();
             checker.check(terminal);
-            String output = terminal.getOutput();
+            String output = terminal.getErrorOutput();
             assertTrue(output, output.contains("permissions of [" + path + "] have changed"));
         }
     }
@@ -89,7 +92,7 @@ public class FileAttributesCheckerTests extends ESTestCase {
 
             MockTerminal terminal = new MockTerminal();
             checker.check(terminal);
-            String output = terminal.getOutput();
+            String output = terminal.getErrorOutput();
             assertTrue(output, output.contains("Owner of file [" + path + "] used to be"));
         }
     }
@@ -107,7 +110,7 @@ public class FileAttributesCheckerTests extends ESTestCase {
 
             MockTerminal terminal = new MockTerminal();
             checker.check(terminal);
-            String output = terminal.getOutput();
+            String output = terminal.getErrorOutput();
             assertTrue(output, output.contains("Group of file [" + path + "] used to be"));
         }
     }

x-pack/snapshot-tool/src/test/java/org/elasticsearch/snapshots/AbstractCleanupTests.java

@@ -113,6 +113,7 @@ public abstract class AbstractCleanupTests extends ESSingleNodeTestCase {
             }
         } finally {
             logger.info("Cleanup command output:\n" + terminal.getOutput());
+            logger.info("Cleanup command standard error:\n" + terminal.getErrorOutput());
         }
 
         return terminal;