8361613: System.console() should only be available for interactive terminal #26273

naotoj · 2025-07-11T18:46:14Z

In prior JDK releases, System.console() could return a Console instance even when the JVM was not attached to an interactive terminal. This could lead to confusion, particularly when input was not from a keyboard or output was redirected, such as to or from a file or pipe, especially when using methods like readPassword(). Starting with JDK 25, the default behavior has changed: System.console() now returns null if standard input and/or output is redirected. However, if a JLine-based Console implementation is explicitly specified via the system property -Djdk.console=jdk.internal.le, the previous behavior may still occur.
This PR aims to align the behavior of the JLine-based Console implementation with the default System.console() behavior. The actual code change is a one-liner in JdkConsoleProviderImpl.java; the rest of the changes are adjustments to test cases to reflect the updated behavior. A corresponding CSR has also been drafted.

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Change requires CSR request JDK-8361911 to be approved
Commit message must refer to an issue

Issues

JDK-8361613: System.console() should only be available for interactive terminal (Bug - P4)
JDK-8361911: System.console() should only be available for interactive terminal (CSR)

Reviewers

Jan Lahoda (@lahodaj - Reviewer)
Stuart Marks (@stuart-marks - Reviewer)
Alan Bateman (@AlanBateman - Reviewer)

Reviewing

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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk.git pull/26273/head

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bridgekeeper · 2025-07-11T18:46:40Z

👋 Welcome back naoto! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2025-07-11T18:47:12Z

@naotoj This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8361613: System.console() should only be available for interactive terminal

Reviewed-by: jlahoda, smarks, alanb

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 481 new commits pushed to the master branch:

78d50c0: 8358756: [s390x] Test StartupOutput.java crash due to CodeCache size
2e06a91: 8365841: RISC-V: Several IR verification tests fail after JDK-8350960 without Zvfh
ecab52c: 8365610: Sort share/jfr includes
... and 478 more: https://git.openjdk.org/jdk/compare/3d74cbe0ac9b68dfc161a4c079b695a320a0e133...master

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openjdk · 2025-07-11T18:47:52Z

@naotoj The following labels will be automatically applied to this pull request:

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mlbridge · 2025-07-11T18:54:46Z

Webrevs

test/jdk/java/io/Console/LocaleTest.java

Co-authored-by: Andrey Turbanov <[email protected]>

justin-curtis-lu · 2025-07-14T17:57:22Z

test/jdk/java/io/Console/DefaultCharsetTest.java

+    @ValueSource(strings = {"UTF-8", "ISO-8859-1", "US-ASCII", "foo", ""})
+    void testDefaultCharset(String stdoutEncoding) throws Exception {
+        // check "expect" command availability
+        var expect = Paths.get("/usr/bin/expect");


We only need to check "expect" availability once, so we should move this check to a @BeforeAll static method. It's also more clear that this check is a precondition, and not part of the actual test. Applies to the other locations, but primarily the other parameterized tests.

Good point. Modified to use @BeforeAll. For ModuleSelectionTest, one of the test is not using expect, so I left it as it is. In addition to that, I removed the @requires condition to allow that test to run on windows.

justin-curtis-lu · 2025-07-14T18:29:43Z

test/jdk/java/io/Console/ModuleSelectionTest.java

+
+    @ParameterizedTest
+    @MethodSource("options")
+    void testWithoutExpect(String opts, String expected) throws Exception {


expected param looks unused.

justin-curtis-lu · 2025-07-14T18:37:56Z

test/jdk/java/io/Console/ModuleSelectionTest.java

+
+    @ParameterizedTest
+    @MethodSource("options")
+    void testWithExpect(String opts, String expected) throws Exception {


I think it would be more clear if these tests were renamed to expectConsoleTest and noConsoleTest or something along those lines.

Yeah, using expect command with junit's expect is confusing 🙂. Just renamed those methods using TTY/NonTTY, as"expect/noConsoleTest" reads somewhat odd as it includes the expected results in the test name.

justin-curtis-lu · 2025-07-14T18:40:04Z

test/jdk/java/io/Console/ModuleSelectionTest.java

+ * @requires (os.family == "linux") | (os.family == "mac")
+ * @library /test/lib
+ * @build jdk.test.lib.Utils
+ *        jdk.test.lib.JDKToolFinder


Is jdk.test.lib.JDKToolFinder needed?

lahodaj

Looks good to me, although additional review from core libs might be desirable. Thanks!

AlanBateman · 2025-07-15T13:25:16Z

src/java.base/share/classes/java/lang/System.java

     * with the current Java virtual machine, if any.
     *
     * @return  The system console, if any, otherwise {@code null}.
+     * @see Console


The method declaration already links to Console so I don't think we need another link in the "See also" section.

Maybe I missed it, but do we have anything to make it clear that it returns null if either stdin or stdout are redirected?

we do have wordings like " If the virtual machine is started from an interactive command line without redirecting the standard input AND output streams then its console will exist ..." and "If no console device is
available then an invocation of that method will return null" from the very beginning. not very "straightforward" but i think it's clear enough?

I think adding @see tag would be more helpful.

As to the spec wording wrt stdin/out, there is another issue filed to make it clearer: JDK-8361972. This PR addresses the implementation part only so that it can be backported to prior LTSes without spec change.

It already links to Console so I don't think think the additional @see is needed. Look at the generated javadoc and see what you think.

bridgekeeper · 2025-08-12T18:30:44Z

@naotoj This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

naotoj · 2025-08-12T18:33:20Z

/keepalive

openjdk · 2025-08-12T18:35:38Z

@naotoj The pull request is being re-evaluated and the inactivity timeout has been reset.

mlbridge · 2025-08-21T05:55:45Z

Mailing list message from ecki on core-libs-dev:

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stuart-marks · 2025-08-21T18:44:22Z

ecki wrote:

I know my View of console is always a bit controversial, but having access to /dev/tty despite a program have redirected stdout and stderr would be a feature, not something you actively need to disable.
But I guess writing system tools it not something Java ever was made for :)

[extracted from HTML and edited slightly by me]

There is as usual a bunch of history here. The Java Console class doesn't use /dev/tty at all. In retrospect it might have been preferable for it to have used /dev/tty from the beginning, at least on Unix. However, that's not the case; it's always been a wrapper around the combination of stdin and stdout. Having to support equivalent functions on Windows might have played a part in this design. In any case, since its introduction in JDK 1.6, Console has been based on stdin and stdout and not /dev/tty.

The question then arises as to what should happen if one or both of stdin or stdout have been redirected. Historically, if either were redirected, System.console() would return null, meaning that "the console does not exist." More recently, we introduced the JLine console provider in order to provide line editing. Unfortunately this confused the situation, as it would provide a non-null Console instance in certain cases even if stdin or stdout were redirected, leading to confused and inconsistent behavior. That's what this PR is fixing.

There's still a broader question of, could Console use /dev/tty? Calling System.console() to obtain a Console instance might open /dev/tty directly. This could work even if all of stdin, stdout, and stderr are redirected. And it could provide a full set of features (including no-echo when reading passwords, and line editing) even in this case. This could be quite useful. However, this would be an incompatbile behavior change. Given the history of Console, there are programs out there that assume that it is based around stdin and stdout and mix operations on them. However, it might be possible to create a Console based on /dev/tty, and applications that are prepared for this change could opt into using this implementation. There are also questions about how this would work on Windows.

naotoj · 2025-08-22T17:48:27Z

Thanks for the reviews!
/integrate

openjdk · 2025-08-22T17:50:26Z

Going to push as commit ae0dac4.
Since your change was applied there have been 509 commits pushed to the master branch:

1988222: 8365829: Multiple definitions of static 'phase_names'
e916ce8: 8365878: jshell TOOLING's javap should use binary names
dba0d54: 8365832: Optimize FloatingDecimal and DigitList with byte[] and cleanup
... and 506 more: https://git.openjdk.org/jdk/compare/3d74cbe0ac9b68dfc161a4c079b695a320a0e133...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-08-22T17:50:34Z

@naotoj Pushed as commit ae0dac4.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

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Co-authored-by: Andrey Turbanov <[email protected]>

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8361613: System.console() should only be available for interactive terminal #26273

8361613: System.console() should only be available for interactive terminal #26273

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