stdbuf: use exec instead of forking #9495

Ecordonnier · 2025-11-26T23:04:13Z

forking creates a new PID and it not compatible with GNU coreutils implementation.

use Command::exec() instead of Command::spawn() which forks
add stdbuf test verifying that no fork happens

github-actions · 2025-11-26T23:18:55Z

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

github-actions · 2025-12-01T13:51:20Z

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

codspeed-hq · 2025-12-03T13:07:37Z

Merging this PR will not alter performance

✅ 141 untouched benchmarks
⏩ 38 skipped benchmarks¹

_{Comparing Ecordonnier:eco/stdbuf-exec-instead-of-fork (548a5e9) with main (0d403a4)}

38 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

github-actions · 2025-12-03T13:10:39Z

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

github-actions · 2025-12-03T13:35:59Z

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

Ecordonnier · 2025-12-03T14:53:49Z

This is ready for review. I don't intend to work on this branch any more.

Ecordonnier · 2025-12-09T00:03:21Z

I've just seen #9013 (comment) which is also relevant for my PR. I'll check if Command::exec() can be used instead of Command::status().

github-actions · 2025-12-09T10:43:05Z

GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

github-actions · 2025-12-09T11:30:40Z

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

Ecordonnier · 2025-12-09T12:23:18Z

The PR is ready for review.

github-actions · 2025-12-09T21:13:12Z

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

github-actions · 2025-12-09T21:40:10Z

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

github-actions · 2025-12-10T10:02:18Z

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

github-actions · 2025-12-17T09:53:51Z

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/inotify-dir-recreate is now passing!

github-actions · 2026-01-06T17:46:22Z

GNU testsuite comparison:

GNU test failed: tests/shuf/shuf-reservoir. tests/shuf/shuf-reservoir is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/sort/sort-stale-thread-mem. tests/sort/sort-stale-thread-mem is passing on 'main'. Maybe you have to rebase?

Forking creates a new PID and it not compatible with GNU coreutils implementation. - use exec instead of forking - add test verifying that execvp is used Fixes uutils#9066 Signed-off-by: Etienne Cordonnier <[email protected]>

github-actions · 2026-01-06T21:35:26Z

GNU testsuite comparison:

Congrats! The gnu test tests/shuf/shuf-reservoir is no longer failing!
Congrats! The gnu test tests/sort/sort-stale-thread-mem is no longer failing!

Copilot

Pull request overview

This PR replaces the fork+spawn implementation in stdbuf with a direct exec() call, making it compatible with GNU coreutils. The previous implementation broke signal handling and PR_SET_PDEATHSIG because it created a new PID through forking. With exec(), the stdbuf process is replaced by the target command, preserving the PID and allowing signals to propagate correctly.

Changes:

Replaced Command::spawn() with Command::exec() to avoid forking
Simplified error handling by removing wait/signal logic (no longer needed with exec)
Added comprehensive test to verify no fork occurs by checking /proc cmdline

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/uu/stdbuf/src/stdbuf.rs	Replaces spawn+wait with exec, updates imports, simplifies error handling to match exec-only flow
tests/by-util/test_stdbuf.rs	Adds Linux-specific regression test that validates exec behavior by polling /proc to ensure process replacement occurs

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

src/uu/stdbuf/src/stdbuf.rs

Co-authored-by: Copilot <[email protected]>

Ecordonnier · 2026-01-14T15:23:18Z

@cakebaker can you please review this PR?

This comment was marked as resolved.

Sign in to view

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from de2b66c to 0110357 Compare December 1, 2025 12:50

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from 0d7529b to 4c557bf Compare December 3, 2025 13:21

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from 4c557bf to 9afe842 Compare December 9, 2025 10:27

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from 9afe842 to af3957e Compare December 9, 2025 11:13

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from af3957e to 197203c Compare December 9, 2025 20:54

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from 197203c to 8ae82a8 Compare December 9, 2025 21:23

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from 8ae82a8 to 11a9c80 Compare December 10, 2025 09:46

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from 11a9c80 to 7963769 Compare December 17, 2025 09:35

ChrisDryden mentioned this pull request Dec 19, 2025

GNU coreutils 9.9: Detailed Test report 12/19 #9729

Open

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from 8534afe to 964753c Compare January 6, 2026 17:27

stdbuf: use exec instead of forking

a235f1a

Forking creates a new PID and it not compatible with GNU coreutils implementation. - use exec instead of forking - add test verifying that execvp is used Fixes uutils#9066 Signed-off-by: Etienne Cordonnier <[email protected]>

Ecordonnier force-pushed the eco/stdbuf-exec-instead-of-fork branch from 964753c to a235f1a Compare January 6, 2026 21:24

Ecordonnier requested a review from Copilot January 11, 2026 20:18

Copilot started reviewing on behalf of Ecordonnier January 11, 2026 20:18 View session

Copilot AI reviewed Jan 11, 2026

View reviewed changes

src/uu/stdbuf/src/stdbuf.rs Show resolved Hide resolved

Update src/uu/stdbuf/src/stdbuf.rs

548a5e9

Co-authored-by: Copilot <[email protected]>

This comment was marked as resolved.

Sign in to view

sylvestre merged commit c66be8c into uutils:main Jan 17, 2026
132 checks passed

Ecordonnier deleted the eco/stdbuf-exec-instead-of-fork branch January 17, 2026 09:32

Uh oh!

stdbuf: use exec instead of forking #9495

stdbuf: use exec instead of forking #9495

Conversation

Ecordonnier commented Nov 26, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions bot commented Nov 26, 2025

Uh oh!

This comment was marked as resolved.

This comment was marked as resolved.

github-actions bot commented Dec 1, 2025

Uh oh!

codspeed-hq bot commented Dec 3, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Merging this PR will not alter performance

Footnotes

Uh oh!

github-actions bot commented Dec 3, 2025

Uh oh!

github-actions bot commented Dec 3, 2025

Uh oh!

Ecordonnier commented Dec 3, 2025

Uh oh!

Ecordonnier commented Dec 9, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions bot commented Dec 9, 2025

Uh oh!

github-actions bot commented Dec 9, 2025

Uh oh!

Ecordonnier commented Dec 9, 2025

Uh oh!

github-actions bot commented Dec 9, 2025

Uh oh!

github-actions bot commented Dec 9, 2025

Uh oh!

github-actions bot commented Dec 10, 2025

Uh oh!

github-actions bot commented Dec 17, 2025

Uh oh!

github-actions bot commented Jan 6, 2026

Uh oh!

github-actions bot commented Jan 6, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Ecordonnier commented Jan 14, 2026

Uh oh!

This comment was marked as resolved.

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Ecordonnier commented Nov 26, 2025 •

edited

Loading

codspeed-hq bot commented Dec 3, 2025 •

edited

Loading

Ecordonnier commented Dec 9, 2025 •

edited

Loading