[gabrielhnf]

Fixes #11993

Problem

When running tail on multiple files and redirecting output to a full device (e.g. /dev/full), uutils panics instead of exiting gracefully:

thread 'main' panicked at …/std/src/io/stdio.rs:1165:9:
failed printing to stdout: No space left on device (os error 28)

Instead of the correct GNU behavior:

tail: write error: No space left on device

Cause

HeaderPrinter::print used println! to write the ==> file <== headers to stdout. println! panics on write failure rather than returning a Result, so any write error (such as ENOSPC from /dev/full) caused an unhandled panic instead of a clean error message.

Fix

Replaced println! in HeaderPrinter with write_all and flush on a locked stdout, both of which return io::Result. The methods now return io::Result and propagate write errors upstream instead of panicking.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/expand/bounded-memory is now passing!
Congrats! The gnu test tests/printf/printf-surprise is now passing!

[gabrielhnf]

Accidentally force-pushed the wrong commit onto the PR branch for a few minutes. I’ve restored the branch to the correct state now, sorry about the noise.

[codspeed]

Merging this PR will degrade performance by 19.55%

❌ 1 regressed benchmark
✅ 316 untouched benchmarks
⏩ 46 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Memory	cp_recursive_deep_tree[(120, 4)]	562.5 KB	699.2 KB	-19.55%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing gabrielhnf:fix-tail-header-write-error (b9d2a4a) with main (6a942ba)}

Footnotes

1. 46 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. ↩

[sylvestre]

why format! + write_all + flush? writeln!(stdout().lock(), ...)? should be enough, and it would avoid the allocation (codspeed shows a memory regression)

[sylvestre]

do we need this flush? stdout is line buffered anyway

[sylvestre]

please don't depend on /etc/hosts, create two files with at.write() instead

[gabrielhnf]

Hi @sylvestre! I've updated the PR and addressed your review comments:

• Replaced the format! + write_all approach with writeln!(stdout().lock(), ...)?.
• Removed the unnecessary explicit flush().
• Updated the regression test to create its own files using at.write() instead of relying on /etc/hosts.

The changes are pushed, and CI is green.

Thanks for the review!

[sylvestre]

Thanks for your PR