clearerr · shipping · also clearerr(), clearerr(3)

clearerr

clearerr is a C standard-I/O operation that clears a stream's error and end-of-file indicators.

Related Observatory article: clearerr on hesela.com

The function returns no value. With a valid stream it does not change errno; clearing stream indicators is separate from resetting that variable. [1]

This is a status operation, not an output replay, a file synchronization request or a repair protocol. The pinned glibc implementation locks the stream, clears its indicators and unlocks it. Preserve the original failure before resetting state, and decide separately how the application will recover. [2]

In Hesela's cross-libc probe, clearerr changed the recorded error indicator from set to clear after failed output. The underlying sink was still /dev/full, which rejects writes with ENOSPC. A cleared flag therefore did not mean that output had reached storage or that the failing condition had disappeared. [4] [3]

Relations

related

ferror, fwrite, fflush, fclose, fsync

Limitations

• Clearing indicators does not repair failed output or prove persistence.

Citations

1. Linux man-pages: ferror(3), clearerr(3) and errno (accessed 2026-10-21)
2. glibc 2.39: clearerr implementation (accessed 2026-10-21)
3. Linux man-pages: full(4), a device that rejects writes (accessed 2026-10-21)
4. Hesela: cross-libc fwrite observations and stream error history (accessed 2026-10-21)

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