cut: fix -s flag ignored when delimiter is newline #10037
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When using newline as the delimiter (-d $'\n') with -s (only-delimited), cut should suppress lines that do not contain the delimiter. However, cut_fields_newline_char_delim() was not checking the only_delimited flag, causing it to always output even when -s was specified. The fix uses read_until() instead of split() to read segments. Unlike split(), read_until() includes the delimiter in the buffer when found, allowing us to detect whether a delimiter was actually present or if we just hit EOF. This commit: - Adds only_delimited parameter to cut_fields_newline_char_delim() - Uses read_until() to detect delimiter presence while reading - If no delimiter found and only_delimited is true, returns early - Adds test case for newline delimiter with -s flag Fixes uutils#10012
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sylvestre
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Jan 4, 2026
sylvestre
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- Use read_to_end + split instead of read_until loop - Use Vec<&[u8]> instead of Vec<Vec<u8>> (no extra allocations) - Rename found_delimiter to has_delimiter - Check has_delimiter before removing trailing empty segment - Only write trailing newline if we output something - Remove unused BufRead import - Add tests for edge cases: just newline, empty input
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sylvestre
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Jan 6, 2026
sylvestre
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Jan 6, 2026
Address PR review comments: - Replace read_to_end() with streaming DelimReader iterator - DelimReader uses read_until() and tracks delimiter per segment - Only collect selected fields, not entire input - Remove b"".as_slice() check (DelimReader doesn't create trailing empties) - Simplify output with split_first() join pattern
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Merging this PR will improve performance by 4.09%Summary
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When using newline as the delimiter (
-d $'\n') with-s(only-delimited), cut should suppress lines that do not contain the delimiter. However,cut_fields_newline_char_delim()was not checking theonly_delimitedflag, causing it to always output even when-swas specified.The Bug
Changes
only_delimitedparameter tocut_fields_newline_char_delim()only_delimitedis true, returns early without output-sflagFixes #10012