fix: reject multiple patterns when -P/--perl-regexp is used - #40
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sylvestre merged 1 commit intoJun 5, 2026
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GNU grep's PCRE backend supports only a single pattern. Supplying
multiple patterns via repeated -e flags, or a pattern string that
contains a literal newline, must exit 2 with the message:
the -P option only supports a single pattern
Add the validation immediately after patterns are collected, before
regex-mode selection. Add a test covering:
- two separate -e flags with -P
- a newline-embedded pattern string with -P
- single -e with -P still works normally
Closes uutils#34
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Pull request overview
Note
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Adds GNU grep–compatible behavior for PCRE mode (-P) by rejecting multiple patterns and validating it via new regression tests.
Changes:
- Add a new test ensuring
-Pfails with exit code 2 when given multiple patterns. - Add runtime validation in
uumainto reject multiple patterns when-Pis active.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.
| File | Description |
|---|---|
| tests/test_grep.rs | Adds a regression test covering -P single-pattern restriction and expected error output. |
| src/lib.rs | Enforces “single pattern only” behavior for PCRE mode by returning exit code 2 with a specific message. |
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| // GNU grep's PCRE backend (-P) supports only a single pattern. | ||
| if perl_regexp && patterns.len() > 1 { | ||
| return Err(USimpleError::new( | ||
| 2, | ||
| "the -P option only supports a single pattern".to_string(), | ||
| )); | ||
| } |
| c.args(&["-P", "-e", "foo", "-e", "bar"]) | ||
| .pipe_in("foo\nbar\n") | ||
| .fails_with_code(2) | ||
| .stderr_contains("the -P option only supports a single pattern"); |
| c.args(&["-P", "-e", "foo\nbar"]) | ||
| .pipe_in("foo\nbar\n") | ||
| .fails_with_code(2) | ||
| .stderr_contains("the -P option only supports a single pattern"); |
| if perl_regexp && patterns.len() > 1 { | ||
| return Err(USimpleError::new( | ||
| 2, | ||
| "the -P option only supports a single pattern".to_string(), |
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Closes #34
Problem
GNU grep rejects multiple patterns when `-P` (PCRE mode) is used:
```
$ grep -P -e foo -e bar file
grep: the -P option only supports a single pattern
```
`uu_grep` was silently accepting multiple patterns and searching for all of them, diverging from GNU grep's behaviour.
Fix
Added a validation check after patterns are collected (in `src/lib.rs`) — if `--perl-regexp` is set and more than one pattern was accumulated (from multiple `-e` flags or a newline-embedded pattern string), return exit code `2` with the canonical error message.
Tests
Three cases added to `tests/test_grep.rs::perl_regexp_rejects_multiple_patterns`:
All tests pass (`cargo test perl_regexp_rejects_multiple_patterns`).