Fixes vlang#189 and vlang#193. The old code read the random source into memory, summed the bytes, fed that to a V PRNG and shuffled with a hand written swap loop. That is not what GNU does, so the same file gave a different permutation and the test that checks it failed. src/shuf/randint.v is now a direct port of GNU's gl/lib/randint.c and gl/lib/randperm.c. The leftover entropy in randnum/randmax has to be carried across calls exactly as GNU does, because that is observable: shuf -i 1-5 over a one byte source still consumes a single byte, and only because of that carry. GNU also switches to a hash based sparse representation for large sparse permutations; that is purely a memory optimisation and performs the same swaps in the same order, so it is not reproduced here. Verified byte for byte against GNU coreutils 9.4 for -i 1-5, -i 0-99, -n 3 from 5 lines, all lines, -r -n 6 in echo/file/range mode, -o, stdin, -n larger than the input, and the end-of-file and missing-file errors. * Empty lines were dropped. `register_lines_by_file` had `if line.len > 0`, so `shuf` silently lost them. * `-z` did not work. The zero-terminated path appended the whole input as a single element instead of splitting on NUL, and `open_operands` split on newline regardless of the flag. * `-n 0` output every line instead of nothing. The old code used 0 to mean "every line", which is exactly what -n 0 is not. * `-r -n COUNT` re-shuffled for every line of output, so it could repeat the whole input COUNT times instead of picking COUNT lines. * `-i` accepted anything: `split('-')` with no validation, so `5-1`, `abc`, `1-x` and `1-2-3` were all accepted. These are now rejected the way GNU rejects them, with GNU's message. * `-e` together with `-i`, and extra operands, were accepted. Both are now rejected. * A missing input file reported V's `failed to open file "..."` rather than GNU's `No such file or directory`. The option descriptions now use GNU's wording, and the three usage lines match GNU's: ``` Usage: shuf [OPTION]... [FILE] or: shuf -e [OPTION]... [ARG]... or: shuf -i LO-HI [OPTION]... ``` The options use the `_opt` flag variants so V stops appending a "(default false)" note to each one, and the value names are LO-HI, COUNT, FILE and FILE as in GNU. The surrounding boilerplate is still the shape common.flag_parser gives every utility in this repository; reproducing GNU's exact --help layout would mean bypassing it and diverging from the rest of the tools, which the README asks for. The descriptions, which is what the issue was about, now match. test_random_source no longer hardcodes a permutation. The expectation `1 4 5 2 3` came from GNU 8.32 and does not match any current GNU: 9.4 produces `5 2 1 3 4` for the same input. The permutation for a given random source is fully determined, so the tests now compare against the platform shuf through the rig, which is what the other tests in this file already do. Added coverage for lines, -n, repeat, exhaustion, a missing source, empty lines, -z, -o, -n 0, and the input-range and operand errors. `v test .` is now 47/47, was 46/47.

Commits

Commits on Oct 3, 2026

shuf: match GNU's RNG and input handling