feat(builtins): add pr

[chaliy]

Requested by Михайло · project thread

What changed

New pr builtin, which paginates and columnates text. It supports:

• page headers with date, title and page number
• -COLUMN down or across (-a), balancing the columns on the last page
• -m merge
• -n, -N, -d, -o
• -s, -S, -J
• -l, -w, -W
• +FIRST:LAST, -D, -h, -F

Output is byte-identical to GNU pr on an 88-case differential corpus. That includes GNU's tab padding in multi-column output and its error messages. Header dates come from the sandbox clock and TZ, the same ones date uses.

Why

Step 4 of the level-up roadmap: pr was one of the missing coreutils. It was written from GNU's observable behavior, not from GNU's source, because that source is GPL and bashkit is MIT.

Before / After

Before:

$ seq 7 | pr -t -3
bash: pr: command not found

After:

$ seq 7 | pr -t -3 | cat -A
1^I^I^I4^I^I^I6$
2^I^I^I5^I^I^I7$
3$
$ seq 3 | pr -l 13 -D DATE -h TITLE

DATE                          TITLE                             Page 1

1
2
3

GNU pr prints the same bytes.

Risk

• Low
• New command. Padding can multiply the input size, so output is capped at 16 MiB and options are bounded at 10,000.
• -e and -i are not implemented (L-PR-001).
• A fuzz run of 600 random inputs and option mixes found no panics.

Checklist

• Tests added or updated (pr.test.sh with 25 cases checked against real bash, plus unit tests)
• Backward compatibility considered

https://claude.ai/code/session_019aFikmptPc91Fj4N2iDXQA

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Generated by Claude Code

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