Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Write a robust backup rotation script (dry-run, spaces, exit codes, safe deletion)

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  "result": "I wrote `rotate.sh` and made it executable. I ran it against a scratch directory with spaces in file, folder and destination names, and everything below behaved as specified. I couldn't lint it because shellcheck isn't installed.\n\n**What the tests showed:**\n- **Archive contents:** paths inside the archive look like `./my file.txt` and `./sub dir/keep me`. `x.tmp` and every `.cache` directory were left out, at the top level and nested. Things that only look similar are kept: a file named `.cachefile` and a directory named `a.tmp.d`.\n- **Rotation:** `--keep 2` after three runs kept the two newest names. The default keeps 5 (7 runs left 5). `notes.txt` and `backup-foo.tar.gz` were never touched.\n- **Order is by the name, not by when it ran:** if you create backups out of order, the one with the oldest timestamp in its name is deleted first. That can include the backup just created, if its timestamp is the oldest.\n- **`--dry-run`:** it prints `CREATE \u2026` and then `DELETE \u2026` lines, and the directory is unchanged afterwards. It counts the backup it would create when working out what to delete. It doesn't create a missing `DEST_DIR`.\n- **Exit codes:** 2 for `--keep 0`, `--keep x`, a missing `--keep` value, an unknown option or a missing argument. 3 when `SRC_DIR` doesn't exist. 0 for `--help`, which prints to stdout.\n- **Relative paths** and a trailing `/` on `DEST_DIR` both work.\n\n**Choices I made where the spec was silent:**\n- **Failure exit code:** if tar fails, or `DEST_DIR` exists but is a file, it exits 1. This keeps tar's own exit code 2 from looking like a usage error.\n- **No half-written backups:** the archive is written to a temporary `.\u2026.tmp` file in `DEST_DIR` and renamed only when it's complete.\n- **Strict name matching:** only names with digits in the timestamp count as backups, which is narrower than the `?` pattern. A file like `backup-abcdefgh-ijklmn.tar.gz` is never deleted and doesn't count toward N.\n- **Bad `BACKUP_NOW`:** a value that isn't `YYYYMMDD-HHMMSS` is treated as a usage error (exit 2).\n- **`--keep` forms:** both `--keep=N` and `--` (end of options) are accepted.\n- **Same timestamp twice:** a second run with the same timestamp overwrites the first backup.\n- **Normal runs print nothing.**\n- **`DEST_DIR` inside `SRC_DIR`:** this works and the in-progress file isn't included. Older backups already in that folder do get included in the new archive.",
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