Claude Sonnet 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` in the working directory and made it executable. I ran it against a scratch directory, and the behaviour matched the spec in every case I tried. I only tested one real-timestamp dry run, and `--keep=N` was not tested.\n\n- **Rotation:** four backups with `--keep 3` left the three newest, and `other.txt` in `DEST_DIR` was untouched. A dry run with `--keep 2` printed one `CREATE` and two `DELETE` lines and changed nothing.\n- **Archive contents:** a source tree with spaces in names, a `*.tmp` file and `.cache` directories at two depths archived as `./a b/f 1` and `./keep` only, with none of the excluded items.\n- **Exit codes:** `--keep 0` and an unknown option exited 2, and a missing source directory exited 3. `--help` printed usage and exited 0.\n\nBehaviours to know about:\n- **Date stamp:** an invalid `BACKUP_NOW` is treated as a usage error (exit 2).\n- **Backup name match:** retention only counts and deletes names where the timestamp parts are digits. A file like `backup-aaaaaaaa-bbbbbb.tar.gz` is never deleted, which is slightly stricter than the literal `?` pattern.\n- **Same-name backup:** if a backup with the same name already exists, it is overwritten.\n- **Older-than-keep stamp:** if `BACKUP_NOW` is older than the kept backups, the new archive is created and then deleted straight away. A dry run shows both lines.\n- **Exclusion scope:** `*.tmp` also excludes any directory whose name ends in `.tmp`.\n- **Safe writes:** the archive is written to a temporary file in `DEST_DIR` and renamed into place, so a failed run leaves no partial backup.\n- **Nested `DEST_DIR`:** if `DEST_DIR` is inside `SRC_DIR`, it is excluded from the archive.",
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