Plan log file rotation

Easy~12 min

A directory holds app.log, app.log.1, app.log.2, … (higher number = older). Rotating keeps at most keep rotated files:

Delete every rotated file whose number would exceed keep after shifting (number ≥ keep).
Rename app.log.N to app.log.N+1, from the highest N down to 1 (so nothing is overwritten).
Rename app.log to app.log.1.

Given the list of existing file names (any order) and keep, return the list of operations in the order they must run: ["delete", name] or ["rename", old, new]. Ignore files that don't belong to the log.

Function

Implement rotation_plan. Input: files: list[str], base: str, keep: int. Returns: list[list[str]].

Constraints

keep >= 1

Examples

>>> rotation_plan(['app.log', 'app.log.1', 'app.log.2', 'other.txt'], 'app.log', 2)

[['delete', 'app.log.2'], ['rename', 'app.log.1', 'app.log.2'], ['rename', 'app.log', 'app.log.1']]

Details

Level: Functions, collections, parsing and straightforward scripting with a few edge cases.
Roles: Automation Engineer, DevOps Engineer, Site Reliability Engineer
Topics: Files and configuration, Lists and tuples
Tests: 1 public (run with Run), 3 hidden (graded on Submit)
Grading: Exact match of the return value

A directory holds app.log, app.log.1, app.log.2, … (higher number = older). Rotating keeps at most keep rotated files:

Delete every rotated file whose number would exceed keep after shifting (number ≥ keep).
Rename app.log.N to app.log.N+1, from the highest N down to 1 (so nothing is overwritten).
Rename app.log to app.log.1.

Function

Implement rotation_plan. Input: files: list[str], base: str, keep: int. Returns: list[list[str]].

Constraints

keep >= 1

Examples

>>> rotation_plan(['app.log', 'app.log.1', 'app.log.2', 'other.txt'], 'app.log', 2)

[['delete', 'app.log.2'], ['rename', 'app.log.1', 'app.log.2'], ['rename', 'app.log', 'app.log.1']]

Details

Level: Functions, collections, parsing and straightforward scripting with a few edge cases.
Roles: Automation Engineer, DevOps Engineer, Site Reliability Engineer
Topics: Files and configuration, Lists and tuples
Tests: 1 public (run with Run), 3 hidden (graded on Submit)
Grading: Exact match of the return value

Python 3.13

def rotation_plan(files: list[str], base: str, keep: int) -> list[list[str]]:
    return []

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Plan log file rotation · Python practice