version: 1
id: linux-pipelines
title: Log Pipelines and Redirection
summary: Use pipes, redirection, and filters to turn noisy application logs into an actionable incident summary.
difficulty: beginner
estimatedMinutes: 25
prerequisites: [linux-navigation]
image: alpine:3.21
shell: /bin/sh
setup:
  - "mkdir -p /workspace/logs"
  - "printf 'ERROR payment timeout user=42\nINFO health ok\nERROR payment timeout user=7\nWARN disk 81%%\nERROR db connection reset\n' > /workspace/logs/app.log"
tasks:
  - id: filter-errors
    title: Extract and count errors
    description: Create /workspace/error-report.txt containing only ERROR lines from app.log, then write the error count to /workspace/error-count.txt.
    hints:
      - grep supports fixed-string and extended regex modes.
      - wc -l counts lines; redirect with >.
    checks:
      - type: file
        name: Error report exists
        path: /workspace/error-report.txt
        value: ERROR
      - type: command
        name: Report has three errors
        command: test "$(wc -l < /workspace/error-report.txt)" -eq 3
      - type: file
        name: Error count recorded
        path: /workspace/error-count.txt
        value: "3"
limits: {cpus: "0.5", memory: 128m, pids: 64, timeout: 1800, network: false}