如何将脚本用户输入转为cron参数并实现定时ping测试结果对比

Hey there! Let's tackle your two questions with concrete, actionable steps that fit right into your workflow.

1. Replace User Input with Command-Line Arguments (for Cron) #

Instead of relying on input() to get pre/post, we can modify your script to accept command-line arguments. This makes it seamless to pass values directly from cron jobs without any manual input.

Here's the adjusted script with argument handling:

#!/usr/bin/env python3
import sys
import os

# Use absolute paths for result files (critical for cron's minimal environment)
BASE_DIR = "/var/log/router_ping_results"
PRE_RESULTS_PATH = f"{BASE_DIR}/pre_maintenance.txt"
LAST_RESULTS_PATH = f"{BASE_DIR}/last_run.txt"

def run_ping_tests():
    # Your existing ping test logic here (return dict of router: result)
    # Example mock data:
    return {
        "router_1": "SUCCESS RATE IS 0 PERCENT",
        "router_2": "SUCCESS RATE IS 100 PERCENT",
        "router_3": "SUCCESS RATE IS 50 PERCENT"
    }

def save_results(results, file_path):
    # Create directory if it doesn't exist
    os.makedirs(os.path.dirname(file_path), exist_ok=True)
    with open(file_path, "w") as f:
        for router, result in results.items():
            f.write(f"{router}:{result}\n")

def load_results(file_path):
    results = {}
    with open(file_path, "r") as f:
        for line in f:
            router, result = line.strip().split(":", 1)
            results[router] = result
    return results

def compare_results(previous, current):
    # Your comparison logic (matches your example rules)
    print("=== Comparison Results ===")
    for router in previous:
        prev_rate = previous[router].split()[-2]
        curr_rate = current[router].split()[-2]
        if prev_rate == curr_rate:
            print(f"{router}: *PASS* (Pre: {prev_rate}% | Post: {curr_rate}%)")
        else:
            print(f"{router}: *FAIL* (Pre: {prev_rate}% | Post: {curr_rate}%)")

def main():
    # Validate command-line arguments
    if len(sys.argv) != 2:
        print("Usage: ./ping_script.py [pre|post|auto]")
        sys.exit(1)
    
    mode = sys.argv[1].lower()
    if mode not in ["pre", "post", "auto"]:
        print("Error: Argument must be 'pre', 'post', or 'auto'")
        sys.exit(1)
    
    current_results = run_ping_tests()
    
    if mode == "pre":
        save_results(current_results, PRE_RESULTS_PATH)
        print("Pre-maintenance tests completed. Results saved.")
    elif mode == "post":
        if not os.path.exists(PRE_RESULTS_PATH):
            print("Error: Pre-maintenance results not found. Run 'pre' first.")
            sys.exit(1)
        pre_results = load_results(PRE_RESULTS_PATH)
        compare_results(pre_results, current_results)
    elif mode == "auto":
        # Compare against the last run's results, then save current as new last
        if os.path.exists(LAST_RESULTS_PATH):
            last_results = load_results(LAST_RESULTS_PATH)
            compare_results(last_results, current_results)
        else:
            print("No previous results found. Saving current run as baseline.")
        save_results(current_results, LAST_RESULTS_PATH)

if __name__ == "__main__":
    main()

Key improvements:

• Uses sys.argv to accept pre/post/auto directly from the command line
• Uses absolute paths for result storage (avoids cron path issues)
• Adds an auto mode for comparing against the most recent run
• Includes validation for missing arguments or results files

2. Configuring Cron Jobs for Automated Testing #

Option A: Pre/Post Maintenance Schedule #

If you have fixed maintenance windows, schedule two separate cron jobs:

1. Run pre before maintenance
2. Run post after maintenance to compare against the pre results

Step 1: Make the script executable

chmod +x /path/to/your/ping_script.py

Step 2: Edit your crontab

Open your user's crontab (use sudo crontab -e if root access is needed for ping tests):

crontab -e

Add these lines (adjust times and paths to match your schedule):

# Run pre-maintenance test at 1:00 AM on the 15th of every month
0 1 15 * * /path/to/your/ping_script.py pre >> /var/log/router_ping_results/cron_pre.log 2>&1

# Run post-maintenance comparison at 3:00 AM on the 15th of every month
0 3 15 * * /path/to/your/ping_script.py post >> /var/log/router_ping_results/cron_post.log 2>&1

• The >> /var/log/... 2>&1 redirects both output and errors to a log file (critical for debugging cron issues)
• Ensure the log directory exists and the cron user has write access:

  sudo mkdir -p /var/log/router_ping_results
  sudo chown your_username:your_username /var/log/router_ping_results
  

Option B: Auto-Compare Every X Interval #

If you want to run tests regularly and compare each run against the last one, use the auto mode:
Add this line to your crontab (runs every hour as an example):

# Run test and compare with last run every hour
0 * * * * /path/to/your/ping_script.py auto >> /var/log/router_ping_results/cron_auto.log 2>&1

Critical Cron Best Practices #

• Always use absolute paths for scripts, result files, and logs (cron doesn't inherit your user's full PATH)
• Test the script manually first with the command-line argument to confirm it works
• Check system cron logs (usually /var/log/syslog on Debian/Ubuntu) if jobs fail to run
• If ping requires elevated privileges, run the cron job with sudo crontab -e

内容的提问来源于stack exchange，提问作者Surender Reddy