CmdNotify - Command Monitor Skill#

触发词#

当用户提到以下关键词时激活此技能：

• "监控命令"
• "命令告警"
• "定时执行脚本"
• "输出变化检测"
• "cmdnotify"
• "command monitor"
• "batch script execution"

使用场景#

• 批量监控多个系统命令的输出变化
• 定时执行脚本并检测异常
• 磁盘使用率、内存、进程数等系统指标监控
• API 健康检查与状态变化告警
• 配置文件漂移检测
• 日志模式监控

Overview#

CmdNotify is a lightweight, resource-optimized command monitoring system written in Go. It allows you to:

• Batch monitor multiple commands/scripts simultaneously
• Set custom execution intervals for each command
• Automatically detect output changes (stdout/stderr + exit code)
• Trigger alerts when changes are detected
• Run with minimal CPU/memory footprint using goroutine pools and timeouts

Quick Start#

1. Configuration#

Create a config.json file:

json

{
  "commands": [
    {
      "name": "disk_usage",
      "command": "df -h /",
      "interval": "30s",
      "timeout": "10s",
      "notify_on": ["change"],
      "max_history": 2
    },
    {
      "name": "memory_check",
      "command": "vm_stat | grep 'Pages free'",
      "interval": "20s",
      "timeout": "5s",
      "notify_on": ["change"],
      "notify_cmd": "echo '[ALERT] $CMD_NAME: $CMD_MESSAGE'",
      "max_history": 2
    }
  ]
}

2. Build & Run#

bash

# Build
go build -o cmdnotify .

# Run with default config
./cmdnotify

# Run with custom config
./cmdnotify -config /path/to/config.json

Configuration Options#

FieldTypeDefaultDescriptionnamestringrequiredUnique identifier for the commandcommandstringrequiredShell command to executeintervalduration1sExecution interval (e.g., 30s, 5m, 1h)timeoutduration30sMaximum execution time per runnotify_on[]string[]Events to notify on: ["change"], ["error"], ["all"]``notify_cmdstring""Custom notification command (optional)max_historyint2Number of results to keep for change detectionworking_dirstring""Working directory for command execution

Notification#

Default Behavior#

When no notify_cmd is specified, alerts are printed to stderr:

text

[disk_usage] Command 'disk_usage' output changed
Exit code: 0
Output:
Filesystem      Size   Used  Avail Capacity
/dev/disk1s1   228Gi  180Gi   48Gi    79%

Custom Notification#

Set notify_cmd to integrate with external systems:

json

{
  "notify_cmd": "curl -X POST -d '{\"text\":\"$CMD_MESSAGE\"}' https://hooks.slack.com/services/..."
}

Environment variables available in notify_cmd:

• CMD_NAME - Command name
• CMD_MESSAGE - Alert message

Resource Optimization#

CmdNotify is designed for minimal resource consumption:

FeatureImplementationGoroutine PoolSemaphore-based concurrency limiting (default: CPU count, min 4)Timeout ControlPer-command context.WithTimeout prevents zombie processesMemory Reusebytes.Buffer for output; history limited to max_historyEfficient HashingSHA-256 of output + exit code for fast change detectionGraceful Shutdowncontext.Cancel + sync.WaitGroup ensures clean exit

Project Structure#

text

CmdNotify/
├── config.go      # Configuration loading & validation
├── config.json    # Example configuration
├── executor.go    # Command execution & change detection
├── scheduler.go   # Scheduling engine with goroutine pool
├── main.go        # Entry point
└── go.mod         # Go module definition

Use Cases#

• Monitor disk usage changes
• Track process counts
• Watch log file patterns
• Check service health endpoints
• Detect configuration drift
• Monitor system resource usage

Advanced Example#

json

{
  "commands": [
    {
      "name": "api_health",
      "command": "curl -s -o /dev/null -w '%{http_code}' http://localhost:8080/health",
      "interval": "10s",
      "timeout": "5s",
      "notify_on": ["change", "error"],
      "notify_cmd": "echo '[$(date)] $CMD_NAME status changed: $CMD_MESSAGE' >> /var/log/alerts.log",
      "max_history": 3
    },
    {
      "name": "db_connection_count",
      "command": "psql -c 'SELECT count(*) FROM pg_stat_activity;' -t",
      "interval": "1m",
      "timeout": "10s",
      "notify_on": ["all"],
      "working_dir": "/opt/monitoring"
    }
  ]
}