Cmdnotify

Lightweight command monitoring tool that periodically executes local commands/scripts in batches, detects output changes, and triggers alerts. Built with Go for minimal resource consumption.

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:

{
  "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

# Build
go build -o cmdnotify .

# Run with default config
./cmdnotify

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

Configuration Options

Field	Type	Default	Description
name	string	required	Unique identifier for the command
command	string	required	Shell command to execute
interval	duration	1s	Execution interval (e.g., 30s, 5m, 1h)
timeout	duration	30s	Maximum execution time per run
notify_on	[]string	[]	Events to notify on: ["change"], ["error"], ["all"]
notify_cmd	string	""	Custom notification command (optional)
max_history	int	2	Number of results to keep for change detection
working_dir	string	""	Working directory for command execution

Notification

Default Behavior

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

[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:

{
  "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:

Feature	Implementation
Goroutine Pool	Semaphore-based concurrency limiting (default: CPU count, min 4)
Timeout Control	Per-command context.WithTimeout prevents zombie processes
Memory Reuse	bytes.Buffer for output; history limited to max_history
Efficient Hashing	SHA-256 of output + exit code for fast change detection
Graceful Shutdown	context.Cancel + sync.WaitGroup ensures clean exit

Project Structure

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

{
  "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"
    }
  ]
}