is_master-go/is_master.go

package main

import (
  "fmt"
  "flag"
  "os"
  "syscall"
  "strings"
  "net"
  "regexp"
)

// Option to parse
var (
  HELP    = flag.Bool("help", false, "print the help message")
  IP      = flag.String("ip", "", "ip expected")
  FILE    = flag.String("file", "", "path file expected")
  COMMAND = flag.String("command", "", "command to execute")
  NOT     = flag.Bool("not", false, "execute the command if the ip or the file isn't present")
)

// Critical print a message and exit with code 2
func Critical(msg string) {
  fmt.Println(fmt.Sprintf("CRITICAL - %s", msg))
  os.Exit(2)
}

// Warning print a message and exit with code 1
func Warning(msg string) {
  fmt.Println(fmt.Sprintf("WARNING - %s", msg))
  os.Exit(1)
}

// Ok print a message and exit with code 0
func Ok(msg string) {
  fmt.Println(fmt.Sprintf("OK - %s", msg))
  os.Exit(0)
}

func init() {
  flag.Parse()

  if *HELP {
    flag.PrintDefaults()
    os.Exit(3)
  }

  if *IP == "" && *FILE == "" {
    Critical("Please set file or ip option")
  }

  if *COMMAND == "" {
    Critical("Please set command option")
  }
}

// fileExist return true if the file exist
func fileExist(path string) bool {
    _, err := os.Stat(*FILE)
    if err == nil {
      return true
    }

    return false
}

// ipExist return true if an interface has the ip 
func ipExist(ip string) bool {
  r := regexp.MustCompile(`^(.*)/\d{1,2}$`)

  ifaces, _ := net.Interfaces()
  for _, i := range ifaces {
      addrs, _ := i.Addrs()
      for _, addr := range addrs {
        match := r.FindSubmatch([]byte(fmt.Sprintf("%s", addr)))
        if len(match) == 0 {
          continue
        }

        if string(match[1]) == ip {
          return true
        }
      }
  }

  return false
}

func main() {
  var execute bool

  if *FILE != "" {
    execute = fileExist(*FILE)
  } else {
    execute = ipExist(*IP)
  }

  if *NOT {
    if execute {
      execute = false
    } else {
      execute = true
    }
  }

  if execute {
    Ok("I have nothing to do, i going to sleep")
  }

  command := strings.Split(*COMMAND, " ")
  syscall.Exec(command[0], command, []string{})
}