详解golang执行Linux shell命令完整场景下的使用方法

目录

• 1. 执行命令并获得输出结果
• 2. 将stdout和stderr分别处理
• 3. 异步执行命令
• 4. 执行时带上环境变量
• 5. 预先检查命令是否存在
• 6. 两个命令依次执行，管道通信
• 7. 按行读取输出内容
• 8. 获得exit code

1. 执行命令并获得输出结果

CombinedOutput()

执行程序返回 standard output and standard error

func main() {
    cmd := exec.Command("ls", "-lah")
    out, err := cmd.CombinedOutput()
    if err != nil {
        log.Fatalf("cmd.Run() failed with %s\n", err)
    }
    fmt.Printf("combined out:\n%s\n", string(out))
}

Output()

执行程序返回standard output

func main() {
    out, err := exec.Command("date").Output()
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("The date is %s\n", out)
}

2. 将stdout和stderr分别处理

用buffer接受输出

func main() {
    cmd := exec.Command("ls", "-lah")
    var stdin, stdout, stderr bytes.Buffer
    cmd.Stdin = &stdin
    cmd.Stdout = &stdout
    cmd.Stderr = &stderr
    err := cmd.Run()
    if err != nil {
        log.Fatalf("cmd.Run() failed with %s\n", err)
    }
    outStr, errStr := string(stdout.Bytes()), string(stderr.Bytes())
    fmt.Printf("out:\n%s\nerr:\n%s\n", outStr, errStr)
}

直接打印到屏幕

func main() {
    cmd := exec.Command("ls", "-lah")
    cmd.Stdout = os.Stdout
    cmd.Stderr = os.Stdout
    err := cmd.Run()
    if err != nil {
        log.Fatalf("cmd.Run() failed with %s\n", err)
    }
}

3. 异步执行命令

cmd.Run() 阻塞等待命令执行结束
cmd.Start() 不会等待命令完成

package main

import (
  "bytes"
  "fmt"
  "io"
  "log"
  "os"
  "os/exec"
)

func main() {
  var stdoutBuf, stderrBuf bytes.Buffer
  cmd := exec.Command("bash", "-c", "for i in 1 2 3 4;do echo $i;sleep 2;done")
  stdoutIn, _ := cmd.StdoutPipe()
  stderrIn, _ := cmd.StderrPipe()
  var errStdout, errStderr error
  stdout := io.MultiWriter(os.Stdout, &stdoutBuf)
  stderr := io.MultiWriter(os.Stderr, &stderrBuf)
  err := cmd.Start()
  if err != nil {
    log.Fatalf("cmd.Start() failed with '%s'\n", err)
  }
  Go func() {
    _, errStdout = io.Copy(stdout, stdoutIn)
  }()
  go func() {
    _, errStderr = io.Copy(stderr, stderrIn)
  }()
  err = cmd.Wait()
  if err != nil {
    log.Fatalf("cmd.Run() failed with %s\n", err)
  }
  if errStdout != nil || errStderr != nil {
    log.Fatal("failed to capture stdout or stderr\n")
  }
  outStr, errStr := string(stdoutBuf.Bytes()), string(stderrBuf.Bytes())
  fmt.Printf("\nout:\n%s\nerr:\n%s\n", outStr, errStr)
}

4. 执行时带上环境变量

func main() {
    cmd := exec.Command("bash", "-c", "programToExecute")
    additionalEnv := "programToExecute=ls"
    newEnv := append(os.Environ(), additionalEnv)
    cmd.Env = newEnv
    out, err := cmd.CombinedOutput()
    if err != nil {
        log.Fatalf("cmd.Run() failed with %s\n", err)
    }
    fmt.Printf("%s", out)
}

5. 预先检查命令是否存在

func checkLsExists() {
    path, err := exec.LookPath("ls")
    if err != nil {
        fmt.Printf("didn't find 'ls' executable\n")
    } else {
        fmt.Printf("'ls' executable is in '%s'\n", path)
    }
}

6. 两个命令依次执行，管道通信

func main() {
    c1 := exec.Command("ls")
    c2 := exec.Command("wc", "-l")
    r, w := io.Pipe() 
    c1.Stdout = w
    c2.Stdin = r
    var b2 bytes.Buffer
    c2.Stdout = &b2
    c1.Start()
    c2.Start()
    c1.Wait()
    w.Close()
    c2.Wait()
    io.Copy(os.Stdout, &b2)
}

或者

func main() {
    c1 := exec.Command("ls")
    c2 := exec.Command("wc", "-l")
    c2.Stdin, _ = c1.StdoutPipe()
    c2.Stdout = os.Stdout
    _ = c2.Start()
    _ = c1.Run()
    _ = c2.Wait()
}

反正下面这样是不行的

func main() {
    c := exec.Command("ls", "|", "wc", "-l")
    c.Stdout = os.Stdout
    _ = c.Run()
}

不嫌丑可以用bash -c

func main() {
    cmd := "cat /proc/cpuinfo | egrep '^model name' | uniq | awk '{print substr($0, index($0,$4))}'"
    out, err := exec.Command("bash", "-c", cmd).Output()
    if err != nil {
        fmt.Printf("Failed to execute command: %s", cmd)
    }
    fmt.Println(string(out))
}

7. 按行读取输出内容

func main() {
    cmd := exec.Command("ls", "-la")
    stdout, _ := cmd.StdoutPipe()
    cmd.Start()
    reader := bufio.NewReader(stdout)
    for {
        line, err := reader.ReadString('\n')
        line = strings.TrimSpace(line)
        if err != nil || io.EOF == err {
            break
        }
        log.Println(line)
    }
    cmd.Wait()
}

8. 获得exit code

func RunCommand(name string, args ...string) (stdout string, stderr string, exitCode int) {
  log.Println("run command:", name, args)
  var outbuf, errbuf bytes.Buffer
  cmd := exec.Command(name, args...)
  cmd.Stdout = &outbuf
  cmd.Stderr = &errbuf

  err := cmd.Run()
  stdout = outbuf.String()
  stderr = errbuf.String()

  if err != nil {
    // try to get the exit code
    if exitError, ok := err.(*exec.ExitError); ok {
      ws := exitError.Sys().(syscall.WaitStatus)
      exitCode = ws.ExitStatus()
    } else {
      // This will happen (in OSX) if `name` is not available in $PATH,
      // in this situation, exit code could not be get, and stderr will be
      // empty string very likely, so we use the default fail code, and fORMat err
      // to string and set to stderr
      log.Printf("Could not get exit code for failed program: %v, %v", name, args)
      exitCode = defaultFailedCode
      if stderr == "" {
        stderr = err.Error()
      }
    }
  } else {
    // success, exitCode should be 0 if go is ok
    ws := cmd.ProcessState.Sys().(syscall.WaitStatus)
    exitCode = ws.ExitStatus()
  }
  log.Printf("command result, stdout: %v, stderr: %v, exitCode: %v", stdout, stderr, exitCode)
  return
}

参考链接：

https://saucer-man.com/backend_development/571.html

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