在使用管道执行 go binary 时使用 scanln

Question

我有以下代码：

package main

import "fmt"

func main() {

    if scanln_test() {

        fmt.Println("Success!")

    }

}

func scanln_test() bool {

    fmt.Print("Please type yes or no and then press enter [y/n]: ")

    var response string

    fmt.Scanln(&response)

    if response == "y" {

        return true

    } else if response == "n" {

        return false

    } else {

        return scanln_test()

    }

}

通过管道执行编译后的二进制文件时，例如：

$ echo "just-showing-how-pipe-affects-the-behavior" | ./scanln

我得到函数fmt.Print内部的无限输出。scanln_test但是，当我不通过管道执行它时，一切正常。

有没有办法解决这个问题？

UPD。当使用管道执行二进制文件时，fmt.Scanln 返回“EOF”作为错误

UPD2。上面带有 echo 的示例只是为了说明管道，但我不想在我的 go 程序中阅读此 echo 的内容。真实案例如下所示：wget -qO- http://example.com/get | sh -s "param". 我在这个下载的 shell 脚本中有执行 go 程序，我希望我的程序用 Y/N 向用户显示对话。我不确定这是否可能，所以现在我决定摆脱管道并像wget -qO- http://example.com/get | sh && go-program "param".

Answer 1

因此，您需要来自 Stdin（管道）和用户 Stdin（键盘）的并发输入：我认为您的答案是 cat 命令，请参阅：如何将初始输入通过管道传输到进程中，然后该进程将是交互式的？和：https://en.wikipedia.org/wiki/Cat_(Unix)请参阅：如何在 Go 中通过管道传输多个命令？并进行进程间通信有 3 件事需要注意：首先：检查所有错误是一个好习惯：在您的情况下：n, err := fmt.Scanln(&response)&nbsp;&nbsp;第二：您正在使用递归调用（Tail Call），这里没有必要。用简单的 for 循环替换它并查看： Go3 中的尾调用优化：最后但并非最不重要的一点：如果输入错误，您的代码将永远循环（如果编译器无法优化尾调用，则消耗堆栈）！最好限制在 3 个。例如：package mainimport "fmt"import "strings"type Input intconst (&nbsp; &nbsp; Timeout Input = iota&nbsp; &nbsp; Yes&nbsp; &nbsp; No&nbsp; &nbsp; Abort&nbsp; &nbsp; BadInput)func userInput(msg string) Input {&nbsp; &nbsp; var input string&nbsp; &nbsp; for i := 0; i < 3; i++ {&nbsp; &nbsp; &nbsp; &nbsp; fmt.Println(msg)&nbsp; &nbsp; &nbsp; &nbsp; n, err := fmt.Scanln(&input)&nbsp; &nbsp; &nbsp; &nbsp; if n > 0 {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; switch strings.ToLower(input) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; case "y":&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return Yes&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; case "n":&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return No&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; case "a":&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return Abort&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; if err != nil {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return BadInput // or panic(err)&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; return Timeout}func main() {&nbsp; &nbsp; ans := userInput("Please type Yes,No or Abort and then press enter [y/n/a]: ")&nbsp; &nbsp; fmt.Println(ans)&nbsp; &nbsp; switch ans {&nbsp; &nbsp; case Yes:&nbsp; &nbsp; &nbsp; &nbsp; fmt.Println("Yes") // do some job&nbsp; &nbsp; &nbsp; &nbsp; //...&nbsp; &nbsp; }}编辑：使用这个简单的“y/n”，您无需检查它是否是管道。即使是带有一个字节切片的简单 std Read 也很好：os.Stdin.Read(b1)查看我的管道示例：https ://stackoverflow.com/a/37334984/6169399但如果您的标准输入是管道，您可以使用：bytes, err := ioutil.ReadAll(os.Stdin)&nbsp;一次读取所有管道数据。但要小心处理错误。您可以检查标准输入是否与终端或管道相关联，然后使用适当的代码。检测它的简单方法是否是管道：package mainimport (&nbsp; &nbsp; "fmt"&nbsp; &nbsp; "os")func main() {&nbsp; &nbsp; info, err := os.Stdin.Stat()&nbsp; &nbsp; if err != nil {&nbsp; &nbsp; &nbsp; &nbsp; fmt.Println("not a pipe")&nbsp; &nbsp; } else {&nbsp; &nbsp; &nbsp; &nbsp; fmt.Println("pipe name=", info.Name(), "pipe size=", info.Size())&nbsp; &nbsp; }}全部在一个示例代码中：package mainimport (&nbsp; &nbsp; "fmt"&nbsp; &nbsp; "io/ioutil"&nbsp; &nbsp; "os"&nbsp; &nbsp; "strings")type Input intconst (&nbsp; &nbsp; Timeout Input = iota&nbsp; &nbsp; Yes&nbsp; &nbsp; No&nbsp; &nbsp; Abort&nbsp; &nbsp; BadInput)func userInput(msg string) Input {&nbsp; &nbsp; var input string&nbsp; &nbsp; for i := 0; i < 3; i++ {&nbsp; &nbsp; &nbsp; &nbsp; fmt.Println(msg)&nbsp; &nbsp; &nbsp; &nbsp; n, err := fmt.Scanln(&input)&nbsp; &nbsp; &nbsp; &nbsp; if n > 0 {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; switch strings.ToLower(input) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; case "y":&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return Yes&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; case "n":&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return No&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; case "a":&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return Abort&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; if err != nil {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return BadInput // or panic(err)&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; return Timeout}func main() {&nbsp; &nbsp; info, err := os.Stdin.Stat()&nbsp; &nbsp; if err != nil {&nbsp; &nbsp; &nbsp; &nbsp; //fmt.Println("not a pipe")&nbsp; &nbsp; &nbsp; &nbsp; ans := userInput("Please type Yes,No or Abort and then press enter [y/n/a]: ")&nbsp; &nbsp; &nbsp; &nbsp; fmt.Println(ans)&nbsp; &nbsp; &nbsp; &nbsp; switch ans {&nbsp; &nbsp; &nbsp; &nbsp; case Yes:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; fmt.Println("Yes") // do some job&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; //...&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; } else {&nbsp; &nbsp; &nbsp; &nbsp; fmt.Println("pipe name=", info.Name(), "pipe size=", info.Size())&nbsp; &nbsp; &nbsp; &nbsp; bytes, err := ioutil.ReadAll(os.Stdin)&nbsp; &nbsp; &nbsp; &nbsp; fmt.Println(string(bytes), err) //do some jobe with bytes&nbsp; &nbsp; }}

Answer 2

您可以使用os.ModeCharDevice：stat, _ := os.Stdin.Stat()if (stat.Mode() & os.ModeCharDevice) == 0 {&nbsp; &nbsp; // piped&nbsp; &nbsp; input, _ := ioutil.ReadAll(os.Stdin)} else {&nbsp; &nbsp; // not piped, do whatever, like fmt.Scanln()}