可以在Go中使用类似“ freopen”的构造吗？

Question

In C++ there's a freopen func, which is very useful to r/w files with just stdin/out(cin/cout). So I decided to find similar solution in Go, but found only

import "os"
os.Stdin, err = os.OpenFile("input.txt",
    os.RDONLY | os.O_CREATE, 0666)
os.Stdout, err = os.OpenFile("output.txt",
    os.O_WRONLY | os.O_CREATE | os.O_TRUNC, 0666)

, which is not working anymore! Am I wrong? So, do you know other way?

Answer 1

You cannot declare and assign to a variable in another package (os.Stdin, for example).

However this works:

package main

import (
    "fmt"
    "log"
    "os"
)

func main() {
    stdin, err := os.OpenFile("input.txt",
        os.O_RDONLY|os.O_CREATE, 0666)
    if err != nil {
        log.Fatal(err)
    }
    os.Stdin = stdin

    stdout, err := os.OpenFile("output.txt",
        os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
    if err != nil {
        log.Fatal(err)
    }
    os.Stdout = stdout

    fmt.Println("out")
    return
}