doumu2172
2017-09-14 15:55 阅读 39
已采纳

Golang:fmt.Printf stdout的挂起发生在fmt.scan的for循环旁边

As title, it's hard for me to describe the problem. So I showed the sample code, input and output below.

package main

import (
    "fmt"
)

func main() {
    for i := 1; i <= 3; i++ {
        var a, b, c string
        fmt.Scan(&a)
        fmt.Scan(&b)
        fmt.Scan(&c)
        fmt.Printf("%s
", a)
    }
}

Input

a b c
d e f
g h i

Expected Output

a
d
g

However, the actual output printed "a", "d" first. Then, after pressing return (enter) key, "g" was printed. This was actual output.


Update

If I pasted whole nine characters, the third iteration was hung. However, if I merely enter character one after another, it met the expected output.

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1条回答 默认 最新

  • 已采纳
    dtwupu6414 dtwupu6414 2017-09-14 17:30

    How did you enter that input without a return (enter) ?

    If you run this interactively and actually typing in all the input I think you'll understand the reason for the output.

    You will have to:

    • Type a b c - nothing will output yet as the third Scan does not know if c is all you'll type
    • Press return (enter) - only at this point you'll see the a output
    • Do the same for the other lines

    Take a look at the doc for Scan which explains this as well:

    https://golang.org/pkg/fmt/#Scan

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