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

Question

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.

Answer 1

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