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How to read from standard input in the console?


Question

I would like to read standard input from the command line, but my attempts have ended with the program exiting before I'm prompted for input. I'm looking for the equivalent of Console.ReadLine() in C#.

This is what I currently have:

package main

import (
    "bufio"
    "fmt"
    "os"
)

func main() {
    reader := bufio.NewReader(os.Stdin)
    fmt.Print("Enter text: ")
    text, _ := reader.ReadString('\n')
    fmt.Println(text)

    fmt.Println("Enter text: ")
    text2 := ""
    fmt.Scanln(text2)
    fmt.Println(text2)

    ln := ""
    fmt.Sscanln("%v", ln)
    fmt.Println(ln)
}
2019/09/24
1
278
9/24/2019 11:25:10 AM

Accepted Answer

I'm not sure what's wrong with the block

reader := bufio.NewReader(os.Stdin)
fmt.Print("Enter text: ")
text, _ := reader.ReadString('\n')
fmt.Println(text)

As it works on my machine. However, for the next block you need a pointer to the variables you're assigning the input to. Try replacing fmt.Scanln(text2) with fmt.Scanln(&text2). Don't use Sscanln, because it parses a string already in memory instead of from stdin. If you want to do something like what you were trying to do, replace it with fmt.Scanf("%s", &ln)

If this still doesn't work, your culprit might be some weird system settings or a buggy IDE.

2014/01/03
312
1/3/2014 2:59:47 AM

you can as well try:

scanner := bufio.NewScanner(os.Stdin)
for scanner.Scan() {
    fmt.Println(scanner.Text())
}

if scanner.Err() != nil {
    // handle error.
}
2017/10/18

I think a more standard way to do this would be:

package main

import "fmt"

func main() {
    fmt.Print("Enter text: ")
    var input string
    fmt.Scanln(&input)
    fmt.Print(input)
}

Take a look at the scan godoc: http://godoc.org/fmt#Scan

Scan scans text read from standard input, storing successive space-separated values into successive arguments. Newlines count as space.

Scanln is similar to Scan, but stops scanning at a newline and after the final item there must be a newline or EOF.

2020/06/20

Always try to use the bufio.NewScanner for collecting input from the console. As others mentioned, there are multiple ways to do the job but Scanner is originally intended to do the job. Dave Cheney explains why you should use Scanner instead of bufio.Reader's ReadLine.

https://twitter.com/davecheney/status/604837853344989184?lang=en

Here is the code snippet answer for your question

package main

import (
    "bufio"
    "fmt"
    "os"
)

/*
 Three ways of taking input
   1. fmt.Scanln(&input)
   2. reader.ReadString()
   3. scanner.Scan()

   Here we recommend using bufio.NewScanner
*/

func main() {
    // To create dynamic array
    arr := make([]string, 0)
    scanner := bufio.NewScanner(os.Stdin)
    for {
        fmt.Print("Enter Text: ")
        // Scans a line from Stdin(Console)
        scanner.Scan()
        // Holds the string that scanned
        text := scanner.Text()
        if len(text) != 0 {
            fmt.Println(text)
            arr = append(arr, text)
        } else {
            break
        }

    }
    // Use collected inputs
    fmt.Println(arr)
}

If you don't want to programmatically collect the inputs, just add these lines

   scanner := bufio.NewScanner(os.Stdin)
   scanner.Scan()
   text := scanner.Text()
   fmt.Println(text)

The output of above program will be:

Enter Text: Bob
Bob
Enter Text: Alice
Alice
Enter Text:
[Bob Alice]

Above program collects the user input and saves them to an array. We can also break that flow with a special character. Scanner provides API for advanced usage like splitting using a custom function etc, scanning different types of I/O streams(Stdin, String) etc.

2018/04/08

Another way to read multiple inputs within a loop which can handle an input with spaces:

package main
import (
    "fmt"
    "bufio"
    "os"
)

func main() {
    scanner := bufio.NewScanner(os.Stdin)
    var text string
    for text != "q" {  // break the loop if text == "q"
        fmt.Print("Enter your text: ")
        scanner.Scan()
        text = scanner.Text()
        if text != "q" {
            fmt.Println("Your text was: ", text)
        }
    }
}

Output:

Enter your text: Hello world!
Your text was:  Hello world!
Enter your text: Go is awesome!
Your text was:  Go is awesome!
Enter your text: q
2016/11/20

I'm late to the party. But how about one liner:

data, err := ioutil.ReadAll(os.Stdin)

and press ctrl+d (EOT) once input is entered on command line.

2020/06/07