Why is my Go `reader.ReadString` function not correctly processing user input?

Troubleshooting "reader.ReadString" in Go

In Go, bufio.Reader provides the ReadString method to read a line of input from a stream, stopping at a specified delimiter character. However, when using this method to retrieve user input, it can sometimes be observed that the first occurrence of the delimiter is not stripped from the returned string.

Consider the following code:

package main

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

func main() {
    reader := bufio.NewReader(os.Stdin)
    fmt.Print("Who are you? \nEnter your name: ")
    text, _ := reader.ReadString('\n')
    if aliceOrBob(text) {
        fmt.Printf("Hello, ", text)
    } else {
        fmt.Printf("You're not allowed in here! Get OUT!!")
    }
}

func aliceOrBob(text string) bool {
    if text == "Alice" {
        return true
    } else if text == "Bob" {
        return true
    } else {
        return false
    }
}

When this program runs, it prompts the user to enter their name, but even if the user enters "Alice" or "Bob", the program incorrectly prints "You're not allowed in here! Get OUT!!".

The problem lies in the fact that the ReadString method reads the line of input until the specified delimiter is encountered. However, in its default behavior, it does not remove the delimiter from the returned string. This means that when the user enters "Alice", the value of text will actually be "Alicen", which does not match any of the names in the aliceOrBob function.

To fix this, one can either use strings.TrimSpace to remove the newline character from text before checking it in the aliceOrBob function:

import (
    ....
    "strings"
    ....
)

...
if aliceOrBob(strings.TrimSpace(text)) {
...

Alternatively, one can use the ReadLine method instead of ReadString to read a line of input from os.Stdin. ReadLine returns a byte slice representing the line, without the newline character. However, since aliceOrBob expects a string, one will need to convert the byte slice to a string using the string function:

...
text, _, _ := reader.ReadLine()
if aliceOrBob(string(text)) {
...

The above is the detailed content of Why is my Go `reader.ReadString` function not correctly processing user input?. For more information, please follow other related articles on the PHP Chinese website!