英文:
Can't check strings.HasSuffix on string captured with reader.ReadString
问题
概述：我之前使用fmt.Scanln来捕获字符串，但我需要字符串中包含空格，所以我开始使用reader.ReadString。我需要检查字符串中是否存在后缀，以进行一些替换操作，所以我使用了strings.HasSuffix。在使用fmt.Scanln捕获的字符串中没有问题，但现在使用reader.ReadString后，无法在字符串中找到给定的后缀。
有关发生了什么的线索吗？
以下是一个隔离问题的测试代码，请在桌面安装的Go环境中使用，而不是在线环境。
package main
import (
"bufio"
"fmt"
"strings"
"os"
"reflect"
)
const TOKEN string = ":="
func validate(expr string) {
fmt.Println("var type: ", reflect.TypeOf(expr))
if strings.Contains(expr, TOKEN) {
fmt.Println(expr, "contains works")
} else {
fmt.Println("error with contains")
}
if strings.HasSuffix(expr, TOKEN) {
fmt.Println(expr, "suffix works")
} else {
fmt.Println("error with suffix")
}
}
func main() {
var expr2 string
reader := bufio.NewReader(os.Stdin)
fmt.Print("type something finished with ':='")
expr1, _ := reader.ReadString('\n')
fmt.Scanln(&expr2)
fmt.Println("validation with reader:")
validate(expr1)
fmt.Println()
fmt.Println("validation with Scanln:")
validate(expr2)
}
英文:
Overview: I was capturing strings with fmt.Scanln, but one of my needs is that the string must have spaces so I started to use reader.ReadString, I have to check the presence of a suffix in that string to make some replacing, so I used strings.HasSuffix. With strings captured with fmt.Scanln there was no problema but now that I use reader.ReadString it is unabled to find the given suffix in the string.
Is there a clue on what's going on?
Here is a test that isolate the problem, use it in desktop installed Go, not online.
package main
import (
"bufio"
"fmt"
"strings"
"os"
"reflect"
)
const TOKEN string = ":="
func validate(expr string) {
fmt.Println("var type: ", reflect.TypeOf(expr))
if strings.Contains(expr, TOKEN) {
fmt.Println(expr, "contains works")
} else {
fmt.Println("error with contains")
}
if strings.HasSuffix(expr, TOKEN) {
fmt.Println(expr, "suffix works")
} else {
fmt.Println("error with suffix")
}
}
func main() {
var expr2 string
reader := bufio.NewReader(os.Stdin)
fmt.Print("type something finished with ':='")
expr1, _ := reader.ReadString('\n')
fmt.Scanln(&expr2)
fmt.Println("validation with reader: ")
validate(expr1)
fmt.Println()
fmt.Println("validation with Scanln: ")
validate(expr2)
}
答案1
得分: 3
根据@Tim的提到，reader.ReadString('\n')的输出包括最后一个字符\n，而fmt.Scanln则不包括。你可以选择使用const TOKEN string = ":=\n"或者从字符串末尾删除\n。
更新：
有些情况下，\r\n会作为后缀出现，而不是通常期望的\n（Windows机器？）
根据fmt的godoc，fmt.Scanln也处理了这种情况。
在所有的扫描函数中，紧跟在回车符后面的换行符被视为普通的换行符（\r\n与\n的含义相同）。
英文:
As @Tim mentioned the output of reader.ReadString('\n') includes '\n' as the last character and fmt.Scanln does not do that. You can either do const TOKEN string = ":=\n" or remove the '\n' from the end of the string.
Update :
There are cases where \r\n occurs as a suffix instead of the usually expected\n (Windows Machines ?)
fmt.Scanln handles that case as well, as per fmt godoc.
In all the scanning functions, a carriage return followed immediately by a newline is treated as a plain newline (\r\n means the same as \n).
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