英文:
Golang types in net package
问题
我正在使用golang编写一些工具来使我的生活更轻松，但我完全不理解net包中的类型是如何工作的。这是我的一部分代码：
import (
"bufio"
"fmt"
"log"
"net"
"os"
)
type configFile struct {
gateway, net net.IP
mask, port int
telnetUser, telnetPasswd string
}
var dataConfig configFile
func createConfigFile() {
reader := bufio.NewReader(os.Stdin)
fmt.Println("让我们填写应用程序的配置文件。")
fmt.Println("你的网关IP是什么？")
readGateway, err := reader.ReadString('\n')
if err != nil {
log.Fatal(err)
}
dataConfig.gateway = net.ParseIP(readGateway)
if dataConfig.gateway == nil {
log.Fatal("出现问题")
} else {
fmt.Println("你的网关是：", dataConfig.gateway.String())
}
}
我的问题是：
我想从命令行读取一个IP地址，并将其存储在configFile对象中，稍后我将使用该对象创建一个包含程序所有配置的.json文件。
当我从命令行读取IP地址时，readGateway变量正确地存储了它，这是预期的，但是当我尝试执行dataConfig.gateway = net.ParseIP(readGateway)并将字符串对象转换为net.IP对象时，我始终在dataConfig.gateway字段中得到一个nil，因此我无法使用该参数，也无法将其转换为字符串。
有人可以帮助我吗？
提前感谢。
英文:
I'm coding in golang some tools to make my life easier and I'm not understanding at all how the types in the net package works. This is part of my code:
import (
"bufio"
"fmt"
"log"
"net"
"os"
)
type configFile struct {
gateway, net net.IP
mask, port int
telnetUser, telnetPasswd string
}
var dataConfig configFile
func createConfigFile() {
reader := bufio.NewReader(os.Stdin)
fmt.Println("Let's fill te config file for the application.")
fmt.Println("Which is your gateway IP?")
readGateway, err := reader.ReadString('\n')
if err != nil {
log.Fatal(err)
}
dataConfig.gateway = net.ParseIP(readGateway)
if dataConfig.gateway == nil {
log.Fatal("Problem here")
} else {
fmt.Println("Your gateway is: ", dataConfig.gateway.String())
}
}
My problem is the next:
I want to read an IP address from the command line and storage it in the configFile object, which I will user later to create a .json file with all the configuration of my program.
When I read from the command line the IP address the readGateway variable storages it ok, that's expected, but when I try to make
dataConfig.gateway = net.ParseIP(readGateway)
and I try to cast the string object to a net.IP object I'm always getting a nill in the dataConfig.gateway field, so I'm not able to work with that parameter neither convert it to a string.
Could somebody help me?
Thanks in advance.
答案1
得分: 1
net.ParseIP(s string)的文档说明中提到，如果提供的字符串s不是有效的IP地址的文本表示形式，该函数将返回nil值，所以这一定是情况。
在调用net.ParseIP之前，请记录字符串s，以便您可以检查在程序中是否正确传递和读取它。
英文:
The documentation of net.ParseIP(s string) states that if the string s provided is not a valid textual representation of an IP address the function will return a nil value, so that must be the case.
Please log the string s before calling net.ParseIP so you can check if you are passing and reading it properly in the program.
答案2
得分: 1
bufio.Reader.ReadString的文档解释如下（重点标注为我的）：
ReadString 从输入中读取直到第一个出现的分隔符（delim），返回一个包含数据的字符串，包括分隔符在内。
因此，readGateway 最终会变成 "192.168.1.1\n"。换行符在一个格式正确的 IP 地址中是不存在的，这意味着当你使用 net.ParseIP 解析它时，它会将其排除为 nil。
你可以使用 strings.TrimRight 去除换行符：
readGateway, err := reader.ReadString('\n')
if err != nil {
log.Fatal(err)
}
readGateway = strings.TrimRight(readGateway, "\n")
英文:
bufio.Reader.ReadString's docs explain (emphasis mine)
> ReadString reads until the first occurrence of delim in the input,
> returning a string containing the data up to and including the
> delimiter
So readGateway ends up looking like "192.168.1.1\n". Your newline delimiter would not exist in a properly formatted IP address, which means when you parse it with net.ParseIP it's kicking it out as nil.
You can use strings.TrimRight to trim out the newline:
readGateway, err := reader.ReadString('\n')
if err != nil {
log.Fatal(err)
}
readGateway = strings.TrimRight(readGateway, "\n")
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