英文:
Rookie Question: Require user to enter a valid directory in the terminal for input into Go program
问题
新手问题：我正在尝试编写一个程序，该程序接受从终端输入的目录，并在程序中对该目录执行后续操作。如果用户没有输入存在的目录，我该如何让程序继续要求用户输入有效的目录？我在这个程序上遇到的错误在底部列出。我最初尝试使用fmt.Scan()来获取用户输入，现在转向bufio扫描器，但是我不知道该怎么做，所以想请教专家。非常感谢任何帮助！
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
fmt.Println("What file path would you like to search?")
input := bufio.NewScanner(os.Stdin)
for input.Scan() {
text := input.Text()
x, _ := os.Stat(text)
if x.IsDir() {
fmt.Println("Cool this is a directory")
} else {
fmt.Println("Sorry, this is not a directory")
continue
}
}
}
错误：
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x48b465]
英文:
Rookie Question: I'm trying to write a program that takes a directory that is entered into the terminal to perform a later action in the program on that directory. If the user does not enter a directory that exists, how do I get the program to keep asking the user to enter in a valid directory? The error I'm getting on this program is listed at the bottom. I originally tried the fmt.Scan() to get the user input, have now moved onto the bufio scanner, and am at a loss so figured I would ask the experts. Much thanks for any help!
package main
import (
"bufio"
"fmt"
"os"
)
fmt.Println("What file path would you like to search?")
input := bufio.NewScanner(os.Stdin)
for input.Scan() {
text := input.Text()
x, _ := os.Stat(text)
if x.IsDir() {
fmt.Println("Cool this is a directory")
} else {
fmt.Println("Sorry, this is not a directory")
continue
}
}
}```
Error:
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x48b465]
</details>
# 答案1
**得分**: 2
你可以在os.Stat()函数中捕获错误。代码片段应该类似于这样：
```go
x, err := os.Stat(text)
if err != nil {
fmt.Println("重新输入有效的目录：")
continue
}
英文:
You could capture the error on the os.Stat() function. The code snippet would look something like this
x, err := os.Stat(text)
if err != nil {
fmt.Println("Re-enter a valid dir:")
continue
}
答案2
得分: 1
你可能想要检查Scan方法的输出以及可能发生的任何错误。
根据文档：
Scan方法将Scanner推进到下一个标记，然后可以通过Bytes或Text方法访问该标记。当扫描停止时（无论是到达输入的末尾还是发生错误），它将返回false。在Scan返回false之后，Err方法将返回扫描过程中发生的任何错误，但如果是io.EOF，则Err将返回nil。如果分割函数返回太多的空标记而不推进输入，则Scan会引发panic。这是扫描器的常见错误模式。
因此，尝试检查Err()方法是否有错误，并检查input.Scan调用的返回值。
英文:
You might want to check the output of the Scan method, and any errors that might have happened there.
According to the documentation:
> Scan advances the Scanner to the next token, which will then be
> available through the Bytes or Text method. It returns false when the
> scan stops, either by reaching the end of the input or an error.
> After Scan returns false, the Err method will return any error that
> occurred during scanning, except that if it was io.EOF, Err will
> return nil. Scan panics if the split function returns too many empty
> tokens without advancing the input. This is a common error mode for
> scanners.
So, try checking out the Err() method for any errors and checking the input.Scan call's return value.
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