英文:
program only prints last string of input file
问题
我正在尝试创建一个简单的程序，用于从文本文件中读取行并将它们打印到控制台中。我花了很多时间检查我的代码，但我无法理解为什么只有最后一行被打印到屏幕上。有人可以告诉我我在这里做错了什么吗？这里的所有内容都应该可以编译和运行。
package mainimport ("bufio""fmt""os")func Readln(r *bufio.Reader) (string, error) {var (isPrefix bool = trueerr error = nilline, ln []byte)for isPrefix && err == nil {line, isPrefix, err = r.ReadLine()ln = append(ln, line...)}return string(ln), err}func main() {f, err := os.Open("tickers.txt")if err != nil {fmt.Printf("打开文件时出错：%v\n", err)os.Exit(1)}r := bufio.NewReader(f)s, e := Readln(r)for e == nil {fmt.Println(s)s, e = Readln(r)}}
这段代码的问题在于，你只调用了一次Readln函数来读取文件的第一行，然后在一个循环中重复打印这一行。你需要在循环中继续调用Readln函数来读取文件的下一行。以下是修改后的代码：
package mainimport ("bufio""fmt""os")func Readln(r *bufio.Reader) (string, error) {var (isPrefix bool = trueerr error = nilline, ln []byte)for isPrefix && err == nil {line, isPrefix, err = r.ReadLine()ln = append(ln, line...)}return string(ln), err}func main() {f, err := os.Open("tickers.txt")if err != nil {fmt.Printf("打开文件时出错：%v\n", err)os.Exit(1)}r := bufio.NewReader(f)for {s, e := Readln(r)if e != nil {break}fmt.Println(s)}}
这样修改后，程序将会循环读取文件的每一行并将其打印到控制台上。
英文:
i am trying to create a simple program to read lines from a text file and print them out to the console in golang. I spent lots of time going over my code and I simply can't understand why only the last line is being printed out to the screen. can anyone tell me where I am going wrong here? Everything here should compile and run.
package mainimport ("bufio""fmt""os")func Readln(r *bufio.Reader) (string, error) {var (isPrefix bool = trueerr error = nilline, ln []byte)for isPrefix && err == nil {line, isPrefix, err = r.ReadLine()ln = append(ln, line...)}return string(ln), err}func main() {f, err := os.Open("tickers.txt")if err != nil {fmt.Printf("error opening file: %v\n", err)os.Exit(1)}r := bufio.NewReader(f)s, e := Readln(r)for e == nil {fmt.Println(s)s, e = Readln(r)}}
答案1
得分: 1
因此，我怀疑问题出在你的tickers.txt文件的行尾符上。ReadLine()的文档还指出，在大多数情况下，Scanner更适合使用。
以下的Stack Overflow问题提供了一些有关替代实现的有用信息：https://stackoverflow.com/questions/8757389/reading-file-line-by-line-in-go
然后，我使用上述问题中的示例来重新实现你的main函数，代码如下：
f, err := os.Open("tickers.txt")if err != nil {fmt.Printf("打开文件时出错：%v\n", err)os.Exit(1)}scanner := bufio.NewScanner(f)for scanner.Scan() {fmt.Println(scanner.Text())}if err := scanner.Err(); err != nil {fmt.Println(err)}
英文:
I therefore suspect that the problem is in your tickers.txt file line endings. The docs for ReadLine() also indicate that for most situations a Scanner is more suitable.
The following SO question has some useful information for alternative implementations: https://stackoverflow.com/questions/8757389/reading-file-line-by-line-in-go
I then used the example in the above question to re-implement your main function as follows:
f, err := os.Open("tickers.txt")if err != nil {fmt.Printf("error opening file: %v\n", err)os.Exit(1)}scanner := bufio.NewScanner(f)for scanner.Scan() {fmt.Println(scanner.Text())}if err := scanner.Err(); err != nil {fmt.Println(err)}
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