How to Read a File Starting from a Specific Line Number Using bufio.Scanner in Go?

Reading a File Starting from a Specific Line Number using Scanner

In Go, you can use a bufio.Scanner to read a file line by line. However, bufio.Scanner does not provide a built-in option to start reading from a specific line number.

Here's a way to extend bufio.Scanner with a custom SplitFunc that allows you to skip lines and start reading from a desired line number:

func scannerWithStartLine(input io.ReadSeeker, start int64) (*bufio.Scanner, error) {
    if _, err := input.Seek(start, 0); err != nil {
        return nil, err
    }

    scanner := bufio.NewScanner(input)

    scanner.Split(func(data []byte, atEOF bool) (n int, err error) {
        if atEOF && len(data) == 0 {
            return 0, io.EOF
        }
        for i := 0; i <p>This function takes an io.ReadSeeker (such as a file) and a starting line number, and returns a bufio.Scanner that skips lines until the starting line number is reached.</p><p>To use this extended bufio.Scanner, you can follow these steps:</p><ol>
<li>Open the file and set the starting line number.</li>
<li>Create a bufio.Scanner using the scannerWithStartLine function.</li>
<li>Call scanner.Scan() to read lines from the file, starting from the specified line number.</li>
</ol><p>Here's an example:</p><pre class="brush:php;toolbar:false">file, err := os.Open("input.txt")
if err != nil {
    // Handle error
}

startLine := 5

scanner, err := scannerWithStartLine(file, startLine)
if err != nil {
    // Handle error
}

for scanner.Scan() {
    fmt.Println(scanner.Text())
}

This code will read the lines of the file "input.txt" starting from line 5.

The above is the detailed content of How to Read a File Starting from a Specific Line Number Using bufio.Scanner in Go?. For more information, please follow other related articles on the PHP Chinese website!