从Golang文件中读取特定字符

Question

I want to read a text file character by character and print invalid input for those characters that exceed "H"and numbers that exceed "8". eg: my input is

I9,A2
A10,C3
D2,L3

output: invalid input for all three

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"
)

func readLines(path string) ([]string, error) {
    file, err := os.Open(path)
    if err != nil {
        return nil, err
    }
    defer file.Close()
    var lines []string
    scanner := bufio.NewScanner(file)
    for scanner.Scan() {
        lines = append(lines, scanner.Text())
    }
    return lines, scanner.Err()
}

func main() {
    lines, err := readLines("chessin.txt")
    if err != nil {
        log.Fatalf("readLines: %s", err)
    }
    var numLines int = len(lines)
    for i := 0; i < numLines; i++ {
        for j := 0; j < len(lines[i]); j++ {
            if j > 'H' {
                fmt.Printf("invalid input")
            }
        }
    }
}

Answer 1

You need to edit the inner loop to check for every input line,
and find the number then comma and so, like this working sample code:

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"
    "strconv"
    "strings"
)

func readLines(path string) ([]string, error) {
    file, err := os.Open(path)
    if err != nil {
        return nil, err
    }
    defer file.Close()
    var lines []string
    scanner := bufio.NewScanner(file)
    for scanner.Scan() {
        lines = append(lines, scanner.Text())
    }
    return lines, scanner.Err()
}
func checkOne(letter byte, number, i, j int) {
    if letter > 'H' {
        fmt.Printf("invalid input %q @ (%d, %d) 
", letter, i, j)
    }
    if number > 8 {
        fmt.Printf("invalid input number %d @ (%d, %d) 
", number, i, j+1)

    }
}
func main() {
    lines, err := readLines("chessin.txt")
    if err != nil {
        log.Fatalf("readLines: %s", err)
    }
    var numLines int = len(lines)
    for i := 0; i < numLines; i++ {
        line := lines[i]
        j := 0
        comma := strings.IndexByte(line, ',')
        if comma == -1 {
            log.Fatalf("comma not found at line: %d", i)
        }
        number, err := strconv.Atoi(line[j+1 : comma])
        if err != nil {
            log.Fatalf("line:%d err: %s", i, err)
        }
        checkOne(line[j], number, i, j)

        j = comma + 1
        number, err = strconv.Atoi(line[j+1:])
        if err != nil {
            log.Fatalf("line:%d err: %s", i, err)
        }
        checkOne(line[j], number, i, j)
    }
}

input file "chessin.txt":

I9,A2
A10,C3
D2,L3

output:

invalid input 'I' @ (0, 0) 
invalid input number 9 @ (0, 1) 
invalid input number 10 @ (1, 1) 
invalid input 'L' @ (2, 3)