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io.go
45 lines (40 loc) · 751 Bytes
/
io.go
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package util
import (
"bufio"
"errors"
"fmt"
"io"
"os"
)
func ReadFileLine(filename string, n int) (string, error) {
if n < 1 {
return "", fmt.Errorf("invalid request: line %d", n)
}
f, err := os.Open(filename)
if err != nil {
return "", err
}
defer f.Close()
bf := bufio.NewReader(f)
var line string
for numLine := 0; numLine < n; numLine ++ {
line, err = bf.ReadString('\n')
if err == io.EOF {
switch numLine {
case 0:
return "", errors.New("no lines in file")
case 1:
return "", errors.New("only 1 line")
default:
return "", fmt.Errorf("only %d lines", numLine)
}
}
if err != nil {
return "", err
}
}
if line == "" {
return "", fmt.Errorf("line %d empty", n)
}
return line, nil
}