Data commit

Task/Read-a-specific-line-from-a-file/Go/read-a-specific-line-from-a-file.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+)
+
+func main() {
+	if line, err := rsl("input.txt", 7); err == nil {
+		fmt.Println("7th line:")
+		fmt.Println(line)
+	} else {
+		fmt.Println("rsl:", err)
+	}
+}
+
+func rsl(fn string, n int) (string, error) {
+	if n < 1 {
+		return "", fmt.Errorf("invalid request: line %d", n)
+	}
+	f, err := os.Open(fn)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+	bf := bufio.NewReader(f)
+	var line string
+	for lnum := 0; lnum < n; lnum++ {
+		line, err = bf.ReadString('\n')
+		if err == io.EOF {
+			switch lnum {
+			case 0:
+				return "", errors.New("no lines in file")
+			case 1:
+				return "", errors.New("only 1 line")
+			default:
+				return "", fmt.Errorf("only %d lines", lnum)
+			}
+		}
+		if err != nil {
+			return "", err
+		}
+	}
+	if line == "" {
+		return "", fmt.Errorf("line %d empty", n)
+	}
+	return line, nil
+}