Golang, is there a better way read a file of integers into an array?

I need to read a file of integers into an array. I have it working with this:

package main

import (
    "fmt"
    "io"
    "os"
)

func readFile(filePath string) (numbers []int) {
    fd, err := os.Open(filePath)
    if err != nil {
        panic(fmt.Sprintf("open %s: %v", filePath, err))
    }
    var line int
    for {

        _, err := fmt.Fscanf(fd, "%d\n", &line)

        if err != nil {
            fmt.Println(err)
            if err == io.EOF {
                return
            }
            panic(fmt.Sprintf("Scan Failed %s: %v", filePath, err))

        }
        numbers = append(numbers, line)
    }
    return
}

func main() {
    numbers := readFile("numbers.txt")
    fmt.Println(len(numbers))
}

The file numbers.txt is just:

1
2
3
...

ReadFile() seems too long (maybe because of the error handing).

Is there a shorter / more Go idiomatic way to load a file?

1 Like

Using a bufio.Scanner makes things nice. I’ve also used an io.Reader rather than taking a filename. Often that’s a good technique, since it allows the code to be used on any file-like object and not just a file on disk. Here it’s “reading” from a string.

package main

import (
    "bufio"
    "fmt"
    "io"
    "strconv"
    "strings"
)

// ReadInts reads whitespace-separated ints from r. If there's an error, it
// returns the ints successfully read so far as well as the error value.
func ReadInts(r io.Reader) ([]int, error) {
    scanner := bufio.NewScanner(r)
    scanner.Split(bufio.ScanWords)
    var result []int
    for scanner.Scan() {
        x, err := strconv.Atoi(scanner.Text())
        if err != nil {
            return result, err
        }
        result = append(result, x)
    }
    return result, scanner.Err()
}

func main() {
    tf := "1\n2\n3\n4\n5\n6"
    ints, err := ReadInts(strings.NewReader(tf))
    fmt.Println(ints, err)
}

Refer: golang-is-there-a-better-way-read-a-file-of-integers-into-an-array