How to read the contents of a text file into a variable in Golang?

Reading a Text File in Golang

How can I read the contents of "file.txt" into a variable in Golang?

package main

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

func main() {
    file, err := os.Open("file.txt")
    if err != nil {
        log.Fatal(err)
    }

    fmt.Print(file)
}

Answer:

The provided code successfully reads the file, but it prints the pointer value of the file descriptor rather than the file content. To obtain the file content, you need to read from the file descriptor.

Options for Reading File Content:

• ReadAll: Reads all file content into memory as bytes.

b, err := io.ReadAll(file)
fmt.Print(b)

• Read in Chunks: Reads the file content in smaller chunks to avoid memory issues with large files.

buf := make([]byte, 32*1024) // Define your buffer size.

for {
    n, err := file.Read(buf)

    if n > 0 {
        fmt.Print(buf[:n]) // Your read buffer.
    }

    if err == io.EOF {
        break
    }
    if err != nil {
        log.Printf("read %d bytes: %v", n, err)
        break
    }
}

• bufio Scanner: Advances the token by newline by default.

scanner := bufio.NewScanner(file)

for scanner.Scan() {
    fmt.Println(scanner.Text()) // Token in unicode-char
    fmt.Println(scanner.Bytes()) // Token in bytes
}

Additional Resources:

• [go-lang file cheatsheet](https://go-lang-file-utils.readthedocs.io/)

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