file

Documentation

Overview

package file provides functions that can be used to retrieve files from local and remote locations.

Index

• func Get(ctx context.Context, location string) (string, error)

Examples

• Get (Http)
• Get (Local)

Functions

func Get

func Get(ctx context.Context, location string) (string, error)

Get retrieves a file from these locations (in order):

- Local disk

- HTTP or HTTPS URL

- AWS S3

If a file is found, then it is saved as a temporary local file and the name is returned. The caller is responsible for removing files when they are no longer needed; files should be removed even if an error occurs.

Example (Http)

package main

import (
	"context"
	"fmt"
	"os"
	"strings"

	"github.com/brexhq/substation/internal/file"
)

func main() {
	location := "https://example.com"

	// a local copy of the HTTP body is created and must be removed when it's no longer needed, regardless of errors
	path, err := file.Get(context.TODO(), location)
	defer os.Remove(path)

	if err != nil {
		// handle err
		panic(err)
	}

	f, err := os.Open(path)
	if err != nil {
		// handle err
		panic(err)
	}

	defer f.Close()

	buf := make([]byte, 16)
	if _, err = f.Read(buf); err != nil {
		// handle err
		panic(err)
	}

	prefix := strings.HasPrefix(strings.ToUpper(string(buf)), "<!DOCTYPE")
	fmt.Println(prefix)

}

Output:

true

Example (Local)

package main

import (
	"context"
	"fmt"
	"io"
	"os"

	"github.com/brexhq/substation/internal/file"
)

func main() {
	// temp file is used to simulate an open file and must be removed after the test completes
	temp, _ := os.CreateTemp("", "substation")
	defer os.Remove(temp.Name())
	defer temp.Close()

	_, _ = temp.Write([]byte("foo\nbar\nbaz"))

	// a local copy of the file is created and must be removed when it's no longer needed, regardless of errors
	path, err := file.Get(context.TODO(), temp.Name())
	defer os.Remove(path)

	if err != nil {
		// handle err
		panic(err)
	}

	f, err := os.Open(path)
	if err != nil {
		// handle err
		panic(err)
	}

	defer f.Close()

	buf, err := io.ReadAll(f)
	if err != nil {
		// handle err
		panic(err)
	}

	fmt.Println(string(buf))

}

Output:

foo
bar
baz