files

File Utilities

The files package provides utilities for working with files in Go applications, including both local file operations and embedded filesystem access.

Features

• DownloadURL: Download files from URLs to local filesystem
• SaveToTempDir: Save multipart files to temporary directory
• EmbeddedFileToBytes: Read files from embedded filesystem as byte slices
• EmbeddedFileToString: Read files from embedded filesystem as strings

Installation

import "github.com/dracory/base/files"

Usage

Downloading Files from URLs

err := files.DownloadURL("https://example.com/file.pdf", "local/path/file.pdf")
if err != nil {
    log.Fatal(err)
}

Saving Uploaded Files to Temp Directory

// Assuming you have a multipart.File from an HTTP upload
tempPath, err := files.SaveToTempDir("uploaded.jpg", uploadedFile)
if err != nil {
    log.Fatal(err)
}
fmt.Printf("File saved to: %s", tempPath)

Reading Embedded Files

//go:embed templates/*.html
var templateFS embed.FS

// Read as bytes
bytes, err := files.EmbeddedFileToBytes(templateFS, "templates/index.html")
if err != nil {
    log.Fatal(err)
}

// Read as string
content, err := files.EmbeddedFileToString(templateFS, "templates/index.html")
if err != nil {
    log.Fatal(err)
}
fmt.Println(content)

Functions

DownloadURL(url string, localFilepath string) error

Downloads a file from a URL to a local file path. Efficient because it writes as it downloads rather than loading the entire file into memory.

Parameters:

• url: URL to download from
• localFilepath: Local file path to save the file

Returns:

• error: Error if download fails

SaveToTempDir(fileName string, file multipart.File) (string, error)

Saves a multipart file to a temporary directory with the appropriate file extension.

Parameters:

• fileName: Original filename (used for extension)
• file: Multipart file to save

Returns:

• string: Path to the saved temporary file
• error: Error if save fails

EmbeddedFileToBytes(embeddedFileSystem embed.FS, path string) ([]byte, error)

Reads a file from the embedded filesystem and returns its content as a byte slice.

Parameters:

• embeddedFileSystem: The embedded filesystem (embed.FS)
• path: Path to the file within the embedded filesystem

Returns:

• []byte: File content as bytes
• error: Error if file cannot be read

EmbeddedFileToString(embeddedFileSystem embed.FS, path string) (string, error)

Reads a file from the embedded filesystem and returns its content as a string.

Parameters:

• embeddedFileSystem: The embedded filesystem (embed.FS)
• path: Path to the file within the embedded filesystem

Returns:

• string: File content as string
• error: Error if file cannot be read

Examples

Web Application File Upload

func uploadHandler(w http.ResponseWriter, r *http.Request) {
    file, header, err := r.FormFile("upload")
    if err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return
    }
    defer file.Close()
    
    tempPath, err := files.SaveToTempDir(header.Filename, file)
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
    
    // Process the file at tempPath...
    fmt.Fprintf(w, "File uploaded to: %s", tempPath)
}

Embedded Template System

//go:embed templates/*.html
var templateFS embed.FS

func renderTemplate(templateName string, data interface{}) (string, error) {
    content, err := files.EmbeddedFileToString(templateFS, "templates/"+templateName)
    if err != nil {
        return "", err
    }
    
    // Process template with data...
    return content, nil
}

Testing

The package includes comprehensive tests for all functionality:

go test ./files

Dependencies

• Go 1.16+ (for embed support)
• No external dependencies

Migration Notes

This package was created by merging the previous filesystem package functionality into the existing files package to eliminate redundancy. If you were previously importing github.com/dracory/base/filesystem, update your imports to github.com/dracory/base/files.

Previous:

import "github.com/dracory/base/filesystem"

Current:

import "github.com/dracory/base/files"