Golang : Find out mime type from bytes in buffer
Problem :
You are building an application that need to detect the MIME type of an object. Such as an email application that handles file attachment. How to find out the MIME type of an object or file ?
Solution :
Use net/http.DetectContentType()
function to detect the file or object MIME type. For example :
package main
import (
"fmt"
"net/http"
"os"
)
func main() {
filename := os.Args[1]
if len(os.Args) != 2 {
fmt.Println("Missing filename argument")
fmt.Printf("Usage : %s filename\n", os.Args[0])
os.Exit(0)
}
fmt.Println(filename)
file, err := os.Open(filename)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
buff := make([]byte, 512)
_, err = file.Read(buff)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
filetype := http.DetectContentType(buff)
fmt.Println("File type or MIME type : ", filetype)
}
Sample output :
img.gif
File type or MIME type : image/gif
img.pdf
File type or MIME type : application/pdf
Reference :
See also : Golang : How to verify uploaded file is image or allowed file types
By Adam Ng
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