mimemagic

Powerful and versatile MIME sniffing package using pre-compiled glob patterns, magic number signatures, xml document namespaces, and tree magic for mounted volumes, generated from the XDG shared-mime-info database.

License

The generated code in magicsigs.go, globs.go, treemagicsigs.go, namespaces.go and mediatypes.go makes this a derivative work of shared-mime-info, and therefore falls under the GPL-2.0-or-later license. See the discussion.

For an MIT licensed branch with the generated code removed, please see this. Providing a hypothetical permissively licensed freedesktop.org.xml file for parsing is still required, to redistribute the compiled executable with that license, however.

Features

All in native go, no outside dependencies/C library bindings
1003 MIME types, with a description, an acronym (where available), common aliases, extensions, icons, and subclasses
493 magic signature tests (comprising of 1147 individual patterns), featuring range searches and bit masks, as per the xdg specification
1099 glob patterns, for filename-based matching
11 Tree Magic signatures and 28 XML namespace/local name pairs, offered for completeness' sake.
Included is the xml file parser to generate your own MIME definitions
Also included is a CLI based on this library that is fully featured and blazing-fast, beating the native 'file' and KDE's 'kmimetypefinder' in performance
Cross-platform support

Installation

The library:

go get github.com/zRedShift/mimemagic/v2

The CLI:

go get github.com/zRedShift/mimemagic/v2/cmd/mimemagic

API

See the Godoc reference, and cmd/mimemagic for an example implementation.

Usage

The library:

package main

import (
    "fmt"
    "github.com/zRedShift/mimemagic/v2"
    "strings"
)

func main() {
    // Ignoring Read errors that might arise
    mimeType, _ := mimemagic.MatchFilePath("sample.svgz", -1)

    // image/svg+xml-compressed
    fmt.Println(mimeType.MediaType())

    // compressed SVG image
    fmt.Println(mimeType.Comment)

    // SVG (Scalable Vector Graphics)
    fmt.Printf("%s (%s)\n", mimeType.Acronym, mimeType.ExpandedAcronym)

    // application/gzip
    fmt.Println(strings.Join(mimeType.SubClassOf, ", "))

    // .svgz
    fmt.Println(strings.Join(mimeType.Extensions, ", "))

    // This is an image.
    switch mimeType.Media {
    case "image":
        fmt.Println("This is an image.")
    case "video":
        fmt.Println("This is a video file.")
    case "audio":
        fmt.Println("This is an audio file.")
    case "application":
        fmt.Println("This is an application.")
    default:
        fmt.Printf("This is a(n) %s.", mimeType.Media)
    }

    // true
    fmt.Println(mimeType.IsExtension(".svgz"))
}

The CLI:

Usage: mimemagic [options] <file> ...
Determines the MIME type of the given file(s).

Options:
  -c    Determine the MIME type of the file(s) using only its content.
  -f    Determine the MIME type of the file(s) using only the file name. Does
        not check for the file's existence. The -c
         flag takes precedence.
  -i    Output the MIME type in a human readable format.
  -l int
        The number of bytes from the beginning of the file mimemagic will
        examine. Reads the entire file if set to a negative value. By default
        mimemagic will only read the first 512 from stdin, however setting this
        flag to a non-default negative value will override this. (default -1)
  -t    Determine the MIME type of the directory/mounted volume using tree
        magic. Can't be used in conjunction with with -c, -f or -x.
  -x    Determine the MIME type of the xml file(s) using the local names and
        namespaces within. Can't be used in conjunction with -c, -f or -t.

Arguments:
  file
        The file(s) to test. '-' to read from stdin. If '-' is set, all other
        inputs will be ignored.

Examples:
  $ mimemagic -c sample.svgz
        application/gzip
  $ mimemagic *.svg*
        Olympic_rings_with_transparent_rims.svg: image/svg+xml
        Piano.svg.png: image/png
        RAID_5.svg: image/svg+xml
        sample.svgz: image/svg+xml-compressed
  $ cat /dev/urandom | mimemagic -
        application/octet-stream
  $ ls software; mimemagic -i -t software/
        autorun
        UNIX software

Benchmarks

See Benchmarks. For Match(), the average across over 400 completely different files (representing a unique MIME type each) is 13 ± 7 μs/op. For MatchGlob() it's 900 ± 200 ns/op, and for 12 ± 7 μs/op MatchMagic().

zRedShift / mimemagic

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