mmmagic

Use the Magic class to inspect files or buffers. You can configure the output format (e.g., general description vs. MIME type) by passing bitmask flags to the constructor.

Common Usage Patterns

1. Get general description of a file By default, new Magic() returns a human-readable description.

2. Get MIME type for a file Pass mmm.MAGIC_MIME_TYPE to the constructor to receive the MIME type string.

3. Get MIME type and encoding Pass mmm.MAGIC_MIME (which is a combination of MAGIC_MIME_TYPE and MAGIC_MIME_ENCODING) to receive the MIME type and charset (e.g., application/x-dosexec; charset=binary).

4. Inspect a Buffer Use the .detect(buffer, callback) method to inspect raw data without a file path.

var mmm = require('mmmagic'),
    Magic = mmm.Magic;

// Get MIME type and encoding
var magic = new Magic(mmm.MAGIC_MIME);
magic.detectFile('path/to/file', function(err, result) {
    if (err) throw err;
    console.log(result); // e.g., 'application/x-dosexec; charset=binary'
});

// Inspect a Buffer
var buf = Buffer.from('import Options\nfrom os import unlink, symlink');
magic.detect(buf, function(err, result) {
    if (err) throw err;
    console.log(result); // e.g., 'Python script, ASCII text executable'
});

The Magic constructor creates a new instance for file inspection.

Signature: new Magic(magicSource, flags)

• magicSource (optional):
  • A String path to a compatible magic file.
  • A Buffer containing the contents of a compatible magic file.
  • false: Tells mmmagic to search for a magic file using the MAGIC environment variable or standard filesystem paths.
  • If not provided or not false, the bundled magic file is used.
• flags (optional): A bitmask of constants available on the require('mmmagic') object to configure behavior.

Available Flags:

// Available constants on the mmmagic module:
// MAGIC_NONE, MAGIC_DEBUG, MAGIC_SYMLINK, MAGIC_DEVICES, 
// MAGIC_MIME_TYPE, MAGIC_CONTINUE, MAGIC_CHECK, MAGIC_PRESERVE_ATIME, 
// MAGIC_RAW, MAGIC_MIME_ENCODING, MAGIC_MIME, MAGIC_APPLE, 
// MAGIC_NO_CHECK_TAR, MAGIC_NO_CHECK_SOFT, MAGIC_NO_CHECK_APPTYPE, 
// MAGIC_NO_CHECK_ELF, MAGIC_NO_CHECK_TEXT, MAGIC_NO_CHECK_CDF, 
// MAGIC_NO_CHECK_TOKENS, MAGIC_NO_CHECK_ENCODING

The following flags can be used with the Magic constructor to modify inspection behavior. These are accessible as constants on the require('mmmagic') object.

MAGIC_NONE                - No flags set
MAGIC_DEBUG               - Turn on debugging
MAGIC_SYMLINK             - Follow symlinks (default for non-Windows)
MAGIC_DEVICES             - Look at the contents of devices
MAGIC_MIME_TYPE           - Return the MIME type
MAGIC_CONTINUE            - Return all matches (returned as an array of strings)
MAGIC_CHECK               - Print warnings to stderr
MAGIC_PRESERVE_ATIME      - Restore access time on exit
MAGIC_RAW                 - Don't translate unprintable chars
MAGIC_MIME_ENCODING       - Return the MIME encoding
MAGIC_MIME               - (MAGIC_MIME_TYPE | MAGIC_MIME_ENCODING)
MAGIC_APPLE               - Return the Apple creator and type
MAGIC_NO_CHECK_TAR        - Don't check for tar files
MAGIC_NO_CHECK_SOFT       - Don't check magic entries
MAGIC_NO_CHECK_APPTYPE    - Don't check application type
MAGIC_NO_CHECK_ELF        - Don't check for elf details
MAGIC_NO_CHECK_TEXT       - Don't check for text files
MAGIC_NO_CHECK_CDF        - Don't check for cdf files
MAGIC_NO_CHECK_TOKENS     - Don't check tokens
MAGIC_NO_CHECK_ENCODING   - Don't check text encodings

The mmmagic module exports several bitwise flags used to configure how file identification is performed. These flags can be combined using bitwise OR (|) to request multiple behaviors (e.g., returning both MIME type and encoding).

{
  MAGIC_NONE: 0x000000,           /* No flags (default for Windows) */
  MAGIC_DEBUG: 0x000001,          /* Turn on debugging */
  MAGIC_SYMLINK: 0x000002,       /* Follow symlinks (default for *nix) */
  MAGIC_DEVICES: 0x000008,       /* Look at the contents of devices */
  MAGIC_MIME_TYPE: 0x000010,     /* Return the MIME type */
  MAGIC_CONTINUE: 0x000020,      /* Return all matches */
  MAGIC_CHECK: 0x000040,         /* Print warnings to stderr */
  MAGIC_PRESERVE_ATIME: 0x000080, /* Restore access time on exit */
  MAGIC_RAW: 0x000100,           /* Don't translate unprintable chars */
  MAGIC_MIME_ENCODING: 0x000400, /* Return the MIME encoding */
  MAGIC_MIME: (0x000010|0x000400),/* (MAGIC_MIME_TYPE|MAGIC_MIME_ENCODING) */
  MAGIC_APPLE: 0x000800,         /* Return the Apple creator and type */

  /* Check suppression flags */
  MAGIC_NO_CHECK_TAR: 0x002000,    /* Don't check for tar files */
  MAGIC_NO_CHECK_SOFT: 0x004000,   /* Don't check magic entries */
  MAGIC_NO_CHECK_APPTYPE: 0x008000, /* Don't check application type */
  MAGIC_NO_CHECK_ELF: 0x010000,    /* Don't check for elf details */
  MAGIC_NO_CHECK_TEXT: 0x020000,   /* Don't check for text files */
  MAGIC_NO_CHECK_CDF: 0x040000,    /* Don't check for cdf files */
  MAGIC_NO_CHECK_TOKENS: 0x100000, /* Don't check tokens */
  MAGIC_NO_CHECK_ENCODING: 0x200000 /* Don't check text encodings */
}