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magic(4)
NAME
  magic - Magic file for the file command

SYNOPSIS
  /etc/magic

DESCRIPTION
  The magic file is used by the file command to identify files that have some
  sort of magic number.	 A magic number is any numeric or string constant
  that identifies the file containing the constant.

  The format for the magic file is as follows:

       offset	type   operator,value	string

  The fields should be separated by tabs.  Each record must be contained on
  one line.

  The fields contain the following data:

  Byte Offset
    This field contains the number of bytes from the beginning of the file on
    which you are running the file command to the first byte of the magic
    number of character string you want to identify.  Use a right angle
    bracket (>) to indicate a continuation line that supplies additional
    information describing the file.

  Value Type
    This field contains information about the data type of the magic number
    or character string at the specified byte offset.  Valid data types for
    this field are:

    byte
	Unsigned character type

    short
	Unsigned short type

    long
	Long type

    string
	Character (byte) string

  Comparison Operator
    This field contains instructions for the file command on how to compare
    the value read from the file being checked with the value stored in the
    Value Type field of the magic file.	 The valid comparison operators are:

    = The two values are equal.

    > The value in the file being checked is greater than the value in the
      magic file.

    < The value in the file being checked is less than the value in the magic
      file.

    & All the bits in the magic file value must be set in the value from the
      file being checked.

    Note that the Comparison Operator field is optional.  If you do not
    specify the operator, the values are expected to be equal.

  Value
    This field contains the value used to compare what is read from the file
    being checked by the file command.	You can use decimal, hex, or octal
    numbers in this field or character strings in the form of regular
    expressions.

    Precede all hex numbers with the characters zero and x (for example,
    0x80). To specify an octal number, precede it with a zero (for example,
    0200).  Decimal numbers require no special representation and should be
    written as integers (for example, 128).

    The rules for specifying character strings follow those of the ed editor
    (see ed(1)) for regular expressions, with two extensions:

    - You use the backslash (\) to escape an unprintable character.  The
      string can contain all special character such as \n, \b, \r, and \f. If
      a backslash appears in the string, it must be escaped with a second
      backslash (\\).  You can use octal representation to specify any byte
      value other than zero (0).

    - Text found in the file can be inserted into the printed string if it is
      preceded and followed by \\% delimiters.	All text found between these
      delimiters is displayed as the print string.

    This regular expression search never terminates until a match is
    explicitly found or rejected.  The special character \n is a valid
    character in the patterns.	Therefore, the pattern .* should never be
    used here.

  String
    This field contains the string to print. The string provides information
    about the file. The string can include text found in the file when
    requested with an appropriate printf() format.

EXAMPLES
  The following is an example of a script:

       string ^#!{ }*\\%[^ \n]*\\%     %s

  The following are examples of executable images:

       >2	short	02		       POSIX
       >2	short	01		       SVID
       >16	long	>0		       not stripped

  The following are examples of text and data files:

       0       string  ^\01h[0-9][0-9][0-9][0-9][0-9]	sccsfile
       0       string  ^#ifndef				c program
       0       string  ^070707				ASCII cpio archive

FILES
  /etc/magic

RELATED INFORMATION
  Commands:  file(1)

Index for Section 4

Alphabetical listing for M

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