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MAGIC(5)		    BSD File Formats Manual		      MAGIC(5)

NAME
     magic -- file command's magic pattern file

DESCRIPTION
     This manual page documents the format of magic files as used by the
     file(1) command, version 5.34.  The file(1) command identifies the type
     of a file using, among other tests, a test for whether the file contains
     certain ``magic patterns''.  The database of these ``magic patterns'' is
     usually located in a binary file in /usr/share/misc/magic.mgc or a direc-
     tory of source text magic pattern fragment files in
     /usr/share/misc/magic.  The database specifies what patterns are to be
     tested for, what message or MIME type to print if a particular pattern is
     found, and additional information to extract from the file.

     The format of the source fragment files that are used to build this data-
     base is as follows: Each line of a fragment file specifies a test to be
     performed.	 A test compares the data starting at a particular offset in
     the file with a byte value, a string or a numeric value.  If the test
     succeeds, a message is printed.  The line consists of the following
     fields:

     offset   A number specifying the offset (in bytes) into the file of the
	      data which is to be tested.  This offset can be a negative num-
	      ber if it is:
	      o	  The first direct offset of the magic entry (at continuation
		  level 0), in which case it is interpreted an offset from end
		  end of the file going backwards.  This works only when a
		  file descriptor to the file is a available and it is a regu-
		  lar file.
	      o	  A continuation offset relative to the end of the last up-
		  level field (&).

     type     The type of the data to be tested.  The possible values are:

	      byte	  A one-byte value.

	      short	  A two-byte value in this machine's native byte
			  order.

	      long	  A four-byte value in this machine's native byte
			  order.

	      quad	  An eight-byte value in this machine's native byte
			  order.

	      float	  A 32-bit single precision IEEE floating point number
			  in this machine's native byte order.

	      double	  A 64-bit double precision IEEE floating point number
			  in this machine's native byte order.

	      string	  A string of bytes.  The string type specification
			  can be optionally followed by /[WwcCtbT]*.  The
			  ``W'' flag compacts whitespace in the target, which
			  must contain at least one whitespace character.  If
			  the magic has n consecutive blanks, the target needs
			  at least n consecutive blanks to match.  The ``w''
			  flag treats every blank in the magic as an optional
			  blank.  The ``c'' flag specifies case insensitive
			  matching: lower case characters in the magic match
			  both lower and upper case characters in the target,
			  whereas upper case characters in the magic only
			  match upper case characters in the target.  The
			  ``C'' flag specifies case insensitive matching:
			  upper case characters in the magic match both lower
			  and upper case characters in the target, whereas
			  lower case characters in the magic only match upper
			  case characters in the target.  To do a complete
			  case insensitive match, specify both ``c'' and
			  ``C''.  The ``t'' flag forces the test to be done
			  for text files, while the ``b'' flag forces the test
			  to be done for binary files.	The ``T'' flag causes
			  the string to be trimmed, i.e. leading and trailing
			  whitespace is deleted before the string is printed.

	      pstring	  A Pascal-style string where the first byte/short/int
			  is interpreted as the unsigned length.  The length
			  defaults to byte and can be specified as a modifier.
			  The following modifiers are supported:
			  B  A byte length (default).
			  H  A 4 byte big endian length.
			  h  A 2 byte big endian length.
			  L  A 4 byte little endian length.
			  l  A 2 byte little endian length.
			  J  The length includes itself in its count.
			  The string is not NUL terminated.  ``J'' is used
			  rather than the more valuable ``I'' because this
			  type of length is a feature of the JPEG format.

	      date	  A four-byte value interpreted as a UNIX date.

	      qdate	  A eight-byte value interpreted as a UNIX date.

	      ldate	  A four-byte value interpreted as a UNIX-style date,
			  but interpreted as local time rather than UTC.

	      qldate	  An eight-byte value interpreted as a UNIX-style
			  date, but interpreted as local time rather than UTC.

	      qwdate	  An eight-byte value interpreted as a Windows-style
			  date.

	      beid3	  A 32-bit ID3 length in big-endian byte order.

	      beshort	  A two-byte value in big-endian byte order.

	      belong	  A four-byte value in big-endian byte order.

	      bequad	  An eight-byte value in big-endian byte order.

	      befloat	  A 32-bit single precision IEEE floating point number
			  in big-endian byte order.

	      bedouble	  A 64-bit double precision IEEE floating point number
			  in big-endian byte order.

	      bedate	  A four-byte value in big-endian byte order, inter-
			  preted as a Unix date.

	      beqdate	  An eight-byte value in big-endian byte order, inter-
			  preted as a Unix date.

	      beldate	  A four-byte value in big-endian byte order, inter-
			  preted as a UNIX-style date, but interpreted as
			  local time rather than UTC.

	      beqldate	  An eight-byte value in big-endian byte order, inter-
			  preted as a UNIX-style date, but interpreted as
			  local time rather than UTC.

	      beqwdate	  An eight-byte value in big-endian byte order, inter-
			  preted as a Windows-style date.

	      bestring16  A two-byte unicode (UCS16) string in big-endian byte
			  order.

	      leid3	  A 32-bit ID3 length in little-endian byte order.

	      leshort	  A two-byte value in little-endian byte order.

	      lelong	  A four-byte value in little-endian byte order.

	      lequad	  An eight-byte value in little-endian byte order.

	      lefloat	  A 32-bit single precision IEEE floating point number
			  in little-endian byte order.

	      ledouble	  A 64-bit double precision IEEE floating point number
			  in little-endian byte order.

	      ledate	  A four-byte value in little-endian byte order,
			  interpreted as a UNIX date.

	      leqdate	  An eight-byte value in little-endian byte order,
			  interpreted as a UNIX date.

	      leldate	  A four-byte value in little-endian byte order,
			  interpreted as a UNIX-style date, but interpreted as
			  local time rather than UTC.

	      leqldate	  An eight-byte value in little-endian byte order,
			  interpreted as a UNIX-style date, but interpreted as
			  local time rather than UTC.

	      leqwdate	  An eight-byte value in little-endian byte order,
			  interpreted as a Windows-style date.

	      lestring16  A two-byte unicode (UCS16) string in little-endian
			  byte order.

	      melong	  A four-byte value in middle-endian (PDP-11) byte
			  order.

	      medate	  A four-byte value in middle-endian (PDP-11) byte
			  order, interpreted as a UNIX date.

	      meldate	  A four-byte value in middle-endian (PDP-11) byte
			  order, interpreted as a UNIX-style date, but inter-
			  preted as local time rather than UTC.

	      indirect	  Starting at the given offset, consult the magic
			  database again.  The offset of the indirect magic is
			  by default absolute in the file, but one can specify
			  /r to indicate that the offset is relative from the
			  beginning of the entry.

	      name	  Define a ``named'' magic instance that can be called
			  from another use magic entry, like a subroutine
			  call.	 Named instance direct magic offsets are rela-
			  tive to the offset of the previous matched entry,
			  but indirect offsets are relative to the beginning
			  of the file as usual.	 Named magic entries always
			  match.

	      use	  Recursively call the named magic starting from the
			  current offset.  If the name of the referenced
			  begins with a ^ then the endianness of the magic is
			  switched; if the magic mentioned leshort for exam-
			  ple, it is treated as beshort and vice versa.	 This
			  is useful to avoid duplicating the rules for differ-
			  ent endianness.

	      regex	  A regular expression match in extended POSIX regular
			  expression syntax (like egrep).  Regular expressions
			  can take exponential time to process, and their per-
			  formance is hard to predict, so their use is dis-
			  couraged.  When used in production environments,
			  their performance should be carefully checked.  The
			  size of the string to search should also be limited
			  by specifying /<length>, to avoid performance issues
			  scanning long files.	The type specification can
			  also be optionally followed by /[c][s][l].  The
			  ``c'' flag makes the match case insensitive, while
			  the ``s'' flag update the offset to the start offset
			  of the match, rather than the end.  The ``l'' modi-
			  fier, changes the limit of length to mean number of
			  lines instead of a byte count.  Lines are delimited
			  by the platforms native line delimiter.  When a line
			  count is specified, an implicit byte count also com-
			  puted assuming each line is 80 characters long.  If
			  neither a byte or line count is specified, the
			  search is limited automatically to 8KiB.  ^ and $
			  match the beginning and end of individual lines,
			  respectively, not beginning and end of file.

	      search	  A literal string search starting at the given off-
			  set.	The same modifier flags can be used as for
			  string patterns.  The search expression must contain
			  the range in the form /number, that is the number of
			  positions at which the match will be attempted,
			  starting from the start offset.  This is suitable
			  for searching larger binary expressions with vari-
			  able offsets, using \ escapes for special charac-
			  ters.	 The order of modifier and number is not rele-
			  vant.

	      default	  This is intended to be used with the test x (which
			  is always true) and it has no type.  It matches when
			  no other test at that continuation level has matched
			  before.  Clearing that matched tests for a continua-
			  tion level, can be done using the clear test.

	      clear	  This test is always true and clears the match flag
			  for that continuation level.	It is intended to be
			  used with the default test.

	      For compatibility with the Single UNIX Standard, the type speci-
	      fiers dC and d1 are equivalent to byte, the type specifiers uC
	      and u1 are equivalent to ubyte, the type specifiers dS and d2
	      are equivalent to short, the type specifiers uS and u2 are
	      equivalent to ushort, the type specifiers dI, dL, and d4 are
	      equivalent to long, the type specifiers uI, uL, and u4 are
	      equivalent to ulong, the type specifier d8 is equivalent to
	      quad, the type specifier u8 is equivalent to uquad, and the type
	      specifier s is equivalent to string.  In addition, the type
	      specifier dQ is equivalent to quad and the type specifier uQ is
	      equivalent to uquad.

	      Each top-level magic pattern (see below for an explanation of
	      levels) is classified as text or binary according to the types
	      used.  Types ``regex'' and ``search'' are classified as text
	      tests, unless non-printable characters are used in the pattern.
	      All other tests are classified as binary.	 A top-level pattern
	      is considered to be a test text when all its patterns are text
	      patterns; otherwise, it is considered to be a binary pattern.
	      When matching a file, binary patterns are tried first; if no
	      match is found, and the file looks like text, then its encoding
	      is determined and the text patterns are tried.

	      The numeric types may optionally be followed by & and a numeric
	      value, to specify that the value is to be AND'ed with the
	      numeric value before any comparisons are done.  Prepending a u
	      to the type indicates that ordered comparisons should be
	      unsigned.

     test     The value to be compared with the value from the file.  If the
	      type is numeric, this value is specified in C form; if it is a
	      string, it is specified as a C string with the usual escapes
	      permitted (e.g. \n for new-line).

	      Numeric values may be preceded by a character indicating the
	      operation to be performed.  It may be =, to specify that the
	      value from the file must equal the specified value, <, to spec-
	      ify that the value from the file must be less than the specified
	      value, >, to specify that the value from the file must be
	      greater than the specified value, &, to specify that the value
	      from the file must have set all of the bits that are set in the
	      specified value, ^, to specify that the value from the file must
	      have clear any of the bits that are set in the specified value,
	      or ~, the value specified after is negated before tested.	 x, to
	      specify that any value will match.  If the character is omitted,
	      it is assumed to be =.  Operators &, ^, and ~ don't work with
	      floats and doubles.  The operator ! specifies that the line
	      matches if the test does not succeed.

	      Numeric values are specified in C form; e.g.  13 is decimal, 013
	      is octal, and 0x13 is hexadecimal.

	      Numeric operations are not performed on date types, instead the
	      numeric value is interpreted as an offset.

	      For string values, the string from the file must match the spec-
	      ified string.  The operators =, < and > (but not &) can be
	      applied to strings.  The length used for matching is that of the
	      string argument in the magic file.  This means that a line can
	      match any non-empty string (usually used to then print the
	      string), with >\0 (because all non-empty strings are greater
	      than the empty string).

	      Dates are treated as numerical values in the respective internal
	      representation.

	      The special test x always evaluates to true.

     message  The message to be printed if the comparison succeeds.  If the
	      string contains a printf(3) format specification, the value from
	      the file (with any specified masking performed) is printed using
	      the message as the format string.	 If the string begins with
	      ``\b'', the message printed is the remainder of the string with
	      no whitespace added before it: multiple matches are normally
	      separated by a single space.

     An APPLE 4+4 character APPLE creator and type can be specified as:

	   !:apple CREATYPE

     A MIME type is given on a separate line, which must be the next non-blank
     or comment line after the magic line that identifies the file type, and
     has the following format:

	   !:mime  MIMETYPE

     i.e. the literal string ``!:mime'' followed by the MIME type.

     An optional strength can be supplied on a separate line which refers to
     the current magic description using the following format:

	   !:strength OP VALUE

     The operand OP can be: +, -, *, or / and VALUE is a constant between 0
     and 255.  This constant is applied using the specified operand to the
     currently computed default magic strength.

     Some file formats contain additional information which is to be printed
     along with the file type or need additional tests to determine the true
     file type.	 These additional tests are introduced by one or more > char-
     acters preceding the offset.  The number of > on the line indicates the
     level of the test; a line with no > at the beginning is considered to be
     at level 0.  Tests are arranged in a tree-like hierarchy: if the test on
     a line at level n succeeds, all following tests at level n+1 are per-
     formed, and the messages printed if the tests succeed, until a line with
     level n (or less) appears.	 For more complex files, one can use empty
     messages to get just the "if/then" effect, in the following way:

	   0	  string   MZ
	   >0x18  leshort  <0x40   MS-DOS executable
	   >0x18  leshort  >0x3f   extended PC executable (e.g., MS Windows)

     Offsets do not need to be constant, but can also be read from the file
     being examined.  If the first character following the last > is a ( then
     the string after the parenthesis is interpreted as an indirect offset.
     That means that the number after the parenthesis is used as an offset in
     the file.	The value at that offset is read, and is used again as an off-
     set in the file.  Indirect offsets are of the form: (( x
     [[.,][bBcCeEfFgGhHiIlmsSqQ]][+-][ y ]).  The value of x is used as an
     offset in the file.  A byte, id3 length, short or long is read at that
     offset depending on the [bBcCeEfFgGhHiIlmsSqQ] type specifier.  The value
     is treated as signed if ``'', is specified or unsigned if ``''.  is spec-
     ified.  The capitalized types interpret the number as a big endian value,
     whereas the small letter versions interpret the number as a little endian
     value; the m type interprets the number as a middle endian (PDP-11)
     value.  To that number the value of y is added and the result is used as
     an offset in the file.  The default type if one is not specified is long.
     The following types are recognized:

	   Type	   Sy Mnemonic	 Sy Endian Sy Size
	   bcBc	   Byte/Char	 N/A	   1
	   efg	   Double	 Little	   8
	   EFG	   Double	 Big	   8
	   hs	   Half/Short	 Little	   2
	   HS	   Half/Short	 Big	   2
	   i	   ID3		 Little	   4
	   I	   ID3		 Big	   4
	   m	   Middle	 Middle	   4
	   q	   Quad		 Little	   8
	   Q	   Quad		 Big	   8

     That way variable length structures can be examined:

	   # MS Windows executables are also valid MS-DOS executables
	   0	       string  MZ
	   >0x18       leshort <0x40   MZ executable (MS-DOS)
	   # skip the whole block below if it is not an extended executable
	   >0x18       leshort >0x3f
	   >>(0x3c.l)  string  PE\0\0  PE executable (MS-Windows)
	   >>(0x3c.l)  string  LX\0\0  LX executable (OS/2)

     This strategy of examining has a drawback: you must make sure that you
     eventually print something, or users may get empty output (such as when
     there is neither PE\0\0 nor LE\0\0 in the above example).

     If this indirect offset cannot be used directly, simple calculations are
     possible: appending [+-*/%&|^]number inside parentheses allows one to
     modify the value read from the file before it is used as an offset:

	   # MS Windows executables are also valid MS-DOS executables
	   0	       string  MZ
	   # sometimes, the value at 0x18 is less that 0x40 but there's still an
	   # extended executable, simply appended to the file
	   >0x18       leshort <0x40
	   >>(4.s*512) leshort 0x014c  COFF executable (MS-DOS, DJGPP)
	   >>(4.s*512) leshort !0x014c MZ executable (MS-DOS)

     Sometimes you do not know the exact offset as this depends on the length
     or position (when indirection was used before) of preceding fields.  You
     can specify an offset relative to the end of the last up-level field
     using `&' as a prefix to the offset:

	   0	       string  MZ
	   >0x18       leshort >0x3f
	   >>(0x3c.l)  string  PE\0\0	 PE executable (MS-Windows)
	   # immediately following the PE signature is the CPU type
	   >>>&0       leshort 0x14c	 for Intel 80386
	   >>>&0       leshort 0x184	 for DEC Alpha

     Indirect and relative offsets can be combined:

	   0		 string	 MZ
	   >0x18	 leshort <0x40
	   >>(4.s*512)	 leshort !0x014c MZ executable (MS-DOS)
	   # if it's not COFF, go back 512 bytes and add the offset taken
	   # from byte 2/3, which is yet another way of finding the start
	   # of the extended executable
	   >>>&(2.s-514) string	 LE	 LE executable (MS Windows VxD driver)

     Or the other way around:

	   0		     string  MZ
	   >0x18	     leshort >0x3f
	   >>(0x3c.l)	     string  LE\0\0  LE executable (MS-Windows)
	   # at offset 0x80 (-4, since relative offsets start at the end
	   # of the up-level match) inside the LE header, we find the absolute
	   # offset to the code area, where we look for a specific signature
	   >>>(&0x7c.l+0x26) string  UPX     \b, UPX compressed

     Or even both!

	   0		    string  MZ
	   >0x18	    leshort >0x3f
	   >>(0x3c.l)	    string  LE\0\0 LE executable (MS-Windows)
	   # at offset 0x58 inside the LE header, we find the relative offset
	   # to a data area where we look for a specific signature
	   >>>&(&0x54.l-3)  string  UNACE  \b, ACE self-extracting archive

     If you have to deal with offset/length pairs in your file, even the sec-
     ond value in a parenthesized expression can be taken from the file
     itself, using another set of parentheses.	Note that this additional
     indirect offset is always relative to the start of the main indirect off-
     set.

	   0		     string	  MZ
	   >0x18	     leshort	  >0x3f
	   >>(0x3c.l)	     string	  PE\0\0 PE executable (MS-Windows)
	   # search for the PE section called ".idata"...
	   >>>&0xf4	     search/0x140 .idata
	   # ...and go to the end of it, calculated from start+length;
	   # these are located 14 and 10 bytes after the section name
	   >>>>(&0xe.l+(-4)) string	  PK\3\4 \b, ZIP self-extracting archive

     If you have a list of known values at a particular continuation level,
     and you want to provide a switch-like default case:

	   # clear that continuation level match
	   >18	   clear
	   >18	   lelong  1	   one
	   >18	   lelong  2	   two
	   >18	   default x
	   # print default match
	   >>18	   lelong  x	   unmatched 0x%x

SEE ALSO
     file(1) - the command that reads this file.

BUGS
     The formats long, belong, lelong, melong, short, beshort, and leshort do
     not depend on the length of the C data types short and long on the plat-
     form, even though the Single UNIX Specification implies that they do.
     However, as OS X Mountain Lion has passed the Single UNIX Specification
     validation suite, and supplies a version of file(1) in which they do not
     depend on the sizes of the C data types and that is built for a 64-bit
     environment in which long is 8 bytes rather than 4 bytes, presumably the
     validation suite does not test whether, for example long refers to an
     item with the same size as the C data type long.  There should probably
     be type names int8, uint8, int16, uint16, int32, uint32, int64, and
     uint64, and specified-byte-order variants of them, to make it clearer
     that those types have specified widths.

BSD				 June 22, 2018				   BSD