magic(4)							   File Formats 							  magic(4)

NAME

       magic - file command's magic number file

SYNOPSIS

       /etc/magic

DESCRIPTION

       The file(1) command identifies the type of a file using, among other tests, a test for whether the file begins with a certain magic number.
       The /etc/magic file, or a file specified as an option-argument to the -m or -M options of file(1), specifies what magic numbers are  to	be
       tested for, what message to print if a particular magic number is found, and additional information to extract from the file.

       Each  line of the file specifies a position-sensitive test to perform. A test compares the data starting at a particular offset in the file
       with a 1-byte, 2-byte, 4-byte, or 8-byte numeric value or string. If the test succeeds, a message is printed. The line consists of the fol-
       lowing fields (separated by tabs): offset type value message

       offset	  A number specifying the offset, in bytes, into the file of the data which is to be tested.

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

		  byte, d1, dC		  A one-byte signed value.

		  short, d2, dS 	  A 2-byte signed value.

		  long, d4, dI, dL, d	  A 4-byte signed value.

		  llong, d8		  An 8-byte signed value

		  ubyte, u1, uC 	  A one-byte unsigned value.

		  ushort, u2, uS	  A 2-byte unsigned value.

		  ulong, u4, uI, uL, u	  A 4-byte unsigned value.

		  ullong, u8		  An 8-byte unsigned value.

		  string, s		  A string of bytes.

		  All  type  specifiers,  except for string and s, may be followed by a mask specifier of the form &number. If a mask specifier is
		  given, the value is AND'ed with the number before any comparisons are done. The number is specified in C form. For instance,	13
		  is decimal, 013 is octal, and 0x13 is hexadecimal.

       value	  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 (for instance, 
 for NEWLINE).

		  Numeric values may be preceded by a character indicating the operation to be performed, as follows:

		  =    The value from the file must equal the specified value.

		  <    The value from the file must be less than the specified value.

		  >    The value from the file must be greater than the specified value.

		  &    All the bits in the specified value must be set in the value from the file.

		  ^    At least one of the bits in the specified value must not be set in the value from the file.

		  x    Any value will match.

		  If the character is omitted, it is assumed to be "=".

		  For comparison of numeric values, the sign and size of both the value in the file and the value from	the  value  field  of  the
		  magic  entry	will match that of the corresponding type field. If there is a non-zero mask (&) in the type field, the comparison
		  will be unsigned.

		  For string values, the byte string from the file must match the specified byte string. The byte string from the  file  which	is
		  matched is the same length as the specified byte string. If the value is a string, it can contain the following sequences:

		  character	 The backslash-escape sequences \, a, , f, 
, 
, 	, v.

		  octal	 Octal	sequences  that can be used to represent characters with specific coded values. An octal sequence consists
				 of a backslash followed by the longest sequence of one, two, or three octal-digit characters(01234567).

       message	  The message to be printed if the comparison succeeds. If the string contains a printf(3C) format specification, the  value  from
		  the file (with any specified masking performed) is printed using the message as the format string.

       Some  file  formats  contain additional information which is to be printed along with the file type. A line which begins with the character
       ">" indicates additional tests and messages to be printed. If the test on the line preceding the first line with a ">" succeeds, the  tests
       specified  in  all  the subsequent lines beginning with ">" are performed, and the messages are printed if the tests succeed. The next line
       which does not begin with a ">" terminates this.

FILES

       /etc/magic

SEE ALSO

       file(1), file(1B), printf(3C)

NOTES

       In Solaris 9 and prior releases, the file utility may have performed unsigned comparisons for types byte, short, and long. Old user-defined
       magic  files,  which  were  specified  with  the  -m option, will need modification of byte, short, and long entries to their corresponding
       unsigned types (ubyte, ushort, or ulong) for those entries for which all of the following are true:

	   o	  The entry uses the "<" or the ">" operator.

	   o	  The type field does not contain a non-zero mask.

	   o	  The intention of the entry is to test unsigned values.

       For example, if the following entry is expected to match any non-zero, one-byte value from the file, including values for  which  the  sign
       bit is on:

	 #offset type	 value	 message
	 0	 byte	 >0	 this matches any non-zero value

       then that entry should be changed to:

	 0	 ubyte	  >0	 this matches any non-zero value

       In Solaris 7 through Solaris 9, when applying tests for magic file entries whose type field is the numeric type "short" or "long", the file
       utility in the x86 environment would switch the byte order of the numeric values read. Starting in Solaris 10, the byte order will  not	be
       switched  on  x86.  A  test  for a numeric value whose byte order is identical in both little- and big-endian architectures may require two
       magic file entries, to ensure that the test correctly identifies files in both environments. For example, a  magic  file  entry	that  will
       match on a big-endian system may look like this:

	 0	 long	   0xf00000ff	   extended accounting file

       Its corresponding magic file entry that will match the same value on a little-endian system would look like this:

	 0	 long	   0xff0000f0	   extended accounting file

BUGS

       There should be more than one level of subtests, with the level indicated by the number of `>' at the beginning of the line.

SunOS 5.11							    6 Feb 2004								  magic(4)