magic man page on Ultrix

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magic(5)							      magic(5)

Name
       magic - magic file for the file command

Syntax
       /usr/lib/file/magic

Description
       The  magic file is used by the 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 file is formatted as follows:

       Byte offset
	    The byte offset is where information is found in the file. This is
	    the number of bytes from the beginning of the file	to  the	 first
	    byte of the magic number or string. This may, optionally,  be pre‐
	    ceded by a right angle bracket (>) to indicate a continuation line
	    to supply extra information in the printed message.

       Value type
	    The	 value	type is the type of the information to be found at the
	    specified byte offset.  The file data is interpreted as  the  fol‐
	    lowing valid types:

		 byte	  Unsigned char type
		 short	  Unsigned short type
		 long	  Long type
		 string	  Character (byte) string

       Optional operator
	    Describes how the value specified here should be compared with the
	    data at the desired offset.	 Valid	operator  characters  are:  an
	    equal sign, a right angle bracket, and a left angle bracket (=, >,
	    <).	 If none is specified, = is assumed.

       Value
	    The value to match. Numeric values may be decimal, octal, or hexa‐
	    decimal.   String  values are defined as regular expressions here.
	    The regular expressions used here are extended in  two  ways  from
	    regular expression definition in ed(1).

		 1.  Normally  unprintable  characters	may  be escaped with a
		     backslash (\).  The special characters \n, \b, \r, and \f
		     are allowed.  An octal representation can also be used to
		     insert any desired byte value, except 0.  Normally, regu‐
		     lar  expression  cannot  handle  such  character  values.
		     Because the backslash is  used  as	 an  escape  character
		     while  the	 regular  expression  is being read in, normal
		     occurrences of a backslash in a regular  expression  must
		     be	 escaped  with	a  second backslash. As an example, \(
		     must be written as \\( and \. must be written as \\.

		 2.  Text found in a file can also be inserted in the  printed
		     string with the use of the \\% delimiter.	All text found
		     between these delimiters is substituted  into  the	 print
		     string.

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

       major, minor type
	    The major and minor file type numbers are not used by the command.

       String to print
	    Any desired text string.  Data from the file can be included  with
	    the use of continuation lines beginning with a right angle bracket
	    (>).  Two types of continuation lines are possible,	 depending  on
	    the sign of the byte offset entry.

	    If	the byte offset is positive, the specified data can be printed
	    in the string when requested with an appropriate format.

	    If the offset is a negative number, an internal  routine  will  be
	    called  to test if a particular string is necessary and, if so, to
	    return it.

	    The byte offset number is an index to an internal  table  of  rou‐
	    tines  available for use. Two such routines are currently defined,
	    both for a.out images:

	    Byte Offset	   Returned String(s)

	    -1:		   ["old version 7 style symbol table"]
	    -2:		   ["setuid "]["setgid "]["sticky "]

Examples
       The following is an example of a script.	 The second line adds  setuid,
       setgid text, if appropriate:
       0   string ^#![ ]*\%[^ 0*\%  7,4	  %s
       >-2 long	  0			7,4   %sscript
       The following is an example of an executable image:
       >-1 long	  0		  12,3	 %s
       0   short  0413		  12,4	 demand paged pure
       >2  short  02		  12,4	 POSIX
       >2  short  01		  12,4	 SVID
       >-2 long	  0		  12,4	 %sexecutable
       >16 long	  >0		  12,4	 not stripped
       The following is an example of a text file:
       0   string ^ 1h[0-9][0-9][0-9][0-9][0-9]	 7,1  sccsfile

Files
See Also
       file(1)

								      magic(5)
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