MAGIC(5)                COMMAND REFERENCE                MAGIC(5)



NAME
     magic - magic number file

DESCRIPTION
     The magic file /usr/lib/magic contains information about
     certain kinds of special files that exist in the system,
     like object code files, compacted files, and archive files.
     The utility file(1) uses the magic file to print information
     about files. The subroutine notmagic(3c) uses the magic file
     to determine if a file is a special type of file, not
     suitable for printing on a terminal.

     The magic file contains three types of lines.  Lines
     beginning with the character '#' are comments and are
     ignored.  Lines beginning with '0' are considered to be
     magic number specification lines. If a line begins with a
     '>', it is a continuation of the previous line and contains
     information about following bytes.

     The format of a specification line is:

          0    type    number    description

     All fields are separated by tabs.  The type may be one of
     byte, short, long, or string.  Short numbers are interpreted
     as unsigned short. If the magic number is not a string, it
     may be an octal, hex, or decimal number. Octal numbers are
     specified by beginning them with a '0'. Hex numbers must
     begin with '0x'. Decimal numbers do not begin with '0' or
     '0x'. The description is a string that describes the type of
     file the magic number describes. It may contain one printf
     style specifier (such as '%d') which file will replace by
     the value of the magic number.

     The following are examples of magic number specification
     lines.  The first line describes a compacted text file (see
     compact(1) ), and the second describes a long format archive
     file (see ar(5) ).

          0    short          017777         Compacted text
          0    string         !<ARCH>        ASCII archive (long format)

     The format for a continuation line is:

          >offset    type    op    description

     Again, fields are separated by tabs.  The offset is the
     number of bits that should be checked in the next field,
     whose size is specified by the type field.  The op is one of
     '=', '>', or '<' followed by a number, the character 'x', or
     a string. If the op is '>' followed by a number, the
     corresponding data from the file must be a number that is



Printed 3/13/89                                                 1

MAGIC(5)                COMMAND REFERENCE                MAGIC(5)



     greater than the number given after the '>'. The characters
     '<' and '=' are similar in function and mean 'less than' and
     'equal to'.  The character 'x' means that any number will
     match.  If the type field is ``string'', the op field is a
     string to be matched.  The special string ``.*'' matches any
     string.  This is useful for printing null-terminated strings
     found at a known place in the file.  The description field
     is as before, except that a '%' specifier is replaced by the
     value compared against op field.

     The following lines show the description for an old style
     executable object file.

          0    short          0407      Old executable
          >16  long      >0        not stripped

     The '>16' in the second line implies that the next value to
     be checked starts at the 16th byte in the file. The '>0' in
     the op field specifies that the file matches the description
     ("not stripped") if the value is greater than 0.

     This is the description for a file which contains the magic
     number 0177512 followed by a null terminated string which is
     the file description.

          0    long      0177512        Described file
          >4   string         .*        -- %s

FILES
     /usr/lib/magic The magic number file

CAVEATS
     Most software that uses the magic file will not check the
     format of the file very carefully. See the manual page for
     file(1). This utility has the ability to check the format.

     The programs vi, ex, e, edit, and view can only handle 300
     magic numbers of type long and/or short.

SEE ALSO
     ex(1), file(1), more(1), and notmagic(3c).














Printed 3/13/89                                                 2

%%index%%
na:264,77;
de:341,3038;3715,1310;
fi:5025,121;
ca:5146,571;
se:5717,184;
%%index%%000000000106