1 .TH MAGIC __FSECTION__ "Public Domain"
2 .\" install as magic.4 on USG, magic.5 on V7 or Berkeley systems.
4 magic \- file command's magic number file
6 This manual page documents the format of the magic file as
8 .BR file (__CSECTION__)
9 command, version __VERSION__.
12 command identifies the type of a file using,
14 a test for whether the file begins with a certain
18 specifies what magic numbers are to be tested for,
19 what message to print if a particular magic number is found,
20 and additional information to extract from the file.
22 Each line of the file specifies a test to be performed.
23 A test compares the data starting at a particular offset
24 in the file with a 1-byte, 2-byte, or 4-byte numeric value or
26 If the test succeeds, a message is printed.
27 The line consists of the following fields:
28 .IP offset \w'message'u+2n
29 A number specifying the offset, in bytes, into the file of the data
30 which is to be tested.
32 The type of the data to be tested.
33 The possible values are:
35 .IP byte \w'message'u+2n
38 A two-byte value (on most systems) in this machine's native byte order.
40 A four-byte value (on most systems) in this machine's native byte order.
43 The string type specification can be optionally followed
45 The ``B'' flag compacts whitespace in the target, which must
46 contain at least one whitespace character.
49 consecutive blanks, the target needs at least
51 consecutive blanks to match.
52 The ``b'' flag treats every blank in the target as an optional blank.
53 Finally the ``c'' flag, specifies case insensitive matching: lowercase
54 characters in the magic match both lower and upper case characters in the
55 targer, whereas upper case characters in the magic, only much uppercase
56 characters in the target.
58 A four-byte value interpreted as a UNIX date.
60 A four-byte value interpreted as a UNIX-style date, but interpreted as
61 local time rather than UTC.
63 A two-byte value (on most systems) in big-endian byte order.
65 A four-byte value (on most systems) in big-endian byte order.
67 A four-byte value (on most systems) in big-endian byte order,
68 interpreted as a Unix date.
70 A two-byte value (on most systems) in little-endian byte order.
72 A four-byte value (on most systems) in little-endian byte order.
74 A four-byte value (on most systems) in little-endian byte order,
75 interpreted as a UNIX date.
77 A four-byte value (on most systems) in little-endian byte order,
78 interpreted as a UNIX-style date, but interpreted as local time rather
82 The numeric types may optionally be followed by
85 to specify that the value is to be AND'ed with the
86 numeric value before any comparisons are done.
89 to the type indicates that ordered comparisons should be unsigned.
91 The value to be compared with the value from the file.
94 is specified in C form; if it is a string, it is specified as a C string
95 with the usual escapes permitted (e.g. \en for new-line).
98 may be preceded by a character indicating the operation to be performed.
101 to specify that the value from the file must equal the specified value,
103 to specify that the value from the file must be less than the specified
106 to specify that the value from the file must be greater than the specified
109 to specify that the value from the file must have set all of the bits
110 that are set in the specified value,
112 to specify that the value from the file must have clear any of the bits
113 that are set in the specified value, or
115 to specify that any value will match.
116 If the character is omitted, it is assumed to be
119 Numeric values are specified in C form; e.g.
127 For string values, the byte string from the
128 file must match the specified byte string.
136 can be applied to strings.
137 The length used for matching is that of the string argument
139 This means that a line can match any string, and
140 then presumably print that string, by doing
142 (because all strings are greater than the null string).
144 The message to be printed if the comparison succeeds. If the string
147 format specification, the value from the file (with any specified masking
148 performed) is printed using the message as the format string.
150 Some file formats contain additional information which is to be printed
151 along with the file type.
152 A line which begins with the character
154 indicates additional tests and messages to be printed.
157 on the line indicates the level of the test; a line with no
159 at the beginning is considered to be at level 0.
162 is under the control of the line at level
164 most closely preceding it in the magic file.
165 If the test on a line at level
167 succeeds, the tests specified in all the subsequent lines at level
169 are performed, and the messages printed if the tests succeed.
170 The next line at level
173 If the first character following the last
177 then the string after the parenthesis is interpreted as an indirect offset.
178 That means that the number after the parenthesis is used as an offset in
180 The value at that offset is read, and is used again as an offset
182 Indirect offsets are of the form:
183 .BI (( x [.[bslBSL]][+\-][ y ]).
186 is used as an offset in the file. A byte, short or long is read at that offset
190 The capitalized types interpret the number as a big endian
191 value, whereas the small letter versions interpret the number as a little
193 To that number the value of
195 is added and the result is used as an offset in the file.
196 The default type if one is not specified is long.
198 Sometimes you do not know the exact offset as this depends on the length of
200 You can specify an offset relative to the end of the
201 last uplevel field (of course this may only be done for sublevel tests, i.e.
205 Such a relative offset is specified using
207 as a prefix to the offset.
220 are system-dependent; perhaps they should be specified as a number
221 of bytes (2B, 4B, etc),
222 since the files being recognized typically come from
223 a system on which the lengths are invariant.
225 There is (currently) no support for specified-endian data to be used in
228 .BR file (__CSECTION__)
229 \- the command that reads this file.
231 .\" From: guy@sun.uucp (Guy Harris)
232 .\" Newsgroups: net.bugs.usg
233 .\" Subject: /etc/magic's format isn't well documented
234 .\" Message-ID: <2752@sun.uucp>
235 .\" Date: 3 Sep 85 08:19:07 GMT
236 .\" Organization: Sun Microsystems, Inc.
239 .\" Here's a manual page for the format accepted by the "file" made by adding
240 .\" the changes I posted to the S5R2 version.
242 .\" Modified for Ian Darwin's version of the file command.
243 .\" @(#)$Id: magic.man,v 1.27 2003/09/12 19:43:30 christos Exp $