2 .\" $FreeBSD: src/usr.bin/file/magic.5,v 1.11.2.8 2003/03/16 04:47:04 obrien Exp $
3 .\" $DragonFly: src/usr.bin/file/Attic/magic.5,v 1.3 2006/02/17 19:39:04 swildner Exp $
5 .\" install as magic.4 on USG, magic.5 on V7 or Berkeley systems.
8 .Dt MAGIC 5 "Public Domain"
12 .Nd file command's magic number file
14 This manual page documents the format of the magic file as
17 command, version 3.41.
20 command identifies the type of a file using,
22 a test for whether the file begins with a certain
25 .Pa /usr/share/misc/magic
26 specifies what magic numbers are to be tested for,
27 what message to print if a particular magic number is found,
28 and additional information to extract from the file.
30 Each line of the file specifies a test to be performed.
31 A test compares the data starting at a particular offset
32 in the file with a 1-byte, 2-byte, or 4-byte numeric value or
34 If the test succeeds, a message is printed.
35 The line consists of the following fields:
36 .Bl -tag -width indent
38 A number specifying the offset, in bytes, into the file of the data
39 which is to be tested.
41 The type of the data to be tested.
42 The possible values are:
43 .Bl -tag -width indent
47 A two-byte value (on most systems) in this machine's native byte order.
49 A four-byte value (on most systems) in this machine's native byte order.
52 The string type specification can be optionally followed
56 flag compacts whitespace in the target, which must contain
57 at least one whitespace character.
58 If the magic has "n" consecutive blanks, the target needs
59 at least "n" consecutive blanks to match.
62 flag treats every blank in the target as an optional blank.
65 flag, specifies case insensitive matching: lowercase characters
66 in the magic match both lower and upper case characters in the
67 targer, whereas upper case characters in the magic, only much
68 uppercase characters in the target.
70 A four-byte value interpreted as a
74 A four-byte value interpreted as a
76 date, but interpreted as
77 local time rather than UTC.
79 A two-byte value (on most systems) in big-endian byte order.
81 A four-byte value (on most systems) in big-endian byte order.
83 A four-byte value (on most systems) in big-endian byte order,
88 A two-byte value (on most systems) in little-endian byte order.
90 A four-byte value (on most systems) in little-endian byte order.
92 A four-byte value (on most systems) in little-endian byte order,
97 A four-byte value (on most systems) in little-endian byte order,
100 date, but interpreted as local time rather
105 The numeric types may optionally be followed by
108 to specify that the value is to be AND'ed with the
109 numeric value before any comparisons are done. Prepending a
111 to the type indicates that ordered comparisons should be unsigned.
112 .Bl -tag -width indent
114 The value to be compared with the value from the file. If the type is
116 is specified in C form; if it is a string, it is specified as a C string
117 with the usual escapes permitted (e.g. \en for new-line).
120 may be preceded by a character indicating the operation to be performed.
123 to specify that the value from the file must equal the specified value,
125 to specify that the value from the file must be less than the specified
128 to specify that the value from the file must be greater than the specified
131 to specify that the value from the file must have set all of the bits
132 that are set in the specified value,
134 to specify that the value from the file must have clear any of the bits
135 that are set in the specified value, or
137 to specify that any value will match.
138 If the character is omitted,
142 Numeric values are specified in C form; e.g.\&
150 For string values, the byte string from the
151 file must match the specified byte string.
159 can be applied to strings.
160 The length used for matching is that of the string argument
161 in the magic file. This means that a line can match any string, and
162 then presumably print that string, by doing
164 (because all strings are greater than the null string).
166 The message to be printed if the comparison succeeds. If the string
169 format specification, the value from the file (with any specified masking
170 performed) is printed using the message as the format string.
173 Some file formats contain additional information which is to be printed
174 along with the file type. A line which begins with the character
176 indicates additional tests and messages to be printed. The number of
178 on the line indicates the level of the test; a line with no
180 at the beginning is considered to be at level 0.
183 is under the control of the line at level
185 most closely preceding it in the magic file.
186 If the test on a line at level
188 succeeds, the tests specified in all the subsequent lines at level
190 are performed, and the messages printed if the tests succeed. The next
194 If the first character following the last
198 then the string after the parenthesis is interpreted as an indirect offset.
199 That means that the number after the parenthesis is used as an offset in
201 The value at that offset is read, and is used again as an offset
203 Indirect offsets are of the form:
204 .Em (x[.[bslBSL]][+-][y]) .
207 is used as an offset in the file.
208 A byte, short or long is read at that offset
212 The capitalized types interpret the number as a big endian value, whereas
213 a small letter versions interpret the number as a little endian value.
214 To that number the value of
216 is added and the result is used as an offset in the file.
218 if one is not specified is long.
220 Sometimes you do not know the exact offset as this depends on the length of
222 You can specify an offset relative to the end of the
223 last uplevel field (of course this may only be done for sublevel tests, i.e.\&
226 Such a relative offset is specified using
228 as a prefix to the offset.
243 are system-dependent; perhaps they should be specified as a number
244 of bytes (2B, 4B, etc),
245 since the files being recognized typically come from
246 a system on which the lengths are invariant.
248 There is (currently) no support for specified-endian data to be used in
251 .\" From: guy@sun.uucp (Guy Harris)
252 .\" Newsgroups: net.bugs.usg
253 .\" Subject: /etc/magic's format isn't well documented
254 .\" Message-ID: <2752@sun.uucp>
255 .\" Date: 3 Sep 85 08:19:07 GMT
256 .\" Organization: Sun Microsystems, Inc.
259 .\" Here's a manual page for the format accepted by the "file" made by adding
260 .\" the changes I posted to the S5R2 version.
262 .\" Modified for Ian Darwin's version of the file command.
263 .\" @(#)$Id: magic.man,v 1.21 2003/02/27 20:47:46 christos Exp $