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 by /[Bbc]*.
44 The ``B'' flag compacts whitespace in the target, which must
45 contain at least one whitespace character.
46 If the magic has "n" consecutive
47 blanks, the target needs at least "n" consecutive blanks to match.
48 The ``b'' flag treats every blank in the target as an optional blank.
50 flag, specifies case insensitive matching: lowercase characters in the magic
51 match both lower and upper case characters in the targer, whereas upper case
52 characters in the magic, only much uppercase characters in the target.
54 A four-byte value interpreted as a UNIX date.
56 A four-byte value interpreted as a UNIX-style date, but interpreted as
57 local time rather than UTC.
59 A two-byte value (on most systems) in big-endian byte order.
61 A four-byte value (on most systems) in big-endian byte order.
63 A four-byte value (on most systems) in big-endian byte order,
64 interpreted as a unix date.
66 A two-byte value (on most systems) in little-endian byte order.
68 A four-byte value (on most systems) in little-endian byte order.
70 A four-byte value (on most systems) in little-endian byte order,
71 interpreted as a UNIX date.
73 A four-byte value (on most systems) in little-endian byte order,
74 interpreted as a UNIX-style date, but interpreted as local time rather
78 The numeric types may optionally be followed by
81 to specify that the value is to be AND'ed with the
82 numeric value before any comparisons are done.
85 to the type indicates that ordered comparisons should be unsigned.
87 The value to be compared with the value from the file.
88 If the type is numeric, this value
89 is specified in C form; if it is a string, it is specified as a C string
90 with the usual escapes permitted (e.g. \en for new-line).
93 may be preceded by a character indicating the operation to be performed.
96 to specify that the value from the file must equal the specified value,
98 to specify that the value from the file must be less than the specified
101 to specify that the value from the file must be greater than the specified
104 to specify that the value from the file must have set all of the bits
105 that are set in the specified value,
107 to specify that the value from the file must have clear any of the bits
108 that are set in the specified value, or
110 to specify that any value will match.
111 If the character is omitted, it is assumed to be
114 Numeric values are specified in C form; e.g.
122 For string values, the byte string from the
123 file must match the specified byte string.
131 can be applied to strings.
132 The length used for matching is that of the string argument
134 This means that a line can match any string, and
135 then presumably print that string, by doing
137 (because all strings are greater than the null string).
139 The message to be printed if the comparison succeeds.
140 If the string contains a
142 format specification, the value from the file (with any specified masking
143 performed) is printed using the message as the format string.
145 Some file formats contain additional information which is to be printed
146 along with the file type.
147 A line which begins with the character
149 indicates additional tests and messages to be printed.
152 on the line indicates the level of the test; a line with no
154 at the beginning is considered to be at level 0.
157 is under the control of the line at level
159 most closely preceding it in the magic file.
160 If the test on a line at level
162 succeeds, the tests specified in all the subsequent lines at level
164 are performed, and the messages printed if the tests succeed.
165 The next line at level
168 If the first character following the last
172 then the string after the parenthesis is interpreted as an indirect offset.
173 That means that the number after the parenthesis is used as an offset in
175 The value at that offset is read, and is used again as an offset
177 Indirect offsets are of the form:
178 .BI (( x [.[bslBSL]][+-][ y ]).
181 is used as an offset in the file.
182 A byte, short or long is read at that offset depending on the
185 The capitalized types interpret the number as a big endian
186 value, whereas the small letter versions interpret the number as a little
188 To that number the value of
190 is added and the result is used as an offset in the file.
191 The default type if one is not specified is long.
193 Sometimes you do not know the exact offset as this depends on the length of
195 You can specify an offset relative to the end of the
196 last uplevel field (of course this may only be done for sublevel tests, i.e.
200 Such a relative offset is specified using
202 as a prefix to the offset.
215 are system-dependent; perhaps they should be specified as a number
216 of bytes (2B, 4B, etc),
217 since the files being recognized typically come from
218 a system on which the lengths are invariant.
220 There is (currently) no support for specified-endian data to be used in
223 .BR file (__CSECTION__)
224 \- the command that reads this file.
226 .\" From: guy@sun.uucp (Guy Harris)
227 .\" Newsgroups: net.bugs.usg
228 .\" Subject: /etc/magic's format isn't well documented
229 .\" Message-ID: \*[Lt]2752@sun.uucp\*[Gt]
230 .\" Date: 3 Sep 85 08:19:07 GMT
231 .\" Organization: Sun Microsystems, Inc.
234 .\" Here's a manual page for the format accepted by the "file" made by adding
235 .\" the changes I posted to the S5R2 version.
237 .\" Modified for Ian Darwin's version of the file command.
238 .\" @(#)$Id: magic.man,v 1.21 2003/02/27 20:47:46 christos Exp $