4 .\" install as magic.4 on USG, magic.5 on V7 or Berkeley systems.
7 .Dt MAGIC 5 "Public Domain"
11 .Nd file command's magic number file
13 This manual page documents the format of the magic file as
16 command, version 4.12.
19 command identifies the type of a file using,
21 a test for whether the file begins with a certain
24 .Pa /usr/share/misc/magic
25 specifies what magic numbers are to be tested for,
26 what message to print if a particular magic number is found,
27 and additional information to extract from the file.
29 Each line of the file specifies a test to be performed.
30 A test compares the data starting at a particular offset
31 in the file with a 1-byte, 2-byte, or 4-byte numeric value or
33 If the test succeeds, a message is printed.
34 The line consists of the following fields:
35 .Bl -tag -width indent
37 A number specifying the offset, in bytes, into the file of the data
38 which is to be tested.
40 The type of the data to be tested.
41 The possible values are:
42 .Bl -tag -width indent
46 A two-byte value (on most systems) in this machine's native byte order.
48 A four-byte value (on most systems) in this machine's native byte order.
51 The string type specification can be optionally followed
55 flag compacts whitespace in the target, which must contain
56 at least one whitespace character.
59 consecutive blanks, the target needs at least
61 consecutive blanks to match.
64 flag treats every blank in the target as an optional blank.
67 flag, specifies case insensitive matching: lowercase characters
68 in the magic match both lower and upper case characters in the
69 targer, whereas upper case characters in the magic, only much
70 uppercase characters in the target.
72 A four-byte value interpreted as a
76 A four-byte value interpreted as a
78 date, but interpreted as
79 local time rather than UTC.
81 A two-byte value (on most systems) in big-endian byte order.
83 A four-byte value (on most systems) in big-endian byte order.
85 A four-byte value (on most systems) in big-endian byte order,
90 A two-byte value (on most systems) in little-endian byte order.
92 A four-byte value (on most systems) in little-endian byte order.
94 A four-byte value (on most systems) in little-endian byte order,
99 A four-byte value (on most systems) in little-endian byte order,
102 date, but interpreted as local time rather
107 The numeric types may optionally be followed by
110 to specify that the value is to be AND'ed with the
111 numeric value before any comparisons are done.
114 to the type indicates that ordered comparisons should be unsigned.
115 .Bl -tag -width indent
117 The value to be compared with the value from the file.
120 is specified in C form; if it is a string, it is specified as a C string
121 with the usual escapes permitted (e.g.\& \en for new-line).
124 may be preceded by a character indicating the operation to be performed.
127 to specify that the value from the file must equal the specified value,
129 to specify that the value from the file must be less than the specified
132 to specify that the value from the file must be greater than the specified
135 to specify that the value from the file must have set all of the bits
136 that are set in the specified value,
138 to specify that the value from the file must have clear any of the bits
139 that are set in the specified value, or
141 to specify that any value will match.
142 If the character is omitted,
146 Numeric values are specified in C form; e.g.\&
154 For string values, the byte string from the
155 file must match the specified byte string.
163 can be applied to strings.
164 The length used for matching is that of the string argument
166 This means that a line can match any string, and
167 then presumably print that string, by doing
169 (because all strings are greater than the null string).
171 The message to be printed if the comparison succeeds.
175 format specification, the value from the file (with any specified masking
176 performed) is printed using the message as the format string.
179 Some file formats contain additional information which is to be printed
180 along with the file type.
181 A line which begins with the character
183 indicates additional tests and messages to be printed.
186 on the line indicates the level of the test; a line with no
188 at the beginning is considered to be at level 0.
191 is under the control of the line at level
193 most closely preceding it in the magic file.
194 If the test on a line at level
196 succeeds, the tests specified in all the subsequent lines at level
198 are performed, and the messages printed if the tests succeed.
203 If the first character following the last
207 then the string after the parenthesis is interpreted as an indirect offset.
208 That means that the number after the parenthesis is used as an offset in
210 The value at that offset is read, and is used again as an offset
212 Indirect offsets are of the form:
213 .Em (x[.[bslBSL]][+\-][y]) .
216 is used as an offset in the file.
217 A byte, short or long is read at that offset
221 The capitalized types interpret the number as a big endian value, whereas
222 a small letter versions interpret the number as a little endian value.
223 To that number the value of
225 is added and the result is used as an offset in the file.
227 if one is not specified is long.
229 Sometimes you do not know the exact offset as this depends on the length of
231 You can specify an offset relative to the end of the
232 last uplevel field (of course this may only be done for sublevel tests, i.e.\&
235 Such a relative offset is specified using
237 as a prefix to the offset.
250 are system-dependent; perhaps they should be specified as a number
251 of bytes (2B, 4B, etc),
252 since the files being recognized typically come from
253 a system on which the lengths are invariant.
255 There is (currently) no support for specified-endian data to be used in
259 .Pa /usr/share/misc/magic
261 .Pa /usr/share/misc/magic.mgc
265 cd /usr/share/misc &&
274 .\" From: guy@sun.uucp (Guy Harris)
275 .\" Newsgroups: net.bugs.usg
276 .\" Subject: /etc/magic's format isn't well documented
277 .\" Message-ID: <2752@sun.uucp>
278 .\" Date: 3 Sep 85 08:19:07 GMT
279 .\" Organization: Sun Microsystems, Inc.
282 .\" Here's a manual page for the format accepted by the "file" made by adding
283 .\" the changes I posted to the S5R2 version.
285 .\" Modified for Ian Darwin's version of the file command.
286 .\" @(#)$Id: magic.man,v 1.27 2003/09/12 19:43:30 christos Exp $