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1 .\" $File: libmagic.man,v 1.34 2014/12/16 23:18:40 christos Exp $
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28 .Dd December 16, 2014
29 .Dt LIBMAGIC 3
30 .Os
31 .Sh NAME
32 .Nm magic_open ,
33 .Nm magic_close ,
34 .Nm magic_error ,
35 .Nm magic_errno ,
36 .Nm magic_descriptor ,
37 .Nm magic_buffer ,
38 .Nm magic_setflags ,
39 .Nm magic_check ,
40 .Nm magic_compile ,
41 .Nm magic_list ,
42 .Nm magic_load ,
43 .Nm magic_load_buffers ,
44 .Nm magic_setparam ,
45 .Nm magic_getparam ,
46 .Nm magic_version
47 .Nd Magic number recognition library
48 .Sh LIBRARY
49 .Lb libmagic
50 .Sh SYNOPSIS
51 .In magic.h
52 .Ft magic_t
53 .Fn magic_open "int flags"
54 .Ft void
55 .Fn magic_close "magic_t cookie"
56 .Ft const char *
57 .Fn magic_error "magic_t cookie"
58 .Ft int
59 .Fn magic_errno "magic_t cookie"
60 .Ft const char *
61 .Fn magic_descriptor "magic_t cookie" "int fd"
62 .Ft const char *
63 .Fn magic_file "magic_t cookie" "const char *filename"
64 .Ft const char *
65 .Fn magic_buffer "magic_t cookie" "const void *buffer" "size_t length"
66 .Ft int
67 .Fn magic_setflags "magic_t cookie" "int flags"
68 .Ft int
69 .Fn magic_check "magic_t cookie" "const char *filename"
70 .Ft int
71 .Fn magic_compile "magic_t cookie" "const char *filename"
72 .Ft int
73 .Fn magic_list "magic_t cookie" "const char *filename"
74 .Ft int
75 .Fn magic_load "magic_t cookie" "const char *filename"
76 .Ft int
77 .Fn magic_load_buffers "magic_t cookie" "void **buffers" "size_t *sizes" "size_t nbuffers"
78 .Ft int
79 .Fn magic_getparam "magic_t cookie" "int param" "void *value"
80 .Ft int
81 .Fn magic_setparam "magic_t cookie" "int param" "const void *value"
82 .Ft int
83 .Fn magic_version "void"
84 .Sh DESCRIPTION
85 These functions
86 operate on the magic database file
87 which is described
88 in
89 .Xr magic __FSECTION__ .
90 .Pp
91 The function
92 .Fn magic_open
93 creates a magic cookie pointer and returns it.
94 It returns
95 .Dv NULL
96 if there was an error allocating the magic cookie.
97 The
98 .Ar flags
99 argument specifies how the other magic functions should behave:
100 .Bl -tag -width MAGIC_COMPRESS
101 .It Dv MAGIC_NONE
102 No special handling.
103 .It Dv MAGIC_DEBUG
104 Print debugging messages to stderr.
105 .It Dv MAGIC_SYMLINK
106 If the file queried is a symlink, follow it.
107 .It Dv MAGIC_COMPRESS
108 If the file is compressed, unpack it and look at the contents.
109 .It Dv MAGIC_DEVICES
110 If the file is a block or character special device, then open the device
111 and try to look in its contents.
112 .It Dv MAGIC_MIME_TYPE
113 Return a MIME type string, instead of a textual description.
114 .It Dv MAGIC_MIME_ENCODING
115 Return a MIME encoding, instead of a textual description.
116 .It Dv MAGIC_MIME
117 A shorthand for MAGIC_MIME_TYPE | MAGIC_MIME_ENCODING.
118 .It Dv MAGIC_CONTINUE
119 Return all matches, not just the first.
120 .It Dv MAGIC_CHECK
121 Check the magic database for consistency and print warnings to stderr.
122 .It Dv MAGIC_PRESERVE_ATIME
123 On systems that support
124 .Xr utime 3
125 or
126 .Xr utimes 2 ,
127 attempt to preserve the access time of files analysed.
128 .It Dv MAGIC_RAW
129 Don't translate unprintable characters to a \eooo octal representation.
130 .It Dv MAGIC_ERROR
131 Treat operating system errors while trying to open files and follow symlinks
132 as real errors, instead of printing them in the magic buffer.
133 .It Dv MAGIC_APPLE
134 Return the Apple creator and type.
135 .It Dv MAGIC_NO_CHECK_APPTYPE
136 Don't check for
137 .Dv EMX
138 application type (only on EMX).
139 .It Dv MAGIC_NO_CHECK_CDF
140 Don't get extra information on MS Composite Document Files.
141 .It Dv MAGIC_NO_CHECK_COMPRESS
142 Don't look inside compressed files.
143 .It Dv MAGIC_NO_CHECK_ELF
144 Don't print ELF details.
145 .It Dv MAGIC_NO_CHECK_ENCODING
146 Don't check text encodings.
147 .It Dv MAGIC_NO_CHECK_SOFT
148 Don't consult magic files.
149 .It Dv MAGIC_NO_CHECK_TAR
150 Don't examine tar files.
151 .It Dv MAGIC_NO_CHECK_TEXT
152 Don't check for various types of text files.
153 .It Dv MAGIC_NO_CHECK_TOKENS
154 Don't look for known tokens inside ascii files.
155 .El
156 .Pp
157 The
158 .Fn magic_close
159 function closes the
160 .Xr magic __FSECTION__
161 database and deallocates any resources used.
162 .Pp
163 The
164 .Fn magic_error
165 function returns a textual explanation of the last error, or
166 .Dv NULL
167 if there was no error.
168 .Pp
169 The
170 .Fn magic_errno
171 function returns the last operating system error number
172 .Pq Xr errno 2
173 that was encountered by a system call.
174 .Pp
175 The
176 .Fn magic_file
177 function returns a textual description of the contents of the
178 .Ar filename
179 argument, or
180 .Dv NULL
181 if an error occurred.
182 If the
183 .Ar filename
184 is
185 .Dv NULL ,
186 then stdin is used.
187 .Pp
188 The
189 .Fn magic_descriptor
190 function returns a textual description of the contents of the
191 .Ar fd
192 argument, or
193 .Dv NULL
194 if an error occurred.
195 .Pp
196 The
197 .Fn magic_buffer
198 function returns a textual description of the contents of the
199 .Ar buffer
200 argument with
201 .Ar length
202 bytes size.
203 .Pp
204 The
205 .Fn magic_setflags
206 function sets the
207 .Ar flags
208 described above.
209 Note that using both MIME flags together can also
210 return extra information on the charset.
211 .Pp
212 The
213 .Fn magic_check
214 function can be used to check the validity of entries in the colon
215 separated database files passed in as
216 .Ar filename ,
217 or
218 .Dv NULL
219 for the default database.
220 It returns 0 on success and \-1 on failure.
221 .Pp
222 The
223 .Fn magic_compile
224 function can be used to compile the the colon
225 separated list of database files passed in as
226 .Ar filename ,
227 or
228 .Dv NULL
229 for the default database.
230 It returns 0 on success and \-1 on failure.
231 The compiled files created are named from the
232 .Xr basename 1
233 of each file argument with
234 .Dq .mgc
235 appended to it.
236 .Pp
237 The
238 .Fn magic_list
239 function dumps all magic entries in a human readable format,
240 dumping first the entries that are matched against binary files and then the
241 ones that match text files.
242 It takes and optional
243 .Fa filename
244 argument which is a colon separated list of database files, or
245 .Dv NULL
246 for the default database.
247 .Pp
248 The
249 .Fn magic_load
250 function must be used to load the the colon
251 separated list of database files passed in as
252 .Ar filename ,
253 or
254 .Dv NULL
255 for the default database file before any magic queries can performed.
256 .Pp
257 The default database file is named by the MAGIC environment variable.
258 If that variable is not set, the default database file name is __MAGIC__.
259 .Fn magic_load
260 adds
261 .Dq .mgc
262 to the database filename as appropriate.
263 .Pp
264 The
265 .Fn magic_load_buffers
266 function takes an array of size
267 .Fa nbuffers
268 of
269 .Fa buffers
270 with a respective size for each in the array of
271 .Fa sizes
272 loaded with the contents of the magic databases from the filesystem.
273 This function can be used in environment where the magic library does
274 not have direct access to the filesystem, but can access the magic
275 database via shared memory or other IPC means.
276 .Pp
277 The
278 .Fn magic_getparam
279 and
280 .Fn magic_setparam
281 allow getting and setting various limits related to the the magic
282 library.
283 .Bl -column "MAGIC_PARAM_ELF_PHNUM_MAX" "size_t" "Default" -offset indent
284 .It Sy "Parameter" Ta Sy "Type" Ta Sy "Default"
285 .It Li MAGIC_PARAM_INDIR_MAX Ta size_t Ta 15
286 .It Li MAGIC_PARAM_NAME_MAX Ta size_t Ta 30
287 .It Li MAGIC_PARAM_ELF_NOTES_MAX Ta size_t Ta 256
288 .It Li MAGIC_PARAM_ELF_PHNUM_MAX Ta size_t Ta 128
289 .It Li MAGIC_PARAM_ELF_SHNUM_MAX Ta size_t Ta 32768
290 .El
291 .Pp
292 The
293 .Dv MAGIC_PARAM_INDIR_RECURSION
294 parameter controls how many levels of recursion will be followed for
295 indirect magic entries.
296 .Pp
297 The
298 .Dv MAGIC_PARAM_NAME_RECURSION
299 parameter controls how many levels of recursion will be followed for
300 for name/use calls.
301 .Pp
302 The
303 .Dv MAGIC_PARAM_NAME_MAX
304 parameter controls the maximum number of calls for name/use.
305 .Pp
306 The
307 .Dv MAGIC_PARAM_NOTES_MAX
308 parameter controls how many ELF notes will be processed.
309 .Pp
310 The
311 .Dv MAGIC_PARAM_PHNUM_MAX
312 parameter controls how many ELF program sections will be processed.
313 .Pp
314 The
315 .Dv MAGIC_PARAM_SHNUM_MAX
316 parameter controls how many ELF sections will be processed.
317 .Pp
318 The
319 .Fn magic_version
320 command returns the version number of this library which is compiled into
321 the shared library using the constant
322 .Dv MAGIC_VERSION
323 from
324 .In magic.h .
325 This can be used by client programs to verify that the version they compile
326 against is the same as the version that they run against.
327 .Sh RETURN VALUES
328 The function
329 .Fn magic_open
330 returns a magic cookie on success and
331 .Dv NULL
332 on failure setting errno to an appropriate value.
333 It will set errno to
334 .Er EINVAL
335 if an unsupported value for flags was given.
336 The
337 .Fn magic_list ,
338 .Fn magic_load ,
339 .Fn magic_compile ,
340 and
341 .Fn magic_check
342 functions return 0 on success and \-1 on failure.
343 The
344 .Fn magic_buffer ,
345 .Fn magic_getpath ,
346 and
347 .Fn magic_file ,
348 functions return a string on success and
349 .Dv NULL
350 on failure.
351 The
352 .Fn magic_error
353 function returns a textual description of the errors of the above
354 functions, or
355 .Dv NULL
356 if there was no error.
357 The
358 .Fn magic_version
359 always returns the version number of the library.
360 Finally,
361 .Fn magic_setflags
362 returns \-1 on systems that don't support
363 .Xr utime 3 ,
364 or
365 .Xr utimes 2
366 when
367 .Dv MAGIC_PRESERVE_ATIME
368 is set.
369 .Sh FILES
370 .Bl -tag -width __MAGIC__.mgc -compact
371 .It Pa __MAGIC__
372 The non-compiled default magic database.
373 .It Pa __MAGIC__.mgc
374 The compiled default magic database.
375 .El
376 .Sh SEE ALSO
377 .Xr file __CSECTION__ ,
378 .Xr magic __FSECTION__
379 .Sh AUTHORS
380 .An M\(oans Rullg\(oard
381 Initial libmagic implementation, and configuration.
382 .An Christos Zoulas
383 API cleanup, error code and allocation handling.