libmagic.man 6.5 KB

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  1. .\"
  2. .\" Copyright (c) Christos Zoulas 2003.
  3. .\" All Rights Reserved.
  4. .\"
  5. .\" Redistribution and use in source and binary forms, with or without
  6. .\" modification, are permitted provided that the following conditions
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  9. .\" notice immediately at the beginning of the file, without modification,
  10. .\" this list of conditions, and the following disclaimer.
  11. .\" 2. Redistributions in binary form must reproduce the above copyright
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  13. .\" documentation and/or other materials provided with the distribution.
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  15. .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  16. .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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  27. .Dd November 15, 2006
  28. .Dt MAGIC 3
  29. .Os
  30. .Sh NAME
  31. .Nm magic_open ,
  32. .Nm magic_close ,
  33. .Nm magic_error ,
  34. .Nm magic_file ,
  35. .Nm magic_buffer ,
  36. .Nm magic_setflags ,
  37. .Nm magic_check ,
  38. .Nm magic_compile ,
  39. .Nm magic_load
  40. .Nd Magic number recognition library.
  41. .Sh LIBRARY
  42. .Lb libmagic
  43. .Sh SYNOPSIS
  44. .In magic.h
  45. .Ft magic_t
  46. .Fn magic_open "int flags"
  47. .Ft void
  48. .Fn magic_close "magic_t cookie"
  49. .Ft const char *
  50. .Fn magic_error "magic_t cookie"
  51. .Ft int
  52. .Fn magic_errno "magic_t cookie"
  53. .Ft const char *
  54. .Fn magic_file "magic_t cookie, const char *filename"
  55. .Ft const char *
  56. .Fn magic_buffer "magic_t cookie, const void *buffer, size_t length"
  57. .Ft int
  58. .Fn magic_setflags "magic_t cookie, int flags"
  59. .Ft int
  60. .Fn magic_check "magic_t cookie, const char *filename"
  61. .Ft int
  62. .Fn magic_compile "magic_t cookie, const char *filename"
  63. .Ft int
  64. .Fn magic_load "magic_t cookie, const char *filename"
  65. .Sh DESCRIPTION
  66. These functions
  67. operate on the magic database file
  68. which is described
  69. in
  70. .Xr magic __FSECTION__ .
  71. .Pp
  72. The function
  73. .Fn magic_open
  74. creates a magic cookie pointer and returns it. It returns NULL if
  75. there was an error allocating the magic cookie. The
  76. .Ar flags
  77. argument specifies how the other magic functions should behave:
  78. .Bl -tag -width MAGIC_COMPRESS
  79. .It Dv MAGIC_NONE
  80. No special handling.
  81. .It Dv MAGIC_DEBUG
  82. Print debugging messages to stderr.
  83. .It Dv MAGIC_SYMLINK
  84. If the file queried is a symlink, follow it.
  85. .It Dv MAGIC_COMPRESS
  86. If the file is compressed, unpack it and look at the contents.
  87. .It Dv MAGIC_DEVICES
  88. If the file is a block or character special device, then open the device
  89. and try to look in its contents.
  90. .It Dv MAGIC_MIME
  91. Return a mime string, instead of a textual description.
  92. .It Dv MAGIC_CONTINUE
  93. Return all matches, not just the first.
  94. .It Dv MAGIC_CHECK
  95. Check the magic database for consistency and print warnings to stderr.
  96. .It Dv MAGIC_PRESERVE_ATIME
  97. On systems that support
  98. .Xr utime 2
  99. or
  100. .Xr utimes 2 ,
  101. attempt to preserve the access time of files analyzed.
  102. .It Dv MAGIC_RAW
  103. Don't translate unprintable characters to a \eooo octal representation.
  104. .It Dv MAGIC_ERROR
  105. Treat operating system errors while trying to open files and follow symlinks
  106. as real errors, instead of printing them in the magic buffer.
  107. .El
  108. .Pp
  109. The
  110. .Fn magic_close
  111. function closes the
  112. .Xr magic __FSECTION__
  113. database and deallocates any resources used.
  114. .Pp
  115. The
  116. .Fn magic_error
  117. function returns a textual explanation of the last error, or NULL if there was
  118. no error.
  119. .Pp
  120. The
  121. .Fn magic_errno
  122. function returns the last operating system error number
  123. .Pq .Xr errno 2
  124. that was encountered by a system call.
  125. .Pp
  126. The
  127. .Fn magic_file
  128. function returns a textual description of the contents of the
  129. .Ar filename
  130. argument, or NULL if an error occurred.
  131. If the
  132. .Ar filename
  133. is NULL, then stdin is used.
  134. .Pp
  135. The
  136. .Fn magic_buffer
  137. function returns a textual description of the contents of the
  138. .Ar buffer
  139. argument with
  140. .Ar length
  141. bytes size.
  142. .Pp
  143. The
  144. .Fn magic_setflags
  145. function, sets the
  146. .Ar flags
  147. described above.
  148. .Pp
  149. The
  150. .Fn magic_check
  151. function can be used to check the validity of entries in the colon
  152. separated database files passed in as
  153. .Ar filename ,
  154. or NULL for the default database. It returns 0 on success and -1 on
  155. failure.
  156. .Pp
  157. The
  158. .Fn magic_compile
  159. function can be used to compile the the colon
  160. separated list of database files passed in as
  161. .Ar filename ,
  162. or NULL for the default database. It returns 0 on success and -1 on
  163. failure. The compiled files created are named from the
  164. .Xr basename 1
  165. of each file argument with ".mgc" appended to it.
  166. .Pp
  167. The
  168. .Fn magic_load
  169. function must be used to load the the colon
  170. separated list of database files passed in as
  171. .Ar filename ,
  172. or NULL for the default database file
  173. before any magic queries can performed.
  174. .Pp
  175. The default database file is named by the MAGIC environment variable. If
  176. that variable is not set, the default database file name is __MAGIC__.
  177. .Pp
  178. .Fn magic_load
  179. adds ".mime" and/or ".mgc" to the database filename as appropriate.
  180. .Sh RETURN VALUES
  181. The function
  182. .Fn magic_open
  183. returns a magic cookie on success and NULL on failure setting errno to
  184. an appropriate value. It will set errno to EINVAL if an unsupported
  185. value for flags was given.
  186. The
  187. .Fn magic_load ,
  188. .Fn magic_compile ,
  189. and
  190. .Fn magic_check
  191. functions return 0 on success and -1 on failure.
  192. The
  193. .Fn magic_file ,
  194. and
  195. .Fn magic_buffer
  196. functions return a string on success and NULL on failure. The
  197. .Fn magic_error
  198. function returns a textual description of the errors of the above
  199. functions, or NULL if there was no error.
  200. Finally,
  201. .Fn magic_setflags
  202. returns -1 on systems that don't support
  203. .Xr utime 2 ,
  204. or
  205. .Xr utimes 2
  206. when
  207. .Dv MAGIC_PRESERVE_ATIME
  208. is set.
  209. .Sh FILES
  210. .Bl -tag -width __MAGIC__.mime.mgc -compact
  211. .It Pa __MAGIC__.mime
  212. The non-compiled default magic mime database.
  213. .It Pa __MAGIC__.mime.mgc
  214. The compiled default magic mime database.
  215. .It Pa __MAGIC__
  216. The non-compiled default magic database.
  217. .It Pa __MAGIC__.mgc
  218. The compiled default magic database.
  219. .El
  220. .Sh SEE ALSO
  221. .Xr file __CSECTION__ ,
  222. .Xr magic __FSECTION__
  223. .Sh AUTHORS
  224. Måns Rullgård Initial libmagic implementation,
  225. and configuration.
  226. Christos Zoulas API cleanup, error code and allocation handling.