1.\" $NetBSD: libmagic.3,v 1.17 2017/10/22 11:17:39 abhinav Exp $ 2.\" 3.\" $File: libmagic.man,v 1.41 2017/05/23 21:54:07 christos Exp $ 4.\" 5.\" Copyright (c) Christos Zoulas 2003. 6.\" All Rights Reserved. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice immediately at the beginning of the file, without modification, 13.\" this list of conditions, and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 22.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd May 23, 2017 31.Dt LIBMAGIC 3 32.Os 33.Sh NAME 34.Nm magic_open , 35.Nm magic_close , 36.Nm magic_error , 37.Nm magic_errno , 38.Nm magic_descriptor , 39.Nm magic_file , 40.Nm magic_buffer , 41.Nm magic_getflags , 42.Nm magic_setflags , 43.Nm magic_check , 44.Nm magic_compile , 45.Nm magic_list , 46.Nm magic_load , 47.Nm magic_load_buffers , 48.Nm magic_setparam , 49.Nm magic_getparam , 50.Nm magic_version 51.Nd Magic number recognition library 52.Sh LIBRARY 53.Lb libmagic 54.Sh SYNOPSIS 55.In magic.h 56.Ft magic_t 57.Fn magic_open "int flags" 58.Ft void 59.Fn magic_close "magic_t cookie" 60.Ft const char * 61.Fn magic_error "magic_t cookie" 62.Ft int 63.Fn magic_errno "magic_t cookie" 64.Ft const char * 65.Fn magic_descriptor "magic_t cookie" "int fd" 66.Ft const char * 67.Fn magic_file "magic_t cookie" "const char *filename" 68.Ft const char * 69.Fn magic_buffer "magic_t cookie" "const void *buffer" "size_t length" 70.Ft int 71.Fn magic_getflags "magic_t cookie" 72.Ft int 73.Fn magic_setflags "magic_t cookie" "int flags" 74.Ft int 75.Fn magic_check "magic_t cookie" "const char *filename" 76.Ft int 77.Fn magic_compile "magic_t cookie" "const char *filename" 78.Ft int 79.Fn magic_list "magic_t cookie" "const char *filename" 80.Ft int 81.Fn magic_load "magic_t cookie" "const char *filename" 82.Ft int 83.Fn magic_load_buffers "magic_t cookie" "void **buffers" "size_t *sizes" "size_t nbuffers" 84.Ft int 85.Fn magic_getparam "magic_t cookie" "int param" "void *value" 86.Ft int 87.Fn magic_setparam "magic_t cookie" "int param" "const void *value" 88.Ft int 89.Fn magic_version "void" 90.Sh DESCRIPTION 91These functions 92operate on the magic database file 93which is described 94in 95.Xr magic 5 . 96.Pp 97The function 98.Fn magic_open 99creates a magic cookie pointer and returns it. 100It returns 101.Dv NULL 102if there was an error allocating the magic cookie. 103The 104.Ar flags 105argument specifies how the other magic functions should behave: 106.Bl -tag -width MAGIC_COMPRESS 107.It Dv MAGIC_NONE 108No special handling. 109.It Dv MAGIC_DEBUG 110Print debugging messages to stderr. 111.It Dv MAGIC_SYMLINK 112If the file queried is a symlink, follow it. 113.It Dv MAGIC_COMPRESS 114If the file is compressed, unpack it and look at the contents. 115.It Dv MAGIC_DEVICES 116If the file is a block or character special device, then open the device 117and try to look in its contents. 118.It Dv MAGIC_MIME_TYPE 119Return a MIME type string, instead of a textual description. 120.It Dv MAGIC_MIME_ENCODING 121Return a MIME encoding, instead of a textual description. 122.It Dv MAGIC_MIME 123A shorthand for MAGIC_MIME_TYPE | MAGIC_MIME_ENCODING. 124.It Dv MAGIC_CONTINUE 125Return all matches, not just the first. 126.It Dv MAGIC_CHECK 127Check the magic database for consistency and print warnings to stderr. 128.It Dv MAGIC_PRESERVE_ATIME 129On systems that support 130.Xr utime 3 131or 132.Xr utimes 2 , 133attempt to preserve the access time of files analysed. 134.It Dv MAGIC_RAW 135Don't translate unprintable characters to a \eooo octal representation. 136.It Dv MAGIC_ERROR 137Treat operating system errors while trying to open files and follow symlinks 138as real errors, instead of printing them in the magic buffer. 139.It Dv MAGIC_APPLE 140Return the Apple creator and type. 141.It Dv MAGIC_EXTENSION 142Return a slash-separated list of extensions for this file type. 143.It Dv MAGIC_COMPRESS_TRANSP 144Don't report on compression, only report about the uncompressed data. 145.It Dv MAGIC_NO_CHECK_APPTYPE 146Don't check for 147.Dv EMX 148application type (only on EMX). 149.It Dv MAGIC_NO_CHECK_CDF 150Don't get extra information on MS Composite Document Files. 151.It Dv MAGIC_NO_CHECK_COMPRESS 152Don't look inside compressed files. 153.It Dv MAGIC_NO_CHECK_ELF 154Don't print ELF details. 155.It Dv MAGIC_NO_CHECK_ENCODING 156Don't check text encodings. 157.It Dv MAGIC_NO_CHECK_SOFT 158Don't consult magic files. 159.It Dv MAGIC_NO_CHECK_TAR 160Don't examine tar files. 161.It Dv MAGIC_NO_CHECK_TEXT 162Don't check for various types of text files. 163.It Dv MAGIC_NO_CHECK_TOKENS 164Don't look for known tokens inside ascii files. 165.El 166.Pp 167The 168.Fn magic_close 169function closes the 170.Xr magic 5 171database and deallocates any resources used. 172.Pp 173The 174.Fn magic_error 175function returns a textual explanation of the last error, or 176.Dv NULL 177if there was no error. 178.Pp 179The 180.Fn magic_errno 181function returns the last operating system error number 182.Pq Xr errno 2 183that was encountered by a system call. 184.Pp 185The 186.Fn magic_file 187function returns a textual description of the contents of the 188.Ar filename 189argument, or 190.Dv NULL 191if an error occurred. 192If the 193.Ar filename 194is 195.Dv NULL , 196then stdin is used. 197.Pp 198The 199.Fn magic_descriptor 200function returns a textual description of the contents of the 201.Ar fd 202argument, or 203.Dv NULL 204if an error occurred. 205.Pp 206The 207.Fn magic_buffer 208function returns a textual description of the contents of the 209.Ar buffer 210argument with 211.Ar length 212bytes size. 213.Pp 214The 215.Fn magic_getflags 216functions returns a value representing current 217.Ar flags 218set. 219.Pp 220The 221.Fn magic_setflags 222function sets the 223.Ar flags 224described above. 225Note that using both MIME flags together can also 226return extra information on the charset. 227.Pp 228The 229.Fn magic_check 230function can be used to check the validity of entries in the colon 231separated database files passed in as 232.Ar filename , 233or 234.Dv NULL 235for the default database. 236It returns 0 on success and \-1 on failure. 237.Pp 238The 239.Fn magic_compile 240function can be used to compile the colon 241separated list of database files passed in as 242.Ar filename , 243or 244.Dv NULL 245for the default database. 246It returns 0 on success and \-1 on failure. 247The compiled files created are named from the 248.Xr basename 1 249of each file argument with 250.Dq .mgc 251appended to it. 252.Pp 253The 254.Fn magic_list 255function dumps all magic entries in a human readable format, 256dumping first the entries that are matched against binary files and then the 257ones that match text files. 258It takes and optional 259.Fa filename 260argument which is a colon separated list of database files, or 261.Dv NULL 262for the default database. 263.Pp 264The 265.Fn magic_load 266function must be used to load the colon 267separated list of database files passed in as 268.Ar filename , 269or 270.Dv NULL 271for the default database file before any magic queries can performed. 272.Pp 273The default database file is named by the MAGIC environment variable. 274If that variable is not set, the default database file name is 275.Pa /usr/share/misc/magic . 276.Fn magic_load 277adds 278.Dq .mgc 279to the database filename as appropriate. 280.Pp 281The 282.Fn magic_load_buffers 283function takes an array of size 284.Fa nbuffers 285of 286.Fa buffers 287with a respective size for each in the array of 288.Fa sizes 289loaded with the contents of the magic databases from the filesystem. 290This function can be used in environment where the magic library does 291not have direct access to the filesystem, but can access the magic 292database via shared memory or other IPC means. 293.Pp 294The 295.Fn magic_getparam 296and 297.Fn magic_setparam 298allow getting and setting various limits related to the magic 299library. 300.Bl -column "MAGIC_PARAM_ELF_PHNUM_MAX" "size_t" "Default" -offset indent 301.It Sy "Parameter" Ta Sy "Type" Ta Sy "Default" 302.It Li MAGIC_PARAM_INDIR_MAX Ta size_t Ta 15 303.It Li MAGIC_PARAM_NAME_MAX Ta size_t Ta 30 304.It Li MAGIC_PARAM_ELF_NOTES_MAX Ta size_t Ta 256 305.It Li MAGIC_PARAM_ELF_PHNUM_MAX Ta size_t Ta 128 306.It Li MAGIC_PARAM_ELF_SHNUM_MAX Ta size_t Ta 32768 307.It Li MAGIC_PARAM_REGEX_MAX Ta size_t Ta 8192 308.It Li MAGIC_PARAM_BYTES_MAX Ta size_t Ta 1048576 309.El 310.Pp 311The 312.Dv MAGIC_PARAM_INDIR_RECURSION 313parameter controls how many levels of recursion will be followed for 314indirect magic entries. 315.Pp 316The 317.Dv MAGIC_PARAM_NAME_RECURSION 318parameter controls how many levels of recursion will be followed for 319for name/use calls. 320.Pp 321The 322.Dv MAGIC_PARAM_NAME_MAX 323parameter controls the maximum number of calls for name/use. 324.Pp 325The 326.Dv MAGIC_PARAM_NOTES_MAX 327parameter controls how many ELF notes will be processed. 328.Pp 329The 330.Dv MAGIC_PARAM_PHNUM_MAX 331parameter controls how many ELF program sections will be processed. 332.Pp 333The 334.Dv MAGIC_PARAM_SHNUM_MAX 335parameter controls how many ELF sections will be processed. 336.Pp 337The 338.Fn magic_version 339command returns the version number of this library which is compiled into 340the shared library using the constant 341.Dv MAGIC_VERSION 342from 343.In magic.h . 344This can be used by client programs to verify that the version they compile 345against is the same as the version that they run against. 346.Sh RETURN VALUES 347The function 348.Fn magic_open 349returns a magic cookie on success and 350.Dv NULL 351on failure setting errno to an appropriate value. 352It will set errno to 353.Er EINVAL 354if an unsupported value for flags was given. 355The 356.Fn magic_list , 357.Fn magic_load , 358.Fn magic_compile , 359and 360.Fn magic_check 361functions return 0 on success and \-1 on failure. 362The 363.Fn magic_buffer , 364.Fn magic_getpath , 365and 366.Fn magic_file , 367functions return a string on success and 368.Dv NULL 369on failure. 370The 371.Fn magic_error 372function returns a textual description of the errors of the above 373functions, or 374.Dv NULL 375if there was no error. 376The 377.Fn magic_version 378always returns the version number of the library. 379Finally, 380.Fn magic_setflags 381returns \-1 on systems that don't support 382.Xr utime 3 , 383or 384.Xr utimes 2 385when 386.Dv MAGIC_PRESERVE_ATIME 387is set. 388.Sh FILES 389.Bl -tag -width /usr/share/misc/magic.mgc -compact 390.It Pa /usr/share/misc/magic 391The non-compiled default magic database. 392.It Pa /usr/share/misc/magic.mgc 393The compiled default magic database. 394.El 395.Sh SEE ALSO 396.Xr file 1 , 397.Xr magic 5 398.Sh AUTHORS 399.An M\(oans Rullg\(oard 400Initial libmagic implementation, and configuration. 401.An Christos Zoulas 402API cleanup, error code and allocation handling. 403