1.\" $File: libmagic.man,v 1.44 2018/09/09 20:33:28 christos Exp $ 2.\" 3.\" Copyright (c) Christos Zoulas 2003, 2018. 4.\" All Rights Reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice immediately at the beginning of the file, without modification, 11.\" this list of conditions, and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 20.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd August 18, 2018 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_getflags , 39.Nm magic_setflags , 40.Nm magic_check , 41.Nm magic_compile , 42.Nm magic_list , 43.Nm magic_load , 44.Nm magic_load_buffers , 45.Nm magic_setparam , 46.Nm magic_getparam , 47.Nm magic_version 48.Nd Magic number recognition library 49.Sh LIBRARY 50.Lb libmagic 51.Sh SYNOPSIS 52.In magic.h 53.Ft magic_t 54.Fn magic_open "int flags" 55.Ft void 56.Fn magic_close "magic_t cookie" 57.Ft const char * 58.Fn magic_error "magic_t cookie" 59.Ft int 60.Fn magic_errno "magic_t cookie" 61.Ft const char * 62.Fn magic_descriptor "magic_t cookie" "int fd" 63.Ft const char * 64.Fn magic_file "magic_t cookie" "const char *filename" 65.Ft const char * 66.Fn magic_buffer "magic_t cookie" "const void *buffer" "size_t length" 67.Ft int 68.Fn magic_getflags "magic_t cookie" 69.Ft int 70.Fn magic_setflags "magic_t cookie" "int flags" 71.Ft int 72.Fn magic_check "magic_t cookie" "const char *filename" 73.Ft int 74.Fn magic_compile "magic_t cookie" "const char *filename" 75.Ft int 76.Fn magic_list "magic_t cookie" "const char *filename" 77.Ft int 78.Fn magic_load "magic_t cookie" "const char *filename" 79.Ft int 80.Fn magic_load_buffers "magic_t cookie" "void **buffers" "size_t *sizes" "size_t nbuffers" 81.Ft int 82.Fn magic_getparam "magic_t cookie" "int param" "void *value" 83.Ft int 84.Fn magic_setparam "magic_t cookie" "int param" "const void *value" 85.Ft int 86.Fn magic_version "void" 87.Sh DESCRIPTION 88These functions 89operate on the magic database file 90which is described 91in 92.Xr magic __FSECTION__ . 93.Pp 94The function 95.Fn magic_open 96creates a magic cookie pointer and returns it. 97It returns 98.Dv NULL 99if there was an error allocating the magic cookie. 100The 101.Ar flags 102argument specifies how the other magic functions should behave: 103.Bl -tag -width MAGIC_COMPRESS 104.It Dv MAGIC_NONE 105No special handling. 106.It Dv MAGIC_DEBUG 107Print debugging messages to stderr. 108.It Dv MAGIC_SYMLINK 109If the file queried is a symlink, follow it. 110.It Dv MAGIC_COMPRESS 111If the file is compressed, unpack it and look at the contents. 112.It Dv MAGIC_DEVICES 113If the file is a block or character special device, then open the device 114and try to look in its contents. 115.It Dv MAGIC_MIME_TYPE 116Return a MIME type string, instead of a textual description. 117.It Dv MAGIC_MIME_ENCODING 118Return a MIME encoding, instead of a textual description. 119.It Dv MAGIC_MIME 120A shorthand for MAGIC_MIME_TYPE | MAGIC_MIME_ENCODING. 121.It Dv MAGIC_CONTINUE 122Return all matches, not just the first. 123.It Dv MAGIC_CHECK 124Check the magic database for consistency and print warnings to stderr. 125.It Dv MAGIC_PRESERVE_ATIME 126On systems that support 127.Xr utime 3 128or 129.Xr utimes 2 , 130attempt to preserve the access time of files analysed. 131.It Dv MAGIC_RAW 132Don't translate unprintable characters to a \eooo octal representation. 133.It Dv MAGIC_ERROR 134Treat operating system errors while trying to open files and follow symlinks 135as real errors, instead of printing them in the magic buffer. 136.It Dv MAGIC_APPLE 137Return the Apple creator and type. 138.It Dv MAGIC_EXTENSION 139Return a slash-separated list of extensions for this file type. 140.It Dv MAGIC_COMPRESS_TRANSP 141Don't report on compression, only report about the uncompressed data. 142.It Dv MAGIC_NO_CHECK_APPTYPE 143Don't check for 144.Dv EMX 145application type (only on EMX). 146.It Dv MAGIC_NO_CHECK_CDF 147Don't get extra information on MS Composite Document Files. 148.It Dv MAGIC_NO_CHECK_COMPRESS 149Don't look inside compressed files. 150.It Dv MAGIC_NO_CHECK_ELF 151Don't print ELF details. 152.It Dv MAGIC_NO_CHECK_ENCODING 153Don't check text encodings. 154.It Dv MAGIC_NO_CHECK_SOFT 155Don't consult magic files. 156.It Dv MAGIC_NO_CHECK_TAR 157Don't examine tar files. 158.It Dv MAGIC_NO_CHECK_TEXT 159Don't check for various types of text files. 160.It Dv MAGIC_NO_CHECK_TOKENS 161Don't look for known tokens inside ascii files. 162.It Dv MAGIC_NO_CHECK_JSON 163Don't example JSON files. 164.El 165.Pp 166The 167.Fn magic_close 168function closes the 169.Xr magic __FSECTION__ 170database and deallocates any resources used. 171.Pp 172The 173.Fn magic_error 174function returns a textual explanation of the last error, or 175.Dv NULL 176if there was no error. 177.Pp 178The 179.Fn magic_errno 180function returns the last operating system error number 181.Pq Xr errno 2 182that was encountered by a system call. 183.Pp 184The 185.Fn magic_file 186function returns a textual description of the contents of the 187.Ar filename 188argument, or 189.Dv NULL 190if an error occurred. 191If the 192.Ar filename 193is 194.Dv NULL , 195then stdin is used. 196.Pp 197The 198.Fn magic_descriptor 199function returns a textual description of the contents of the 200.Ar fd 201argument, or 202.Dv NULL 203if an error occurred. 204.Pp 205The 206.Fn magic_buffer 207function returns a textual description of the contents of the 208.Ar buffer 209argument with 210.Ar length 211bytes size. 212.Pp 213The 214.Fn magic_getflags 215functions returns a value representing current 216.Ar flags 217set. 218.Pp 219The 220.Fn magic_setflags 221function sets the 222.Ar flags 223described above. 224Note that using both MIME flags together can also 225return extra information on the charset. 226.Pp 227The 228.Fn magic_check 229function can be used to check the validity of entries in the colon 230separated database files passed in as 231.Ar filename , 232or 233.Dv NULL 234for the default database. 235It returns 0 on success and \-1 on failure. 236.Pp 237The 238.Fn magic_compile 239function can be used to compile the colon 240separated list of database files passed in as 241.Ar filename , 242or 243.Dv NULL 244for the default database. 245It returns 0 on success and \-1 on failure. 246The compiled files created are named from the 247.Xr basename 1 248of each file argument with 249.Dq .mgc 250appended to it. 251.Pp 252The 253.Fn magic_list 254function dumps all magic entries in a human readable format, 255dumping first the entries that are matched against binary files and then the 256ones that match text files. 257It takes and optional 258.Fa filename 259argument which is a colon separated list of database files, or 260.Dv NULL 261for the default database. 262.Pp 263The 264.Fn magic_load 265function must be used to load the colon 266separated list of database files passed in as 267.Ar filename , 268or 269.Dv NULL 270for the default database file before any magic queries can performed. 271.Pp 272The default database file is named by the MAGIC environment variable. 273If that variable is not set, the default database file name is __MAGIC__. 274.Fn magic_load 275adds 276.Dq .mgc 277to the database filename as appropriate. 278.Pp 279The 280.Fn magic_load_buffers 281function takes an array of size 282.Fa nbuffers 283of 284.Fa buffers 285with a respective size for each in the array of 286.Fa sizes 287loaded with the contents of the magic databases from the filesystem. 288This function can be used in environment where the magic library does 289not have direct access to the filesystem, but can access the magic 290database via shared memory or other IPC means. 291.Pp 292The 293.Fn magic_getparam 294and 295.Fn magic_setparam 296allow getting and setting various limits related to the magic 297library. 298.Bl -column "MAGIC_PARAM_ELF_PHNUM_MAX" "size_t" "Default" -offset indent 299.It Sy "Parameter" Ta Sy "Type" Ta Sy "Default" 300.It Li MAGIC_PARAM_INDIR_MAX Ta size_t Ta 15 301.It Li MAGIC_PARAM_NAME_MAX Ta size_t Ta 30 302.It Li MAGIC_PARAM_ELF_NOTES_MAX Ta size_t Ta 256 303.It Li MAGIC_PARAM_ELF_PHNUM_MAX Ta size_t Ta 128 304.It Li MAGIC_PARAM_ELF_SHNUM_MAX Ta size_t Ta 32768 305.It Li MAGIC_PARAM_REGEX_MAX Ta size_t Ta 8192 306.It Li MAGIC_PARAM_BYTES_MAX Ta size_t Ta 1048576 307.El 308.Pp 309The 310.Dv MAGIC_PARAM_INDIR_RECURSION 311parameter controls how many levels of recursion will be followed for 312indirect magic entries. 313.Pp 314The 315.Dv MAGIC_PARAM_NAME_RECURSION 316parameter controls how many levels of recursion will be followed for 317for name/use calls. 318.Pp 319The 320.Dv MAGIC_PARAM_NAME_MAX 321parameter controls the maximum number of calls for name/use. 322.Pp 323The 324.Dv MAGIC_PARAM_NOTES_MAX 325parameter controls how many ELF notes will be processed. 326.Pp 327The 328.Dv MAGIC_PARAM_PHNUM_MAX 329parameter controls how many ELF program sections will be processed. 330.Pp 331The 332.Dv MAGIC_PARAM_SHNUM_MAX 333parameter controls how many ELF sections will be processed. 334.Pp 335The 336.Fn magic_version 337command returns the version number of this library which is compiled into 338the shared library using the constant 339.Dv MAGIC_VERSION 340from 341.In magic.h . 342This can be used by client programs to verify that the version they compile 343against is the same as the version that they run against. 344.Sh RETURN VALUES 345The function 346.Fn magic_open 347returns a magic cookie on success and 348.Dv NULL 349on failure setting errno to an appropriate value. 350It will set errno to 351.Er EINVAL 352if an unsupported value for flags was given. 353The 354.Fn magic_list , 355.Fn magic_load , 356.Fn magic_compile , 357and 358.Fn magic_check 359functions return 0 on success and \-1 on failure. 360The 361.Fn magic_buffer , 362.Fn magic_getpath , 363and 364.Fn magic_file , 365functions return a string on success and 366.Dv NULL 367on failure. 368The 369.Fn magic_error 370function returns a textual description of the errors of the above 371functions, or 372.Dv NULL 373if there was no error. 374The 375.Fn magic_version 376always returns the version number of the library. 377Finally, 378.Fn magic_setflags 379returns \-1 on systems that don't support 380.Xr utime 3 , 381or 382.Xr utimes 2 383when 384.Dv MAGIC_PRESERVE_ATIME 385is set. 386.Sh FILES 387.Bl -tag -width __MAGIC__.mgc -compact 388.It Pa __MAGIC__ 389The non-compiled default magic database. 390.It Pa __MAGIC__.mgc 391The compiled default magic database. 392.El 393.Sh SEE ALSO 394.Xr file __CSECTION__ , 395.Xr magic __FSECTION__ 396.Sh BUGS 397The results from 398.Fn magic_buffer 399and 400.Fn magic_file 401where the buffer and the file contain the same data 402can produce different results, because in the 403.Fn magic_file 404case, the program can 405.Xr lseek 2 406and 407.Xr stat 2 408the file descriptor. 409.Sh AUTHORS 410.An M\(oans Rullg\(oard 411Initial libmagic implementation, and configuration. 412.An Christos Zoulas 413API cleanup, error code and allocation handling. 414