1.\" $File: libmagic.man,v 1.45 2019/06/08 22:16:24 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 June 8, 2019 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 examine JSON files. 164.It Dv MAGIC_NO_CHECK_CSV 165Don't examine CSV files. 166.El 167.Pp 168The 169.Fn magic_close 170function closes the 171.Xr magic __FSECTION__ 172database and deallocates any resources used. 173.Pp 174The 175.Fn magic_error 176function returns a textual explanation of the last error, or 177.Dv NULL 178if there was no error. 179.Pp 180The 181.Fn magic_errno 182function returns the last operating system error number 183.Pq Xr errno 2 184that was encountered by a system call. 185.Pp 186The 187.Fn magic_file 188function returns a textual description of the contents of the 189.Ar filename 190argument, or 191.Dv NULL 192if an error occurred. 193If the 194.Ar filename 195is 196.Dv NULL , 197then stdin is used. 198.Pp 199The 200.Fn magic_descriptor 201function returns a textual description of the contents of the 202.Ar fd 203argument, or 204.Dv NULL 205if an error occurred. 206.Pp 207The 208.Fn magic_buffer 209function returns a textual description of the contents of the 210.Ar buffer 211argument with 212.Ar length 213bytes size. 214.Pp 215The 216.Fn magic_getflags 217functions returns a value representing current 218.Ar flags 219set. 220.Pp 221The 222.Fn magic_setflags 223function sets the 224.Ar flags 225described above. 226Note that using both MIME flags together can also 227return extra information on the charset. 228.Pp 229The 230.Fn magic_check 231function can be used to check the validity of entries in the colon 232separated database files passed in as 233.Ar filename , 234or 235.Dv NULL 236for the default database. 237It returns 0 on success and \-1 on failure. 238.Pp 239The 240.Fn magic_compile 241function can be used to compile the colon 242separated list of database files passed in as 243.Ar filename , 244or 245.Dv NULL 246for the default database. 247It returns 0 on success and \-1 on failure. 248The compiled files created are named from the 249.Xr basename 1 250of each file argument with 251.Dq .mgc 252appended to it. 253.Pp 254The 255.Fn magic_list 256function dumps all magic entries in a human readable format, 257dumping first the entries that are matched against binary files and then the 258ones that match text files. 259It takes and optional 260.Fa filename 261argument which is a colon separated list of database files, or 262.Dv NULL 263for the default database. 264.Pp 265The 266.Fn magic_load 267function must be used to load the colon 268separated list of database files passed in as 269.Ar filename , 270or 271.Dv NULL 272for the default database file before any magic queries can performed. 273.Pp 274The default database file is named by the MAGIC environment variable. 275If that variable is not set, the default database file name is __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 __MAGIC__.mgc -compact 390.It Pa __MAGIC__ 391The non-compiled default magic database. 392.It Pa __MAGIC__.mgc 393The compiled default magic database. 394.El 395.Sh SEE ALSO 396.Xr file __CSECTION__ , 397.Xr magic __FSECTION__ 398.Sh BUGS 399The results from 400.Fn magic_buffer 401and 402.Fn magic_file 403where the buffer and the file contain the same data 404can produce different results, because in the 405.Fn magic_file 406case, the program can 407.Xr lseek 2 408and 409.Xr stat 2 410the file descriptor. 411.Sh AUTHORS 412.An M\(oans Rullg\(oard 413Initial libmagic implementation, and configuration. 414.An Christos Zoulas 415API cleanup, error code and allocation handling. 416