1.\" $File: libmagic.man,v 1.49 2023/07/20 14:32:07 christos Exp $ 2.\" 3.\" Copyright (c) Christos Zoulas 2003, 2018, 2022 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 16, 2023 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.Ft const char * 88.Fn magic_getpath "const char *magicfile" "int action" 89.Sh DESCRIPTION 90These functions 91operate on the magic database file 92which is described 93in 94.Xr magic __FSECTION__ . 95.Pp 96The function 97.Fn magic_open 98creates a magic cookie pointer and returns it. 99It returns 100.Dv NULL 101if there was an error allocating the magic cookie. 102The 103.Ar flags 104argument specifies how the other magic functions should behave: 105.Bl -tag -width MAGIC_COMPRESS 106.It Dv MAGIC_NONE 107No special handling. 108.It Dv MAGIC_DEBUG 109Print debugging messages to stderr. 110.It Dv MAGIC_SYMLINK 111If the file queried is a symlink, follow it. 112.It Dv MAGIC_COMPRESS 113If the file is compressed, unpack it and look at the contents. 114.It Dv MAGIC_DEVICES 115If the file is a block or character special device, then open the device 116and try to look in its contents. 117.It Dv MAGIC_MIME_TYPE 118Return a MIME type string, instead of a textual description. 119.It Dv MAGIC_MIME_ENCODING 120Return a MIME encoding, instead of a textual description. 121.It Dv MAGIC_MIME 122A shorthand for MAGIC_MIME_TYPE | MAGIC_MIME_ENCODING. 123.It Dv MAGIC_CONTINUE 124Return all matches, not just the first. 125.It Dv MAGIC_CHECK 126Check the magic database for consistency and print warnings to stderr. 127.It Dv MAGIC_PRESERVE_ATIME 128On systems that support 129.Xr utime 3 130or 131.Xr utimes 2 , 132attempt to preserve the access time of files analysed. 133.It Dv MAGIC_RAW 134Don't translate unprintable characters to a \eooo octal representation. 135.It Dv MAGIC_ERROR 136Treat operating system errors while trying to open files and follow symlinks 137as real errors, instead of printing them in the magic buffer. 138.It Dv MAGIC_APPLE 139Return the Apple creator and type. 140.It Dv MAGIC_EXTENSION 141Return a slash-separated list of extensions for this file type. 142.It Dv MAGIC_COMPRESS_TRANSP 143Don't report on compression, only report about the uncompressed data. 144.It Dv MAGIC_NO_CHECK_APPTYPE 145Don't check for 146.Dv EMX 147application type (only on EMX). 148.It Dv MAGIC_NO_COMPRESS_FORK 149Don't allow decompressors that use fork. 150.It Dv MAGIC_NO_CHECK_CDF 151Don't get extra information on MS Composite Document Files. 152.It Dv MAGIC_NO_CHECK_COMPRESS 153Don't look inside compressed files. 154.It Dv MAGIC_NO_CHECK_ELF 155Don't print ELF details. 156.It Dv MAGIC_NO_CHECK_ENCODING 157Don't check text encodings. 158.It Dv MAGIC_NO_CHECK_SOFT 159Don't consult magic files. 160.It Dv MAGIC_NO_CHECK_TAR 161Don't examine tar files. 162.It Dv MAGIC_NO_CHECK_TEXT 163Don't check for various types of text files. 164.It Dv MAGIC_NO_CHECK_TOKENS 165Don't look for known tokens inside ascii files. 166.It Dv MAGIC_NO_CHECK_JSON 167Don't examine JSON files. 168.It Dv MAGIC_NO_CHECK_CSV 169Don't examine CSV files. 170.It Dv MAGIC_NO_CHECK_SIMH 171Don't examine SIMH tape files. 172.El 173.Pp 174The 175.Fn magic_close 176function closes the 177.Xr magic __FSECTION__ 178database and deallocates any resources used. 179.Pp 180The 181.Fn magic_error 182function returns a textual explanation of the last error, or 183.Dv NULL 184if there was no error. 185.Pp 186The 187.Fn magic_errno 188function returns the last operating system error number 189.Pq Xr errno 2 190that was encountered by a system call. 191.Pp 192The 193.Fn magic_file 194function returns a textual description of the contents of the 195.Ar filename 196argument, or 197.Dv NULL 198if an error occurred. 199If the 200.Ar filename 201is 202.Dv NULL , 203then stdin is used. 204.Pp 205The 206.Fn magic_descriptor 207function returns a textual description of the contents of the 208.Ar fd 209argument, or 210.Dv NULL 211if an error occurred. 212.Pp 213The 214.Fn magic_buffer 215function returns a textual description of the contents of the 216.Ar buffer 217argument with 218.Ar length 219bytes size. 220.Pp 221The 222.Fn magic_getflags 223functions returns a value representing current 224.Ar flags 225set. 226.Pp 227The 228.Fn magic_setflags 229function sets the 230.Ar flags 231described above. 232Note that using both MIME flags together can also 233return extra information on the charset. 234.Pp 235The 236.Fn magic_check 237function can be used to check the validity of entries in the colon 238separated database files passed in as 239.Ar filename , 240or 241.Dv NULL 242for the default database. 243It returns 0 on success and \-1 on failure. 244.Pp 245The 246.Fn magic_compile 247function can be used to compile the colon 248separated list of database files passed in as 249.Ar filename , 250or 251.Dv NULL 252for the default database. 253It returns 0 on success and \-1 on failure. 254The compiled files created are named from the 255.Xr basename 1 256of each file argument with 257.Dq .mgc 258appended to it. 259.Pp 260The 261.Fn magic_list 262function dumps all magic entries in a human readable format, 263dumping first the entries that are matched against binary files and then the 264ones that match text files. 265It takes and optional 266.Fa filename 267argument which is a colon separated list of database files, or 268.Dv NULL 269for the default database. 270.Pp 271The 272.Fn magic_load 273function must be used to load the colon 274separated list of database files passed in as 275.Ar filename , 276or 277.Dv NULL 278for the default database file before any magic queries can performed. 279.Pp 280The default database file is named by the MAGIC environment variable. 281If that variable is not set, the default database file name is __MAGIC__. 282.Fn magic_load 283adds 284.Dq .mgc 285to the database filename as appropriate. 286.Pp 287The 288.Fn magic_load_buffers 289function takes an array of size 290.Fa nbuffers 291of 292.Fa buffers 293with a respective size for each in the array of 294.Fa sizes 295loaded with the contents of the magic databases from the filesystem. 296This function can be used in environment where the magic library does 297not have direct access to the filesystem, but can access the magic 298database via shared memory or other IPC means. 299.Pp 300The 301.Fn magic_getparam 302and 303.Fn magic_setparam 304allow getting and setting various limits related to the magic 305library. 306.Bl -column "MAGIC_PARAM_ELF_PHNUM_MAX" "size_t" "Default" -offset indent 307.It Sy "Parameter" Ta Sy "Type" Ta Sy "Default" 308.It Li MAGIC_PARAM_INDIR_MAX Ta size_t Ta 15 309.It Li MAGIC_PARAM_NAME_MAX Ta size_t Ta 30 310.It Li MAGIC_PARAM_ELF_NOTES_MAX Ta size_t Ta 256 311.It Li MAGIC_PARAM_ELF_PHNUM_MAX Ta size_t Ta 128 312.It Li MAGIC_PARAM_ELF_SHNUM_MAX Ta size_t Ta 32768 313.It Li MAGIC_PARAM_REGEX_MAX Ta size_t Ta 8192 314.It Li MAGIC_PARAM_BYTES_MAX Ta size_t Ta 1048576 315.El 316.Pp 317The 318.Dv MAGIC_PARAM_INDIR_RECURSION 319parameter controls how many levels of recursion will be followed for 320indirect magic entries. 321.Pp 322The 323.Dv MAGIC_PARAM_NAME_RECURSION 324parameter controls how many levels of recursion will be followed for 325for name/use calls. 326.Pp 327The 328.Dv MAGIC_PARAM_NAME_MAX 329parameter controls the maximum number of calls for name/use. 330.Pp 331The 332.Dv MAGIC_PARAM_NOTES_MAX 333parameter controls how many ELF notes will be processed. 334.Pp 335The 336.Dv MAGIC_PARAM_PHNUM_MAX 337parameter controls how many ELF program sections will be processed. 338.Pp 339The 340.Dv MAGIC_PARAM_SHNUM_MAX 341parameter controls how many ELF sections will be processed. 342.Pp 343The 344.Fn magic_version 345command returns the version number of this library which is compiled into 346the shared library using the constant 347.Dv MAGIC_VERSION 348from 349.In magic.h . 350This can be used by client programs to verify that the version they compile 351against is the same as the version that they run against. 352.Pp 353The 354.Fn magic_getpath 355command returns the colon separated list of magic database locations. 356If the 357.Fa filename 358is non-NULL, then it is returned. 359Otherwise, if the 360.Dv MAGIC 361environment variable is defined, then it is returned. 362Otherwise, if 363.Fa action 364is 0 (meaning "file load"), then any user-specific magic database file is included. 365Otherwise, only the system default magic database path is included. 366.Sh RETURN VALUES 367The function 368.Fn magic_open 369returns a magic cookie on success and 370.Dv NULL 371on failure setting errno to an appropriate value. 372It will set errno to 373.Er EINVAL 374if an unsupported value for flags was given. 375The 376.Fn magic_list , 377.Fn magic_load , 378.Fn magic_compile , 379and 380.Fn magic_check 381functions return 0 on success and \-1 on failure. 382The 383.Fn magic_buffer , 384.Fn magic_getpath , 385and 386.Fn magic_file , 387functions return a string on success and 388.Dv NULL 389on failure. 390The 391.Fn magic_error 392function returns a textual description of the errors of the above 393functions, or 394.Dv NULL 395if there was no error. 396The 397.Fn magic_version 398always returns the version number of the library. 399Finally, 400.Fn magic_setflags 401returns \-1 on systems that don't support 402.Xr utime 3 , 403or 404.Xr utimes 2 405when 406.Dv MAGIC_PRESERVE_ATIME 407is set. 408.Sh FILES 409.Bl -tag -width __MAGIC__.mgc -compact 410.It Pa __MAGIC__ 411The non-compiled default magic database. 412.It Pa __MAGIC__.mgc 413The compiled default magic database. 414.El 415.Sh SEE ALSO 416.Xr file __CSECTION__ , 417.Xr magic __FSECTION__ 418.Sh BUGS 419The results from 420.Fn magic_buffer 421and 422.Fn magic_file 423where the buffer and the file contain the same data 424can produce different results, because in the 425.Fn magic_file 426case, the program can 427.Xr lseek 2 428and 429.Xr stat 2 430the file descriptor. 431.Sh AUTHORS 432.An M\(oans Rullg\(oard 433Initial libmagic implementation, and configuration. 434.An Christos Zoulas 435API cleanup, error code and allocation handling. 436