1.\" $NetBSD: libmagic.3,v 1.19 2019/12/17 02:31:05 christos Exp $ 2.\" 3.\" $File: libmagic.man,v 1.45 2019/06/08 22:16:24 christos Exp $ 4.\" 5.\" Copyright (c) Christos Zoulas 2003, 2018. 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 June 8, 2019 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.It Dv MAGIC_NO_CHECK_JSON 166Don't examine JSON files. 167.It Dv MAGIC_NO_CHECK_CSV 168Don't examine CSV files. 169.El 170.Pp 171The 172.Fn magic_close 173function closes the 174.Xr magic 5 175database and deallocates any resources used. 176.Pp 177The 178.Fn magic_error 179function returns a textual explanation of the last error, or 180.Dv NULL 181if there was no error. 182.Pp 183The 184.Fn magic_errno 185function returns the last operating system error number 186.Pq Xr errno 2 187that was encountered by a system call. 188.Pp 189The 190.Fn magic_file 191function returns a textual description of the contents of the 192.Ar filename 193argument, or 194.Dv NULL 195if an error occurred. 196If the 197.Ar filename 198is 199.Dv NULL , 200then stdin is used. 201.Pp 202The 203.Fn magic_descriptor 204function returns a textual description of the contents of the 205.Ar fd 206argument, or 207.Dv NULL 208if an error occurred. 209.Pp 210The 211.Fn magic_buffer 212function returns a textual description of the contents of the 213.Ar buffer 214argument with 215.Ar length 216bytes size. 217.Pp 218The 219.Fn magic_getflags 220functions returns a value representing current 221.Ar flags 222set. 223.Pp 224The 225.Fn magic_setflags 226function sets the 227.Ar flags 228described above. 229Note that using both MIME flags together can also 230return extra information on the charset. 231.Pp 232The 233.Fn magic_check 234function can be used to check the validity of entries in the colon 235separated database files passed in as 236.Ar filename , 237or 238.Dv NULL 239for the default database. 240It returns 0 on success and \-1 on failure. 241.Pp 242The 243.Fn magic_compile 244function can be used to compile the colon 245separated list of database files passed in as 246.Ar filename , 247or 248.Dv NULL 249for the default database. 250It returns 0 on success and \-1 on failure. 251The compiled files created are named from the 252.Xr basename 1 253of each file argument with 254.Dq .mgc 255appended to it. 256.Pp 257The 258.Fn magic_list 259function dumps all magic entries in a human readable format, 260dumping first the entries that are matched against binary files and then the 261ones that match text files. 262It takes and optional 263.Fa filename 264argument which is a colon separated list of database files, or 265.Dv NULL 266for the default database. 267.Pp 268The 269.Fn magic_load 270function must be used to load the colon 271separated list of database files passed in as 272.Ar filename , 273or 274.Dv NULL 275for the default database file before any magic queries can performed. 276.Pp 277The default database file is named by the MAGIC environment variable. 278If that variable is not set, the default database file name is 279.Pa /usr/share/misc/magic . 280.Fn magic_load 281adds 282.Dq .mgc 283to the database filename as appropriate. 284.Pp 285The 286.Fn magic_load_buffers 287function takes an array of size 288.Fa nbuffers 289of 290.Fa buffers 291with a respective size for each in the array of 292.Fa sizes 293loaded with the contents of the magic databases from the filesystem. 294This function can be used in environment where the magic library does 295not have direct access to the filesystem, but can access the magic 296database via shared memory or other IPC means. 297.Pp 298The 299.Fn magic_getparam 300and 301.Fn magic_setparam 302allow getting and setting various limits related to the magic 303library. 304.Bl -column "MAGIC_PARAM_ELF_PHNUM_MAX" "size_t" "Default" -offset indent 305.It Sy "Parameter" Ta Sy "Type" Ta Sy "Default" 306.It Li MAGIC_PARAM_INDIR_MAX Ta size_t Ta 15 307.It Li MAGIC_PARAM_NAME_MAX Ta size_t Ta 30 308.It Li MAGIC_PARAM_ELF_NOTES_MAX Ta size_t Ta 256 309.It Li MAGIC_PARAM_ELF_PHNUM_MAX Ta size_t Ta 128 310.It Li MAGIC_PARAM_ELF_SHNUM_MAX Ta size_t Ta 32768 311.It Li MAGIC_PARAM_REGEX_MAX Ta size_t Ta 8192 312.It Li MAGIC_PARAM_BYTES_MAX Ta size_t Ta 1048576 313.El 314.Pp 315The 316.Dv MAGIC_PARAM_INDIR_RECURSION 317parameter controls how many levels of recursion will be followed for 318indirect magic entries. 319.Pp 320The 321.Dv MAGIC_PARAM_NAME_RECURSION 322parameter controls how many levels of recursion will be followed for 323for name/use calls. 324.Pp 325The 326.Dv MAGIC_PARAM_NAME_MAX 327parameter controls the maximum number of calls for name/use. 328.Pp 329The 330.Dv MAGIC_PARAM_NOTES_MAX 331parameter controls how many ELF notes will be processed. 332.Pp 333The 334.Dv MAGIC_PARAM_PHNUM_MAX 335parameter controls how many ELF program sections will be processed. 336.Pp 337The 338.Dv MAGIC_PARAM_SHNUM_MAX 339parameter controls how many ELF sections will be processed. 340.Pp 341The 342.Fn magic_version 343command returns the version number of this library which is compiled into 344the shared library using the constant 345.Dv MAGIC_VERSION 346from 347.In magic.h . 348This can be used by client programs to verify that the version they compile 349against is the same as the version that they run against. 350.Sh RETURN VALUES 351The function 352.Fn magic_open 353returns a magic cookie on success and 354.Dv NULL 355on failure setting errno to an appropriate value. 356It will set errno to 357.Er EINVAL 358if an unsupported value for flags was given. 359The 360.Fn magic_list , 361.Fn magic_load , 362.Fn magic_compile , 363and 364.Fn magic_check 365functions return 0 on success and \-1 on failure. 366The 367.Fn magic_buffer , 368.Fn magic_getpath , 369and 370.Fn magic_file , 371functions return a string on success and 372.Dv NULL 373on failure. 374The 375.Fn magic_error 376function returns a textual description of the errors of the above 377functions, or 378.Dv NULL 379if there was no error. 380The 381.Fn magic_version 382always returns the version number of the library. 383Finally, 384.Fn magic_setflags 385returns \-1 on systems that don't support 386.Xr utime 3 , 387or 388.Xr utimes 2 389when 390.Dv MAGIC_PRESERVE_ATIME 391is set. 392.Sh FILES 393.Bl -tag -width /usr/share/misc/magic.mgc -compact 394.It Pa /usr/share/misc/magic 395The non-compiled default magic database. 396.It Pa /usr/share/misc/magic.mgc 397The compiled default magic database. 398.El 399.Sh SEE ALSO 400.Xr file 1 , 401.Xr magic 5 402.Sh BUGS 403The results from 404.Fn magic_buffer 405and 406.Fn magic_file 407where the buffer and the file contain the same data 408can produce different results, because in the 409.Fn magic_file 410case, the program can 411.Xr lseek 2 412and 413.Xr stat 2 414the file descriptor. 415.Sh AUTHORS 416.An M\(oans Rullg\(oard 417Initial libmagic implementation, and configuration. 418.An Christos Zoulas 419API cleanup, error code and allocation handling. 420