1.\" $NetBSD: libmagic.3,v 1.18 2018/10/19 00:11:48 christos Exp $ 2.\" 3.\" $File: libmagic.man,v 1.44 2018/09/09 20:33:28 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 August 18, 2018 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 example JSON files. 167.El 168.Pp 169The 170.Fn magic_close 171function closes the 172.Xr magic 5 173database and deallocates any resources used. 174.Pp 175The 176.Fn magic_error 177function returns a textual explanation of the last error, or 178.Dv NULL 179if there was no error. 180.Pp 181The 182.Fn magic_errno 183function returns the last operating system error number 184.Pq Xr errno 2 185that was encountered by a system call. 186.Pp 187The 188.Fn magic_file 189function returns a textual description of the contents of the 190.Ar filename 191argument, or 192.Dv NULL 193if an error occurred. 194If the 195.Ar filename 196is 197.Dv NULL , 198then stdin is used. 199.Pp 200The 201.Fn magic_descriptor 202function returns a textual description of the contents of the 203.Ar fd 204argument, or 205.Dv NULL 206if an error occurred. 207.Pp 208The 209.Fn magic_buffer 210function returns a textual description of the contents of the 211.Ar buffer 212argument with 213.Ar length 214bytes size. 215.Pp 216The 217.Fn magic_getflags 218functions returns a value representing current 219.Ar flags 220set. 221.Pp 222The 223.Fn magic_setflags 224function sets the 225.Ar flags 226described above. 227Note that using both MIME flags together can also 228return extra information on the charset. 229.Pp 230The 231.Fn magic_check 232function can be used to check the validity of entries in the colon 233separated database files passed in as 234.Ar filename , 235or 236.Dv NULL 237for the default database. 238It returns 0 on success and \-1 on failure. 239.Pp 240The 241.Fn magic_compile 242function can be used to compile the colon 243separated list of database files passed in as 244.Ar filename , 245or 246.Dv NULL 247for the default database. 248It returns 0 on success and \-1 on failure. 249The compiled files created are named from the 250.Xr basename 1 251of each file argument with 252.Dq .mgc 253appended to it. 254.Pp 255The 256.Fn magic_list 257function dumps all magic entries in a human readable format, 258dumping first the entries that are matched against binary files and then the 259ones that match text files. 260It takes and optional 261.Fa filename 262argument which is a colon separated list of database files, or 263.Dv NULL 264for the default database. 265.Pp 266The 267.Fn magic_load 268function must be used to load the colon 269separated list of database files passed in as 270.Ar filename , 271or 272.Dv NULL 273for the default database file before any magic queries can performed. 274.Pp 275The default database file is named by the MAGIC environment variable. 276If that variable is not set, the default database file name is 277.Pa /usr/share/misc/magic . 278.Fn magic_load 279adds 280.Dq .mgc 281to the database filename as appropriate. 282.Pp 283The 284.Fn magic_load_buffers 285function takes an array of size 286.Fa nbuffers 287of 288.Fa buffers 289with a respective size for each in the array of 290.Fa sizes 291loaded with the contents of the magic databases from the filesystem. 292This function can be used in environment where the magic library does 293not have direct access to the filesystem, but can access the magic 294database via shared memory or other IPC means. 295.Pp 296The 297.Fn magic_getparam 298and 299.Fn magic_setparam 300allow getting and setting various limits related to the magic 301library. 302.Bl -column "MAGIC_PARAM_ELF_PHNUM_MAX" "size_t" "Default" -offset indent 303.It Sy "Parameter" Ta Sy "Type" Ta Sy "Default" 304.It Li MAGIC_PARAM_INDIR_MAX Ta size_t Ta 15 305.It Li MAGIC_PARAM_NAME_MAX Ta size_t Ta 30 306.It Li MAGIC_PARAM_ELF_NOTES_MAX Ta size_t Ta 256 307.It Li MAGIC_PARAM_ELF_PHNUM_MAX Ta size_t Ta 128 308.It Li MAGIC_PARAM_ELF_SHNUM_MAX Ta size_t Ta 32768 309.It Li MAGIC_PARAM_REGEX_MAX Ta size_t Ta 8192 310.It Li MAGIC_PARAM_BYTES_MAX Ta size_t Ta 1048576 311.El 312.Pp 313The 314.Dv MAGIC_PARAM_INDIR_RECURSION 315parameter controls how many levels of recursion will be followed for 316indirect magic entries. 317.Pp 318The 319.Dv MAGIC_PARAM_NAME_RECURSION 320parameter controls how many levels of recursion will be followed for 321for name/use calls. 322.Pp 323The 324.Dv MAGIC_PARAM_NAME_MAX 325parameter controls the maximum number of calls for name/use. 326.Pp 327The 328.Dv MAGIC_PARAM_NOTES_MAX 329parameter controls how many ELF notes will be processed. 330.Pp 331The 332.Dv MAGIC_PARAM_PHNUM_MAX 333parameter controls how many ELF program sections will be processed. 334.Pp 335The 336.Dv MAGIC_PARAM_SHNUM_MAX 337parameter controls how many ELF sections will be processed. 338.Pp 339The 340.Fn magic_version 341command returns the version number of this library which is compiled into 342the shared library using the constant 343.Dv MAGIC_VERSION 344from 345.In magic.h . 346This can be used by client programs to verify that the version they compile 347against is the same as the version that they run against. 348.Sh RETURN VALUES 349The function 350.Fn magic_open 351returns a magic cookie on success and 352.Dv NULL 353on failure setting errno to an appropriate value. 354It will set errno to 355.Er EINVAL 356if an unsupported value for flags was given. 357The 358.Fn magic_list , 359.Fn magic_load , 360.Fn magic_compile , 361and 362.Fn magic_check 363functions return 0 on success and \-1 on failure. 364The 365.Fn magic_buffer , 366.Fn magic_getpath , 367and 368.Fn magic_file , 369functions return a string on success and 370.Dv NULL 371on failure. 372The 373.Fn magic_error 374function returns a textual description of the errors of the above 375functions, or 376.Dv NULL 377if there was no error. 378The 379.Fn magic_version 380always returns the version number of the library. 381Finally, 382.Fn magic_setflags 383returns \-1 on systems that don't support 384.Xr utime 3 , 385or 386.Xr utimes 2 387when 388.Dv MAGIC_PRESERVE_ATIME 389is set. 390.Sh FILES 391.Bl -tag -width /usr/share/misc/magic.mgc -compact 392.It Pa /usr/share/misc/magic 393The non-compiled default magic database. 394.It Pa /usr/share/misc/magic.mgc 395The compiled default magic database. 396.El 397.Sh SEE ALSO 398.Xr file 1 , 399.Xr magic 5 400.Sh BUGS 401The results from 402.Fn magic_buffer 403and 404.Fn magic_file 405where the buffer and the file contain the same data 406can produce different results, because in the 407.Fn magic_file 408case, the program can 409.Xr lseek 2 410and 411.Xr stat 2 412the file descriptor. 413.Sh AUTHORS 414.An M\(oans Rullg\(oard 415Initial libmagic implementation, and configuration. 416.An Christos Zoulas 417API cleanup, error code and allocation handling. 418