Updated: 2022/Sep/29

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LIBMAGIC(3)                Library Functions Manual                LIBMAGIC(3)

NAME
     magic_open, magic_close, magic_error, magic_errno, magic_descriptor,
     magic_file, magic_buffer, magic_getflags, magic_setflags, magic_check,
     magic_compile, magic_list, magic_load, magic_load_buffers,
     magic_setparam, magic_getparam, magic_version - Magic number recognition
     library

LIBRARY
     Magic Number Recognition Library (libmagic, -lmagic)

SYNOPSIS
     #include <magic.h>

     magic_t
     magic_open(int flags);

     void
     magic_close(magic_t cookie);

     const char *
     magic_error(magic_t cookie);

     int
     magic_errno(magic_t cookie);

     const char *
     magic_descriptor(magic_t cookie, int fd);

     const char *
     magic_file(magic_t cookie, const char *filename);

     const char *
     magic_buffer(magic_t cookie, const void *buffer, size_t length);

     int
     magic_getflags(magic_t cookie);

     int
     magic_setflags(magic_t cookie, int flags);

     int
     magic_check(magic_t cookie, const char *filename);

     int
     magic_compile(magic_t cookie, const char *filename);

     int
     magic_list(magic_t cookie, const char *filename);

     int
     magic_load(magic_t cookie, const char *filename);

     int
     magic_load_buffers(magic_t cookie, void **buffers, size_t *sizes,
         size_t nbuffers);

     int
     magic_getparam(magic_t cookie, int param, void *value);

     int
     magic_setparam(magic_t cookie, int param, const void *value);

     int
     magic_version(void);

     const char *
     magic_getpath(const char *magicfile, int action);

DESCRIPTION
     These functions operate on the magic database file which is described in
     magic(5).

     The function magic_open() creates a magic cookie pointer and returns it.
     It returns NULL if there was an error allocating the magic cookie.  The
     flags argument specifies how the other magic functions should behave:

     MAGIC_NONE      No special handling.

     MAGIC_DEBUG     Print debugging messages to stderr.

     MAGIC_SYMLINK   If the file queried is a symlink, follow it.

     MAGIC_COMPRESS  If the file is compressed, unpack it and look at the
                     contents.

     MAGIC_DEVICES   If the file is a block or character special device, then
                     open the device and try to look in its contents.

     MAGIC_MIME_TYPE
                     Return a MIME type string, instead of a textual
                     description.

     MAGIC_MIME_ENCODING
                     Return a MIME encoding, instead of a textual description.

     MAGIC_MIME      A shorthand for MAGIC_MIME_TYPE | MAGIC_MIME_ENCODING.

     MAGIC_CONTINUE  Return all matches, not just the first.

     MAGIC_CHECK     Check the magic database for consistency and print
                     warnings to stderr.

     MAGIC_PRESERVE_ATIME
                     On systems that support utime(3) or utimes(2), attempt to
                     preserve the access time of files analysed.

     MAGIC_RAW       Don't translate unprintable characters to a \ooo octal
                     representation.

     MAGIC_ERROR     Treat operating system errors while trying to open files
                     and follow symlinks as real errors, instead of printing
                     them in the magic buffer.

     MAGIC_APPLE     Return the Apple creator and type.

     MAGIC_EXTENSION
                     Return a slash-separated list of extensions for this file
                     type.

     MAGIC_COMPRESS_TRANSP
                     Don't report on compression, only report about the
                     uncompressed data.

     MAGIC_NO_CHECK_APPTYPE
                     Don't check for EMX application type (only on EMX).

     MAGIC_NO_COMPRESS_FORK
                     Don't allow decompressors that use fork.

     MAGIC_NO_CHECK_CDF
                     Don't get extra information on MS Composite Document
                     Files.

     MAGIC_NO_CHECK_COMPRESS
                     Don't look inside compressed files.

     MAGIC_NO_CHECK_ELF
                     Don't print ELF details.

     MAGIC_NO_CHECK_ENCODING
                     Don't check text encodings.

     MAGIC_NO_CHECK_SOFT
                     Don't consult magic files.

     MAGIC_NO_CHECK_TAR
                     Don't examine tar files.

     MAGIC_NO_CHECK_TEXT
                     Don't check for various types of text files.

     MAGIC_NO_CHECK_TOKENS
                     Don't look for known tokens inside ascii files.

     MAGIC_NO_CHECK_JSON
                     Don't examine JSON files.

     MAGIC_NO_CHECK_CSV
                     Don't examine CSV files.

     MAGIC_NO_CHECK_SIMH
                     Don't examine SIMH tape files.

     The magic_close() function closes the magic(5) database and deallocates
     any resources used.

     The magic_error() function returns a textual explanation of the last
     error, or NULL if there was no error.

     The magic_errno() function returns the last operating system error number
     (errno(2)) that was encountered by a system call.

     The magic_file() function returns a textual description of the contents
     of the filename argument, or NULL if an error occurred.  If the filename
     is NULL, then stdin is used.

     The magic_descriptor() function returns a textual description of the
     contents of the fd argument, or NULL if an error occurred.

     The magic_buffer() function returns a textual description of the contents
     of the buffer argument with length bytes size.

     The magic_getflags() functions returns a value representing current flags
     set.

     The magic_setflags() function sets the flags described above.  Note that
     using both MIME flags together can also return extra information on the
     charset.

     The magic_check() function can be used to check the validity of entries
     in the colon separated database files passed in as filename, or NULL for
     the default database.  It returns 0 on success and -1 on failure.

     The magic_compile() function can be used to compile the colon separated
     list of database files passed in as filename, or NULL for the default
     database.  It returns 0 on success and -1 on failure.  The compiled files
     created are named from the basename(1) of each file argument with ".mgc"
     appended to it.

     The magic_list() function dumps all magic entries in a human readable
     format, dumping first the entries that are matched against binary files
     and then the ones that match text files.  It takes and optional filename
     argument which is a colon separated list of database files, or NULL for
     the default database.

     The magic_load() function must be used to load the colon separated list
     of database files passed in as filename, or NULL for the default database
     file before any magic queries can performed.

     The default database file is named by the MAGIC environment variable.  If
     that variable is not set, the default database file name is
     /usr/share/misc/magic.  magic_load() adds ".mgc" to the database filename
     as appropriate.

     The magic_load_buffers() function takes an array of size nbuffers of
     buffers with a respective size for each in the array of sizes loaded with
     the contents of the magic databases from the filesystem.  This function
     can be used in environment where the magic library does not have direct
     access to the filesystem, but can access the magic database via shared
     memory or other IPC means.

     The magic_getparam() and magic_setparam() allow getting and setting
     various limits related to the magic library.

           Parameter                    Type      Default
           MAGIC_PARAM_INDIR_MAX        size_t    15
           MAGIC_PARAM_NAME_MAX         size_t    30
           MAGIC_PARAM_ELF_NOTES_MAX    size_t    256
           MAGIC_PARAM_ELF_PHNUM_MAX    size_t    128
           MAGIC_PARAM_ELF_SHNUM_MAX    size_t    32768
           MAGIC_PARAM_REGEX_MAX        size_t    8192
           MAGIC_PARAM_BYTES_MAX        size_t    1048576

     The MAGIC_PARAM_INDIR_RECURSION parameter controls how many levels of
     recursion will be followed for indirect magic entries.

     The MAGIC_PARAM_NAME_RECURSION parameter controls how many levels of
     recursion will be followed for for name/use calls.

     The MAGIC_PARAM_NAME_MAX parameter controls the maximum number of calls
     for name/use.

     The MAGIC_PARAM_NOTES_MAX parameter controls how many ELF notes will be
     processed.

     The MAGIC_PARAM_PHNUM_MAX parameter controls how many ELF program
     sections will be processed.

     The MAGIC_PARAM_SHNUM_MAX parameter controls how many ELF sections will
     be processed.

     The magic_version() command returns the version number of this library
     which is compiled into the shared library using the constant
     MAGIC_VERSION from <magic.h>.  This can be used by client programs to
     verify that the version they compile against is the same as the version
     that they run against.

     The magic_getpath() command returns the colon separated list of magic
     database locations.  If the filename is non-NULL, then it is returned.
     Otherwise, if the MAGIC environment variable is defined, then it is
     returned.  Otherwise, if action is 0 (meaning "file load"), then any
     user-specific magic database file is included.  Otherwise, only the
     system default magic database path is included.

RETURN VALUES
     The function magic_open() returns a magic cookie on success and NULL on
     failure setting errno to an appropriate value.  It will set errno to
     EINVAL if an unsupported value for flags was given.  The magic_list(),
     magic_load(), magic_compile(), and magic_check() functions return 0 on
     success and -1 on failure.  The magic_buffer(), magic_getpath(), and
     magic_file(), functions return a string on success and NULL on failure.
     The magic_error() function returns a textual description of the errors of
     the above functions, or NULL if there was no error.  The magic_version()
     always returns the version number of the library.  Finally,
     magic_setflags() returns -1 on systems that don't support utime(3), or
     utimes(2) when MAGIC_PRESERVE_ATIME is set.

FILES
     /usr/share/misc/magic      The non-compiled default magic database.
     /usr/share/misc/magic.mgc  The compiled default magic database.

SEE ALSO
     file(1), magic(5)

BUGS
     The results from magic_buffer() and magic_file() where the buffer and the
     file contain the same data can produce different results, because in the
     magic_file() case, the program can lseek(2) and stat(2) the file
     descriptor.

AUTHORS
     Moans Rullgoard Initial libmagic implementation, and configuration.
     Christos Zoulas API cleanup, error code and allocation handling.

NetBSD 10.99                     June 16, 2023                    NetBSD 10.99