man > LIBMAGIC(3)

LIBMAGIC(3)                            Library Functions Manual                          LIBMAGIC(3)

NAME
       magic_open,    magic_close,   magic_error,   magic_errno,   magic_descriptor,   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 argu‐
       ment, 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 argu‐
       ment, or NULL if an error occurred.

       The magic_buffer() function returns a textual description of the contents of the buffer argu‐
       ment 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  sepa‐
       rated  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  argu‐
       ment 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 respec‐
       tive 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  fol‐
       lowed for indirect magic entries.

       The  MAGIC_PARAM_NAME_RECURSION  parameter controls how many levels of recursion will be fol‐
       lowed 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(),  func‐
       tions  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
       Måns Rullgård Initial libmagic implementation, and configuration.
       Christos Zoulas API cleanup, error code and allocation handling.

Debian                                      June 16, 2023                                LIBMAGIC(3)