LIBMAGIC(3)

LIBMAGIC(3) | NetBSD Library Functions Manual | LIBMAGIC(3)

# NAME

magic_open, magic_close, magic_error, magic_descriptor, magic_buffer, magic_setflags, magic_check, magic_compile, magic_load — 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_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_load(magic_t cookie, const char *filename);

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

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_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 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_load() function must be used to load the 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.

# 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_load(), magic_compile(), and magic_check() functions return 0 on success and -1 on failure. The magic_file(), and magic_buffer() 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. 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)

# AUTHORS

Måns Rullgård Initial libmagic implementation, and configuration. Christos Zoulas API cleanup, error code and allocation handling.

January 14, 2011 | NetBSD 5.99