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LIBMAGIC(3) | Library Functions Manual | LIBMAGIC(3) |
NAME¶
magic_open, magic_close, magic_error, magic_errno, magic_descriptor, magic_buffer, magic_setflags, magic_check, magic_compile, magic_list, magic_load, magic_load_buffers, magic_setparam, magic_getparam, magic_version — Magic number recognition libraryLIBRARY¶
Magic Number Recognition Library (libmagic, -lmagic)SYNOPSIS¶
#include <magic.h> magic_tmagic_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_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);
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 returnsNULL
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.
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_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 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 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_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.
RETURN VALUES¶
The function magic_open() returns a magic cookie on success andNULL
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)AUTHORS¶
Måns Rullgård Initial libmagic implementation, and configuration.Christos Zoulas API cleanup, error code and allocation handling.
December 16, 2014 | Debian |