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