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
Return a mime string, instead of a textual description.
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(2)
or
utimes(2),
attempt to preserve the access time of files analyzed.
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.
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(3))
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_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.
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/file/magic.
magic_load ();
adds ".mime" and/or ".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(2),
or
utimes(2)
when
MAGIC_PRESERVE_ATIME
is set.
