libmagic(3) - Linux manual page (original) (raw)
LIBMAGIC(3) Library Functions Manual LIBMAGIC(3)
NAME top
**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 libraryLIBRARY top
Magic Number Recognition Library (libmagic, -lmagic)SYNOPSIS top
<_magic.h_> _magict_ **magic_open**(_int flags_) _void_ **magic_close**(_magict_
_cookie_) _const char *_ **magic_error**(_magict cookie_) _int_
**magic_errno**(_magict cookie_) _const char *_ **magic_descriptor**(_magict_
_cookie_, _int fd_) _const char *_ **magic_file**(_magict cookie_, _const char_
_*filename_) _const char *_ **magic_buffer**(_magict cookie_, _const void_
_*buffer_, _sizet length_) _int_ **magic_getflags**(_magict cookie_) _int_
**magic_setflags**(_magict cookie_, _int flags_) _int_ **magic_check**(_magict_
_cookie_, _const char *filename_) _int_ **magic_compile**(_magict cookie_,
_const char *filename_) _int_ **magic_list**(_magict cookie_, _const char_
_*filename_) _int_ **magic_load**(_magict cookie_, _const char *filename_)
_int_ **magic_load_buffers**(_magict cookie_, _void **buffers_, _sizet_
_*sizes_, _sizet nbuffers_) _int_ **magic_getparam**(_magict cookie_, _int_
_param_, _void *value_) _int_ **magic_setparam**(_magict cookie_, _int param_,
_const void *value_) _int_ **magic_version**(_void_) _const char *_
**magic_getpath**(_const char *magicfile_, _int action_)DESCRIPTION top
These functions operate on the magic database file which is
described in _magic_(4).
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_(4) 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](../man3/errno.3.html)_(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_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 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 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 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/local/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 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 7340032
**MAGIC_PARAM_ENCODING_MAX** size_t 1048576
**MAGIC_PARAM_ELF_SHSIZE_MAX** size_t 134217728
**MAGIC_PARAM_MAGWARN_MAX** size_t 64
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_PARAM_REGEX_MAX parameter controls the maximum length
for regex searches.
The MAGIC_PARAM_BYTES_MAX parameter controls the maximum number of
bytes to look inside a file.
The MAGIC_PARAM_ENCODING_MAX parameter controls the maximum number
of bytes to scan for encoding detection.
The MAGIC_PARAM_ELF_SHSIZE_MAX parameter controls the maximum
number of bytes in an elf section.
The MAGIC_PARAM_MAGWARN_MAX parameter controls the maximum number
of warnings to tolerate in a magic file.
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 top
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 top
_/usr/local/share/misc/magic_ The non-compiled default magic
database.
_/usr/local/share/misc/magic.mgc_ The compiled default magic
database.SEE ALSO top
_file_(1), _magic_(4)BUGS top
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 top
Måns Rullgård Initial libmagic implementation, and configuration.
Christos Zoulas API cleanup, error code and allocation handling.COLOPHON top
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man-pages@man7.orgGNU December 29, 2023 LIBMAGIC(3)