libmagic (3) - Linux Manuals

Command to display libmagic manual in Linux: $ man 3 libmagic

NAME

magic_open magic_close magic_error magic_descriptor magic_buffer magic_setflags magic_check magic_compile magic_load - Magic number recognition library

LIBRARY

Lb libmagic

SYNOPSIS

In magic.h Ft magic_t Fn magic_open int flags Ft void Fn magic_close magic_t cookie Ft const char * Fn magic_error magic_t cookie Ft int Fn magic_errno magic_t cookie Ft const char * Fn magic_descriptor magic_t cookie int fd Ft const char * Fn magic_file magic_t cookie const char *filename Ft const char * Fn magic_buffer magic_t cookie const void *buffer size_t length Ft int Fn magic_setflags magic_t cookie int flags Ft int Fn magic_check magic_t cookie const char *filename Ft int Fn magic_compile magic_t cookie const char *filename Ft int Fn magic_list magic_t cookie const char *filename Ft int Fn 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 Fn 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 Fn magic_close function closes the magic(5) database and deallocates any resources used.

The Fn magic_error function returns a textual explanation of the last error, or NULL if there was no error.

The Fn magic_errno function returns the last operating system error number (errno(2) ) that was encountered by a system call.

The Fn 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 Fn magic_descriptor function returns a textual description of the contents of the fd argument, or NULL if an error occurred.

The Fn magic_buffer function returns a textual description of the contents of the buffer argument with length bytes size.

The Fn magic_setflags function sets the flags described above. Note that using both MIME flags together can also return extra information on the charset.

The Fn 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 Fn 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 Fn 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 Fa filename argument which is a colon separated list of database files, or NULL for the default database.

The Fn 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. Fn magic_load adds ``.mgc'' to the database filename as appropriate.

RETURN VALUES

The function Fn magic_open returns a magic cookie on success and NULL on failure setting errno to an appropriate value. It will set errno to Er EINVAL if an unsupported value for flags was given. The Fn magic_list , Fn magic_load , Fn magic_compile , and Fn magic_check functions return 0 on success and -1 on failure. The Fn magic_buffer , Fn magic_getpath , and Fn magic_file , functions return a string on success and NULL on failure. The Fn magic_error function returns a textual description of the errors of the above functions, or NULL if there was no error. Finally, Fn 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.

AUTHORS

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