Manual Reference Pages  - MAGIC (3)

NAME

magic_open, magic_close, magic_error, magic_file, magic_buffer, magic_setflags, magic_check, magic_compile, magic_load - Magic number recognition library.

CONTENTS

Library
Synopsis
Description
Return Values
Files
See Also
Authors

LIBRARY


.Lb libmagic

SYNOPSIS


.In 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_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_load magic_t cookie, const char *filename

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 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.

FILES

/usr/share/file/magic.mime The non-compiled default magic mime database.
/usr/share/file/magic.mime.mgc
  The compiled default magic mime database.
/usr/share/file/magic The non-compiled default magic database.
/usr/share/file/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.


March 22, 2003 MAGIC (3)
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