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ARCHIVE_READ_DISK(3)   FreeBSD Library Functions Manual	  ARCHIVE_READ_DISK(3)

NAME
     archive_read_disk_new, archive_read_disk_set_symlink_logical,
     archive_read_disk_set_symlink_physical,
     archive_read_disk_set_symlink_hybrid, archive_read_disk_entry_from_file,
     archive_read_disk_gname, archive_read_disk_uname,
     archive_read_disk_set_uname_lookup, archive_read_disk_set_gname_lookup,
     archive_read_disk_set_standard_lookup, archive_read_close,
     archive_read_finish, archive_read_free -- functions for reading objects
     from disk

LIBRARY
     Streaming Archive Library (libarchive, -larchive)

SYNOPSIS
     #include <archive.h>

     struct archive *
     archive_read_disk_new(void);

     int
     archive_read_disk_set_symlink_logical(struct archive *);

     int
     archive_read_disk_set_symlink_physical(struct archive *);

     int
     archive_read_disk_set_symlink_hybrid(struct archive *);

     int
     archive_read_disk_gname(struct archive *, gid_t);

     int
     archive_read_disk_uname(struct archive *, uid_t);

     int
     archive_read_disk_set_gname_lookup(struct archive *, void *,
	 const char *(*lookup)(void *, gid_t), void (*cleanup)(void *));

     int
     archive_read_disk_set_uname_lookup(struct archive *, void *,
	 const char *(*lookup)(void *, uid_t), void (*cleanup)(void *));

     int
     archive_read_disk_set_standard_lookup(struct archive *);

     int
     archive_read_disk_entry_from_file(struct archive *,
	 struct	archive_entry *, int fd, const struct stat *);

     int
     archive_read_close(struct archive *);

     int
     archive_read_finish(struct	archive	*);

     int
     archive_read_free(struct archive *);

DESCRIPTION
     These functions provide an	API for	reading	information about objects on
     disk.  In particular, they	provide	an interface for populating struct
     archive_entry objects.

     archive_read_disk_new()
	     Allocates and initializes a struct	archive	object suitable	for
	     reading object information	from disk.

     archive_read_disk_set_symlink_logical(),
	     archive_read_disk_set_symlink_physical(),
	     archive_read_disk_set_symlink_hybrid()
	     This sets the mode	used for handling symbolic links.  The
	     ``logical'' mode follows all symbolic links.  The ``physical''
	     mode does not follow any symbolic links.  The ``hybrid'' mode
	     currently behaves identically to the ``logical'' mode.

     archive_read_disk_gname(),	archive_read_disk_uname()
	     Returns a user or group name given	a gid or uid value.  By
	     default, these always return a NULL string.

     archive_read_disk_set_gname_lookup(),
	     archive_read_disk_set_uname_lookup()
	     These allow you to	override the functions used for	user and group
	     name lookups.  You	may also provide a void	* pointer to a private
	     data structure and	a cleanup function for that data.  The cleanup
	     function will be invoked when the struct archive object is
	     destroyed or when new lookup functions are	registered.

     archive_read_disk_set_standard_lookup()
	     This convenience function installs	a standard set of user and
	     group name	lookup functions.  These functions use getpwuid(3) and
	     getgrgid(3) to convert ids	to names, defaulting to	NULL if	the
	     names cannot be looked up.	 These functions also implement	a sim-
	     ple memory	cache to reduce	the number of calls to getpwuid(3) and
	     getgrgid(3).

     archive_read_disk_entry_from_file()
	     Populates a struct	archive_entry object with information about a
	     particular	file.  The archive_entry object	must have already been
	     created with archive_entry_new(3) and at least one	of the source
	     path or path fields must already be set.  (If both	are set, the
	     source path will be used.)

	     Information is read from disk using the path name from the	struct
	     archive_entry object.  If a file descriptor is provided, some
	     information will be obtained using	that file descriptor, on plat-
	     forms that	support	the appropriate	system calls.

	     If	a pointer to a struct stat is provided,	information from that
	     structure will be used instead of reading from the	disk where
	     appropriate.  This	can provide performance	benefits in scenarios
	     where struct stat information has already been read from the disk
	     as	a side effect of some other operation.	(For example, direc-
	     tory traversal libraries often provide this information.)

	     Where necessary, user and group ids are converted to user and
	     group names using the currently registered	lookup functions
	     above.  This affects the file ownership fields and	ACL values in
	     the struct	archive_entry object.

     archive_read_close()
	     Does nothing for archive_read_disk	handles.

     archive_read_finish()
	     This is a deprecated synonym for archive_read_free().

     archive_read_free()
	     Invokes archive_read_close() if it	was not	invoked	manually, then
	     releases all resources.
     More information about the	struct archive object and the overall design
     of	the library can	be found in the	libarchive(3) overview.

EXAMPLE
     The following illustrates basic usage of the library by showing how to
     use it to copy an item on disk into an archive.

	   void
	   file_to_archive(struct archive *a, const char *name)
	   {
	     char buff[8192];
	     size_t bytes_read;
	     struct archive *ard;
	     struct archive_entry *entry;
	     int fd;

	     ard = archive_read_disk_new();
	     archive_read_disk_set_standard_lookup(ard);
	     entry = archive_entry_new();
	     fd	= open(name, O_RDONLY);
	     if	(fd < 0)
		return;
	     archive_entry_copy_pathname(entry,	name);
	     archive_read_disk_entry_from_file(ard, entry, fd, NULL);
	     archive_write_header(a, entry);
	     while ((bytes_read	= read(fd, buff, sizeof(buff)))	> 0)
	       archive_write_data(a, buff, bytes_read);
	     archive_write_finish_entry(a);
	     archive_read_free(ard);
	     archive_entry_free(entry);
	   }

RETURN VALUES
     Most functions return ARCHIVE_OK (zero) on	success, or one	of several
     negative error codes for errors.  Specific	error codes include:
     ARCHIVE_RETRY for operations that might succeed if	retried, ARCHIVE_WARN
     for unusual conditions that do not	prevent	further	operations, and
     ARCHIVE_FATAL for serious errors that make	remaining operations impossi-
     ble.

     archive_read_disk_new() returns a pointer to a newly-allocated struct
     archive object or NULL if the allocation failed for any reason.

     archive_read_disk_gname() and archive_read_disk_uname() return const char
     * pointers	to the textual name or NULL if the lookup failed for any rea-
     son.  The returned	pointer	points to internal storage that	may be reused
     on	the next call to either	of these functions; callers should copy	the
     string if they need to continue accessing it.

ERRORS
     Detailed error codes and textual descriptions are available from the
     archive_errno() and archive_error_string()	functions.

SEE ALSO
     archive_read(3), archive_util(3), archive_write(3),
     archive_write_disk(3), tar(1), libarchive(3)

HISTORY
     The libarchive library first appeared in FreeBSD 5.3.  The
     archive_read_disk interface was added to libarchive 2.6 and first
     appeared in FreeBSD 8.0.

AUTHORS
     The libarchive library was	written	by Tim Kientzle
     <kientzle@FreeBSD.org>.

BUGS
     The ``standard'' user name	and group name lookup functions	are not	the
     defaults because getgrgid(3) and getpwuid(3) are sometimes	too large for
     particular	applications.  The current design allows the application
     author to use a more compact implementation when appropriate.

     The full list of metadata read from disk by
     archive_read_disk_entry_from_file() is necessarily	system-dependent.

     The archive_read_disk_entry_from_file() function reads as much informa-
     tion as it	can from disk.	Some method should be provided to limit	this
     so	that clients who do not	need ACLs, for instance, can avoid the extra
     work needed to look up such information.

     This API should provide a set of methods for walking a directory tree.
     That would	make it	a direct parallel of the archive_read(3) API.  When
     such methods are implemented, the ``hybrid'' symbolic link	mode will make
     sense.

FreeBSD	9.2		       February	2, 2012			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | EXAMPLE | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | AUTHORS | BUGS

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