NAME

     archive_read_disk_new, archive_read_disk_set_behavior,
     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 — 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_behavior(struct archive *, int);

     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 *);

     const char *
     archive_read_disk_gname(struct archive *, gid_t);

     const char *
     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 *);

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_behavior()
             Configures various behavior options when reading entries from disk.  The flags field
             consists of a bitwise OR of one or more of the following values:
             ARCHIVE_READDISK_HONOR_NODUMP
                     Skip files and directories with the nodump file attribute (file flag) set.
                     By default, the nodump file attribute is ignored.
             ARCHIVE_READDISK_MAC_COPYFILE
                     Mac OS X specific. Read metadata (ACLs and extended attributes) with
                     copyfile(3).  By default, metadata is read using copyfile(3).
             ARCHIVE_READDISK_NO_ACL
                     Do not read Access Control Lists.  By default, ACLs are read from disk.
             ARCHIVE_READDISK_NO_FFLAGS
                     Do not read file attributes (file flags).  By default, file attributes are
                     read from disk.  See chattr(1) (Linux) or chflags(1) (FreeBSD, Mac OS X) for
                     more information on file attributes.
             ARCHIVE_READDISK_NO_TRAVERSE_MOUNTS
                     Do not traverse mount points.  By default, mount points are traversed.
             ARCHIVE_READDISK_NO_XATTR
                     Do not read extended file attributes (xattrs).  By default, extended file
                     attributes are read from disk.  See xattr(7) (Linux), xattr(2) (Mac OS X),
                     or getextattr(8) (FreeBSD) for more information on extended file attributes.
             ARCHIVE_READDISK_RESTORE_ATIME
                     Restore access time of traversed files.  By default, access time of
                     traversed files is not restored.

     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 simple 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 platforms 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,
             directory 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.
     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 impossible.

     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 reason.  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 information 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.