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ARCHIVE_READ_DISK(3)       Library Functions Manual       ARCHIVE_READ_DISK(3)

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 atrribute
                     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 defaut, moint 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.

NetBSD 8.99.34                   April 3, 2017                  NetBSD 8.99.34