ARCHIVE_READ_DISK
Section: C Library Functions (3)
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BSD mandoc
NAME
archive_read_disk_new
archive_read_disk_open
archive_read_disk_open_w
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
archive_read_disk_descend
archive_read_disk_can_descend
archive_read_disk_current_filesystem
archive_read_disk_current_filesystem_is_synthetic
archive_read_disk_current_filesystem_is_remote
archive_read_disk_set_matching
archive_read_disk_set_metadata_filter_callback
- functions for reading objects from disk
LIBRARY
Streaming Archive Library (libarchive, -larchive)
SYNOPSIS
In archive.h
Ft struct archive *
Fn archive_read_disk_new void
Ft int
Fn archive_read_disk_open struct archive * const char *
Ft int
Fn archive_read_disk_open_w struct archive * const wchar_t *
Ft int
Fn archive_read_disk_set_behavior struct archive * int
Ft int
Fn archive_read_disk_set_symlink_logical struct archive *
Ft int
Fn archive_read_disk_set_symlink_physical struct archive *
Ft int
Fn archive_read_disk_set_symlink_hybrid struct archive *
Ft const char *
Fn archive_read_disk_gname struct archive * gid_t
Ft const char *
Fn archive_read_disk_uname struct archive * uid_t
Ft int
Fo archive_read_disk_set_gname_lookup
Fa struct archive *
Fa void *
Fa const char *(*lookup)(void *, gid_t)
Fa void (*cleanup)(void *)
Fc Ft int
Fo archive_read_disk_set_uname_lookup
Fa struct archive *
Fa void *
Fa const char *(*lookup)(void *, uid_t)
Fa void (*cleanup)(void *)
Fc Ft int
Fn archive_read_disk_set_standard_lookup struct archive *
Ft int
Fo archive_read_disk_entry_from_file
Fa struct archive *
Fa struct archive_entry *
Fa int fd
Fa const struct stat *
Fc Ft int
Fn archive_read_disk_descend struct archive *
Ft int
Fn archive_read_disk_can_descend struct archive *
Ft int
Fn archive_read_disk_current_filesystem struct archive *
Ft int
Fn archive_read_disk_current_filesystem_is_synthetic struct archive *
Ft int
Fn archive_read_disk_current_filesystem_is_remote struct archive *
Ft int
Fo archive_read_disk_set_matching
Fa struct archive *
Fa struct archive *
Fa void (*excluded_func)(struct archive *, void *, struct archive entry *)
Fa void *
Fc Ft int
Fo archive_read_disk_set_metadata_filter_callback
Fa struct archive *
Fa int (*metadata_filter_func)(struct archive *, void*, struct archive_entry *)
Fa void *
Fc
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.
- Fn archive_read_disk_new
-
Allocates and initializes a
struct archive
object suitable for reading object information from disk.
- Fn archive_read_disk_open
-
Opens the file or directory from the given path and prepares the
struct archive
to read it from disk.
- Fn archive_read_disk_open_w
-
Opens the file or directory from the given path as a wide character string and prepares the
struct archive
to read it from disk.
- Fn 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_READDISK_NO_SPARSE
-
Do not read sparse file information.
By default, sparse file information is read from disk.
-
Fn archive_read_disk_set_symlink_logical ,
Fn archive_read_disk_set_symlink_physical ,
Fn 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.
-
Fn archive_read_disk_gname ,
Fn archive_read_disk_uname
-
- Returns a user or group name given a gid or uid value.
By default, these always return a NULL string.
-
Fn archive_read_disk_set_gname_lookup ,
Fn 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.
- Fn 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).
- Fn 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_new3
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.
- Fn archive_read_disk_descend
-
If the current entry can be descended, this function will mark the directory as the next entry for
archive_read_header3
to visit.
- Fn archive_read_disk_can_descend
-
Returns 1 if the current entry is an unvisited directory and 0 otherwise.
- Fn archive_read_disk_current_filesystem
-
Returns the index of the most recent filesystem entry that has been visited through archive_read_disk
- Fn archive_read_disk_current_filesystem_is_synthetic
-
Returns 1 if the current filesystem is a virtual filesystem. Returns 0 if the current filesystem is not a virtual filesystem. Returns -1 if it is unknown.
- Fn archive_read_disk_current_filesystem_is_remote
-
Returns 1 if the current filesystem is a remote filesystem. Returns 0 if the current filesystem is not a remote filesystem. Returns -1 if it is unknown.
- Fn archive_read_disk_set_matching
-
Allows the caller to set
struct archive
*_ma to compare each entry during
archive_read_header3
calls. If matched based on calls to
archive_match_path_excluded
archive_match_time_excluded
or
archive_match_owner_excluded
then the callback function specified by the _excluded_func parameter will execute. This function will receive data provided to the fourth parameter, void *_client_data.
- Fn archive_read_disk_set_metadata_filter_callback
-
Allows the caller to set a callback function during calls to
archive_read_header3
to filter out metadata for each entry. The callback function receives the
struct archive
object, void* custom filter data, and the
struct archive_entry
If the callback function returns an error, ARCHIVE_RETRY will be returned and the entry will not be further processed.
More information about the
struct archive
object and the overall design of the library can be found in the
libarchive(3)
overview.
EXAMPLES
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.
Fn archive_read_disk_new
returns a pointer to a newly-allocated
struct archive
object or NULL if the allocation failed for any reason.
Fn archive_read_disk_gname
and
Fn 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
Fn archive_errno
and
Fn archive_error_string
functions.
SEE ALSO
tar(1),
archive_read3,
archive_util3,
archive_write3,
archive_write_disk3,
libarchive(3)
HISTORY
The
libarchive
library first appeared in
Fx 5.3 .
The
archive_read_disk
interface was added to
libarchive 2.6
and first appeared in
Fx 8.0 .
AUTHORS
An -nosplit
The
libarchive
library was written by
An Tim Kientzle Aq 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
Fn archive_read_disk_entry_from_file
is necessarily system-dependent.
The
Fn 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_read3
API.
When such methods are implemented, the
``hybrid''
symbolic link mode will make sense.
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- EXAMPLES
-
- RETURN VALUES
-
- ERRORS
-
- SEE ALSO
-
- HISTORY
-
- AUTHORS
-
- BUGS
-
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Time: 16:54:28 GMT, April 19, 2024