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67618a2eac
- Update bunlded libarchive version used on Windows/Mac - Enable requested zstd support while we are at it. Closes #211
321 lines
10 KiB
Text
321 lines
10 KiB
Text
ARCHIVE_READ_DISK(3) manual page
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== NAME ==
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'''archive_read_disk_new''',
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'''archive_read_disk_set_behavior''',
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'''archive_read_disk_set_symlink_logical''',
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'''archive_read_disk_set_symlink_physical''',
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'''archive_read_disk_set_symlink_hybrid''',
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'''archive_read_disk_entry_from_file''',
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'''archive_read_disk_gname''',
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'''archive_read_disk_uname''',
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'''archive_read_disk_set_uname_lookup''',
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'''archive_read_disk_set_gname_lookup''',
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'''archive_read_disk_set_standard_lookup'''
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- functions for reading objects from disk
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== LIBRARY ==
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Streaming Archive Library (libarchive, -larchive)
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== SYNOPSIS ==
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'''<nowiki>#include <archive.h></nowiki>'''
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<br>
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''struct archive *''
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<br>
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'''archive_read_disk_new'''(''void'');
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<br>
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''int''
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<br>
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'''archive_read_disk_set_behavior'''(''struct archive *'', ''int'');
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<br>
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''int''
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<br>
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'''archive_read_disk_set_symlink_logical'''(''struct archive *'');
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<br>
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''int''
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<br>
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'''archive_read_disk_set_symlink_physical'''(''struct archive *'');
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<br>
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''int''
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<br>
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'''archive_read_disk_set_symlink_hybrid'''(''struct archive *'');
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<br>
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''const char *''
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<br>
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'''archive_read_disk_gname'''(''struct archive *'', ''gid_t'');
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<br>
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''const char *''
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<br>
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'''archive_read_disk_uname'''(''struct archive *'', ''uid_t'');
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<br>
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''int''
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<br>
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'''archive_read_disk_set_gname_lookup'''(''struct archive *'', ''void *'', ''const char *(*lookup)(void *, gid_t)'', ''void (*cleanup)(void *)'');
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<br>
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''int''
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<br>
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'''archive_read_disk_set_uname_lookup'''(''struct archive *'', ''void *'', ''const char *(*lookup)(void *, uid_t)'', ''void (*cleanup)(void *)'');
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<br>
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''int''
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<br>
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'''archive_read_disk_set_standard_lookup'''(''struct archive *'');
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<br>
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''int''
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<br>
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'''archive_read_disk_entry_from_file'''(''struct archive *'', ''struct archive_entry *'', ''int fd'', ''const struct stat *'');
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== DESCRIPTION ==
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These functions provide an API for reading information about
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objects on disk.
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In particular, they provide an interface for populating
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'''struct archive_entry'''
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objects.
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<dl>
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<dt>'''archive_read_disk_new'''()</dt><dd>
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Allocates and initializes a
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'''struct archive'''
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object suitable for reading object information from disk.
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</dd><dt>'''archive_read_disk_set_behavior'''()</dt><dd>
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Configures various behavior options when reading entries from disk.
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The flags field consists of a bitwise OR of one or more of the
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following values:
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<dl>
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<dt>'''ARCHIVE_READDISK_HONOR_NODUMP'''</dt><dd>
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Skip files and directories with the nodump file attribute (file flag) set.
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By default, the nodump file attribute is ignored.
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</dd><dt>'''ARCHIVE_READDISK_MAC_COPYFILE'''</dt><dd>
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Mac OS X specific.
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Read metadata (ACLs and extended attributes) with
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[[copyfile(3)|http://www.freebsd.org/cgi/man.cgi?query=copyfile&sektion=3]].
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By default, metadata is read using
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[[copyfile(3)|http://www.freebsd.org/cgi/man.cgi?query=copyfile&sektion=3]].
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</dd><dt>'''ARCHIVE_READDISK_NO_ACL'''</dt><dd>
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Do not read Access Control Lists.
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By default, ACLs are read from disk.
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</dd><dt>'''ARCHIVE_READDISK_NO_FFLAGS'''</dt><dd>
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Do not read file attributes (file flags).
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By default, file attributes are read from disk.
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See
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[[chattr(1)|http://www.freebsd.org/cgi/man.cgi?query=chattr&sektion=1]]
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(Linux)
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or
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[[chflags(1)|http://www.freebsd.org/cgi/man.cgi?query=chflags&sektion=1]]
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(FreeBSD, Mac OS X)
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for more information on file attributes.
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</dd><dt>'''ARCHIVE_READDISK_NO_TRAVERSE_MOUNTS'''</dt><dd>
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Do not traverse mount points.
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By default, mount points are traversed.
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</dd><dt>'''ARCHIVE_READDISK_NO_XATTR'''</dt><dd>
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Do not read extended file attributes (xattrs).
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By default, extended file attributes are read from disk.
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See
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[[xattr(7)|http://www.freebsd.org/cgi/man.cgi?query=xattr&sektion=7]]
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(Linux,)
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[[xattr(2)|http://www.freebsd.org/cgi/man.cgi?query=xattr&sektion=2]]
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(Mac OS X,)
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or
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[[getextattr(8)|http://www.freebsd.org/cgi/man.cgi?query=getextattr&sektion=8]]
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(FreeBSD)
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for more information on extended file attributes.
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</dd><dt>'''ARCHIVE_READDISK_RESTORE_ATIME'''</dt><dd>
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Restore access time of traversed files.
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By default, access time of traversed files is not restored.
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</dd></dl>
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</dd><dt>
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'''archive_read_disk_set_symlink_logical'''(),
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'''archive_read_disk_set_symlink_physical'''(),
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'''archive_read_disk_set_symlink_hybrid'''()
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</dt> <dd>
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This sets the mode used for handling symbolic links.
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The
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"logical"
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mode follows all symbolic links.
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The
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"physical"
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mode does not follow any symbolic links.
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The
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"hybrid"
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mode currently behaves identically to the
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"logical"
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mode.
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</dd><dt>
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'''archive_read_disk_gname'''(),
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'''archive_read_disk_uname'''()
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</dt> <dd>
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Returns a user or group name given a gid or uid value.
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By default, these always return a NULL string.
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</dd><dt>
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'''archive_read_disk_set_gname_lookup'''(),
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'''archive_read_disk_set_uname_lookup'''()
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</dt> <dd>
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These allow you to override the functions used for
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user and group name lookups.
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You may also provide a
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'''void *'''
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pointer to a private data structure and a cleanup function for
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that data.
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The cleanup function will be invoked when the
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'''struct archive'''
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object is destroyed or when new lookup functions are registered.
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</dd><dt>'''archive_read_disk_set_standard_lookup'''()</dt><dd>
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This convenience function installs a standard set of user
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and group name lookup functions.
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These functions use
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[[getpwuid(3)|http://www.freebsd.org/cgi/man.cgi?query=getpwuid&sektion=3]]
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and
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[[getgrgid(3)|http://www.freebsd.org/cgi/man.cgi?query=getgrgid&sektion=3]]
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to convert ids to names, defaulting to NULL if the names cannot
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be looked up.
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These functions also implement a simple memory cache to reduce
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the number of calls to
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[[getpwuid(3)|http://www.freebsd.org/cgi/man.cgi?query=getpwuid&sektion=3]]
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and
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[[getgrgid(3)|http://www.freebsd.org/cgi/man.cgi?query=getgrgid&sektion=3]].
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</dd><dt>'''archive_read_disk_entry_from_file'''()</dt><dd>
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Populates a
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'''struct archive_entry'''
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object with information about a particular file.
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The
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'''archive_entry'''
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object must have already been created with
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[[ManPageArchiveEntryNew3]]
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and at least one of the source path or path fields must already be set.
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(If both are set, the source path will be used.)
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Information is read from disk using the path name from the
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'''struct archive_entry'''
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object.
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If a file descriptor is provided, some information will be obtained using
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that file descriptor, on platforms that support the appropriate
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system calls.
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If a pointer to a
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'''struct stat'''
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is provided, information from that structure will be used instead
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of reading from the disk where appropriate.
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This can provide performance benefits in scenarios where
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'''struct stat'''
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information has already been read from the disk as a side effect
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of some other operation.
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(For example, directory traversal libraries often provide this information.)
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Where necessary, user and group ids are converted to user and group names
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using the currently-registered lookup functions above.
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This affects the file ownership fields and ACL values in the
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'''struct archive_entry'''
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object.
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</dd></dl>
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More information about the
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''struct'' archive
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object and the overall design of the library can be found in the
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[[ManPageLibarchive3]]
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overview.
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== EXAMPLES ==
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The following illustrates basic usage of the library by
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showing how to use it to copy an item on disk into an archive.
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```text
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void
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file_to_archive(struct archive *a, const char *name)
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{
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char buff[8192];
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size_t bytes_read;
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struct archive *ard;
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struct archive_entry *entry;
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int fd;
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ard = archive_read_disk_new();
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archive_read_disk_set_standard_lookup(ard);
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entry = archive_entry_new();
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fd = open(name, O_RDONLY);
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if (fd < 0)
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return;
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archive_entry_copy_pathname(entry, name);
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archive_read_disk_entry_from_file(ard, entry, fd, NULL);
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archive_write_header(a, entry);
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while ((bytes_read = read(fd, buff, sizeof(buff))) > 0)
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archive_write_data(a, buff, bytes_read);
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archive_write_finish_entry(a);
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archive_read_free(ard);
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archive_entry_free(entry);
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}
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```
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== RETURN VALUES ==
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Most functions return
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'''ARCHIVE_OK'''
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(zero) on success, or one of several negative
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error codes for errors.
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Specific error codes include:
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'''ARCHIVE_RETRY'''
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for operations that might succeed if retried,
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'''ARCHIVE_WARN'''
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for unusual conditions that do not prevent further operations, and
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'''ARCHIVE_FATAL'''
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for serious errors that make remaining operations impossible.
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'''archive_read_disk_new'''()
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returns a pointer to a newly-allocated
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'''struct archive'''
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object or NULL if the allocation failed for any reason.
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'''archive_read_disk_gname'''()
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and
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'''archive_read_disk_uname'''()
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return
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'''const char *'''
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pointers to the textual name or NULL if the lookup failed for any reason.
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The returned pointer points to internal storage that
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may be reused on the next call to either of these functions;
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callers should copy the string if they need to continue accessing it.
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== ERRORS ==
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Detailed error codes and textual descriptions are available from the
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'''archive_errno'''()
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and
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'''archive_error_string'''()
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functions.
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== SEE ALSO ==
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[[ManPageBsdtar1]],
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[[ManPageArchiveRead3]],
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[[ManPageArchiveUtil3]],
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[[ManPageArchiveWrite3]],
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[[ManPageArchiveWriteDisk3]],
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[[ManPageLibarchive3]]
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== HISTORY ==
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The
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'''libarchive'''
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library first appeared in
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FreeBSD 5.3.
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The
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'''archive_read_disk'''
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interface was added to
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'''libarchive''' 2.6
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and first appeared in
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FreeBSD 8.0.
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== AUTHORS ==
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The
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'''libarchive'''
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library was written by
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Tim Kientzle <kientzle@FreeBSD.org.>
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== BUGS ==
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The
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"standard"
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user name and group name lookup functions are not the defaults because
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[[getgrgid(3)|http://www.freebsd.org/cgi/man.cgi?query=getgrgid&sektion=3]]
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and
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[[getpwuid(3)|http://www.freebsd.org/cgi/man.cgi?query=getpwuid&sektion=3]]
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are sometimes too large for particular applications.
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The current design allows the application author to use a more
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compact implementation when appropriate.
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The full list of metadata read from disk by
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'''archive_read_disk_entry_from_file'''()
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is necessarily system-dependent.
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The
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'''archive_read_disk_entry_from_file'''()
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function reads as much information as it can from disk.
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Some method should be provided to limit this so that clients who
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do not need ACLs, for instance, can avoid the extra work needed
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to look up such information.
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This API should provide a set of methods for walking a directory tree.
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That would make it a direct parallel of the
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[[ManPageArchiveRead3]]
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API.
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When such methods are implemented, the
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"hybrid"
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symbolic link mode will make sense.
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