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257 lines
7.6 KiB
257 lines
7.6 KiB
.\" Copyright (c) 2003-2007 Tim Kientzle
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD: src/lib/libarchive/libarchive.3,v 1.11 2007/01/09 08:05:56 kientzle Exp $
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.\"
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.Dd February 6, 2010
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.Dt LIBARCHIVE 3
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.Os
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.Sh NAME
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.Nm libarchive
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.Nd functions for reading and writing streaming archives
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.Sh LIBRARY
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.Lb libarchive
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.Sh OVERVIEW
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The
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.Nm
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library provides a flexible interface for reading and writing
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archives in various formats such as tar and cpio.
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.Nm
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also supports reading and writing archives compressed using
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various compression filters such as gzip and bzip2.
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The library is inherently stream-oriented; readers serially iterate through
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the archive, writers serially add things to the archive.
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In particular, note that there is currently no built-in support for
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random access nor for in-place modification.
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.Pp
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When reading an archive, the library automatically detects the
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format and the compression.
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The library currently has read support for:
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.Bl -bullet -compact
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.It
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old-style tar archives,
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.It
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most variants of the POSIX
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.Dq ustar
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format,
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.It
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the POSIX
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.Dq pax interchange
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format,
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.It
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GNU-format tar archives,
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.It
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most common cpio archive formats,
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.It
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ISO9660 CD images (including RockRidge and Joliet extensions),
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.It
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Zip archives.
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.El
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The library automatically detects archives compressed with
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.Xr gzip 1 ,
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.Xr bzip2 1 ,
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.Xr xz 1 ,
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or
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.Xr compress 1
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and decompresses them transparently.
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.Pp
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When writing an archive, you can specify the compression
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to be used and the format to use.
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The library can write
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.Bl -bullet -compact
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.It
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POSIX-standard
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.Dq ustar
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archives,
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.It
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POSIX
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.Dq pax interchange format
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archives,
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.It
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POSIX octet-oriented cpio archives,
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.It
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Zip archive,
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.It
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two different variants of shar archives.
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.El
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Pax interchange format is an extension of the tar archive format that
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eliminates essentially all of the limitations of historic tar formats
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in a standard fashion that is supported
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by POSIX-compliant
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.Xr pax 1
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implementations on many systems as well as several newer implementations of
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.Xr tar 1 .
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Note that the default write format will suppress the pax extended
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attributes for most entries; explicitly requesting pax format will
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enable those attributes for all entries.
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.Pp
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The read and write APIs are accessed through the
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.Fn archive_read_XXX
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functions and the
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.Fn archive_write_XXX
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functions, respectively, and either can be used independently
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of the other.
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.Pp
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The rest of this manual page provides an overview of the library
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operation.
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More detailed information can be found in the individual manual
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pages for each API or utility function.
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.\"
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.Sh READING AN ARCHIVE
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See
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.Xr libarchive_read 3 .
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.\"
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.Sh WRITING AN ARCHIVE
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See
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.Xr libarchive_write 3 .
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.\"
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.Sh WRITING ENTRIES TO DISK
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The
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.Xr archive_write_disk 3
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API allows you to write
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.Xr archive_entry 3
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objects to disk using the same API used by
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.Xr archive_write 3 .
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The
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.Xr archive_write_disk 3
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API is used internally by
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.Fn archive_read_extract ;
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using it directly can provide greater control over how entries
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get written to disk.
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This API also makes it possible to share code between
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archive-to-archive copy and archive-to-disk extraction
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operations.
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.Sh READING ENTRIES FROM DISK
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The
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.Xr archive_read_disk 3
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provides some support for populating
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.Xr archive_entry 3
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objects from information in the filesystem.
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.Sh DESCRIPTION
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Detailed descriptions of each function are provided by the
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corresponding manual pages.
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.Pp
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All of the functions utilize an opaque
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.Tn struct archive
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datatype that provides access to the archive contents.
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.Pp
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The
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.Tn struct archive_entry
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structure contains a complete description of a single archive
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entry.
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It uses an opaque interface that is fully documented in
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.Xr archive_entry 3 .
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.Pp
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Users familiar with historic formats should be aware that the newer
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variants have eliminated most restrictions on the length of textual fields.
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Clients should not assume that filenames, link names, user names, or
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group names are limited in length.
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In particular, pax interchange format can easily accommodate pathnames
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in arbitrary character sets that exceed
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.Va PATH_MAX .
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.Sh RETURN VALUES
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Most functions return
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.Cm ARCHIVE_OK
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(zero) on success, non-zero on error.
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The return value indicates the general severity of the error, ranging
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from
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.Cm ARCHIVE_WARN ,
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which indicates a minor problem that should probably be reported
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to the user, to
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.Cm ARCHIVE_FATAL ,
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which indicates a serious problem that will prevent any further
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operations on this archive.
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On error, the
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.Fn archive_errno
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function can be used to retrieve a numeric error code (see
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.Xr errno 2 ) .
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The
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.Fn archive_error_string
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returns a textual error message suitable for display.
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.Pp
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.Fn archive_read_new
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and
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.Fn archive_write_new
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return pointers to an allocated and initialized
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.Tn struct archive
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object.
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.Pp
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.Fn archive_read_data
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and
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.Fn archive_write_data
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return a count of the number of bytes actually read or written.
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A value of zero indicates the end of the data for this entry.
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A negative value indicates an error, in which case the
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.Fn archive_errno
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and
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.Fn archive_error_string
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functions can be used to obtain more information.
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.Sh ENVIRONMENT
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There are character set conversions within the
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.Xr archive_entry 3
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functions that are impacted by the currently-selected locale.
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.Sh SEE ALSO
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.Xr tar 1 ,
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.Xr archive_entry 3 ,
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.Xr archive_read 3 ,
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.Xr archive_util 3 ,
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.Xr archive_write 3 ,
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.Xr tar 5
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.Sh HISTORY
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The
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.Nm libarchive
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library first appeared in
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.Fx 5.3 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm libarchive
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library was written by
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.An Tim Kientzle Aq kientzle@acm.org .
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.Sh BUGS
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Some archive formats support information that is not supported by
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.Tn struct archive_entry .
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Such information cannot be fully archived or restored using this library.
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This includes, for example, comments, character sets,
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or the arbitrary key/value pairs that can appear in
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pax interchange format archives.
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.Pp
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Conversely, of course, not all of the information that can be
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stored in an
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.Tn struct archive_entry
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is supported by all formats.
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For example, cpio formats do not support nanosecond timestamps;
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old tar formats do not support large device numbers.
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.Pp
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The
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.Xr archive_read_disk 3
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API should support iterating over filesystems;
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that would make it possible to share code among
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disk-to-archive, archive-to-archive, archive-to-disk,
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and disk-to-disk operations.
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Currently, it only supports reading the
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information for a single file.
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(Which is still quite useful, as it hides a lot
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of system-specific details.)
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