1.\" Copyright (c) 2003-2007 Tim Kientzle 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD: src/lib/libarchive/libarchive.3,v 1.11 2007/01/09 08:05:56 kientzle Exp $ 26.\" 27.Dd February 6, 2010 28.Dt LIBARCHIVE 3 29.Os 30.Sh NAME 31.Nm libarchive 32.Nd functions for reading and writing streaming archives 33.Sh LIBRARY 34.Lb libarchive 35.Sh OVERVIEW 36The 37.Nm 38library provides a flexible interface for reading and writing 39archives in various formats such as tar and cpio. 40.Nm 41also supports reading and writing archives compressed using 42various compression filters such as gzip and bzip2. 43The library is inherently stream-oriented; readers serially iterate through 44the archive, writers serially add things to the archive. 45In particular, note that there is currently no built-in support for 46random access nor for in-place modification. 47.Pp 48When reading an archive, the library automatically detects the 49format and the compression. 50The library currently has read support for: 51.Bl -bullet -compact 52.It 53old-style tar archives, 54.It 55most variants of the POSIX 56.Dq ustar 57format, 58.It 59the POSIX 60.Dq pax interchange 61format, 62.It 63GNU-format tar archives, 64.It 65most common cpio archive formats, 66.It 67ISO9660 CD images (including RockRidge and Joliet extensions), 68.It 69Zip archives. 70.El 71The library automatically detects archives compressed with 72.Xr gzip 1 , 73.Xr bzip2 1 , 74.Xr xz 1 , 75or 76.Xr compress 1 77and decompresses them transparently. 78.Pp 79When writing an archive, you can specify the compression 80to be used and the format to use. 81The library can write 82.Bl -bullet -compact 83.It 84POSIX-standard 85.Dq ustar 86archives, 87.It 88POSIX 89.Dq pax interchange format 90archives, 91.It 92POSIX octet-oriented cpio archives, 93.It 94Zip archive, 95.It 96two different variants of shar archives. 97.El 98Pax interchange format is an extension of the tar archive format that 99eliminates essentially all of the limitations of historic tar formats 100in a standard fashion that is supported 101by POSIX-compliant 102.Xr pax 1 103implementations on many systems as well as several newer implementations of 104.Xr tar 1 . 105Note that the default write format will suppress the pax extended 106attributes for most entries; explicitly requesting pax format will 107enable those attributes for all entries. 108.Pp 109The read and write APIs are accessed through the 110.Fn archive_read_XXX 111functions and the 112.Fn archive_write_XXX 113functions, respectively, and either can be used independently 114of the other. 115.Pp 116The rest of this manual page provides an overview of the library 117operation. 118More detailed information can be found in the individual manual 119pages for each API or utility function. 120.\" 121.Sh READING AN ARCHIVE 122See 123.Xr libarchive_read 3 . 124.\" 125.Sh WRITING AN ARCHIVE 126See 127.Xr libarchive_write 3 . 128.\" 129.Sh WRITING ENTRIES TO DISK 130The 131.Xr archive_write_disk 3 132API allows you to write 133.Xr archive_entry 3 134objects to disk using the same API used by 135.Xr archive_write 3 . 136The 137.Xr archive_write_disk 3 138API is used internally by 139.Fn archive_read_extract ; 140using it directly can provide greater control over how entries 141get written to disk. 142This API also makes it possible to share code between 143archive-to-archive copy and archive-to-disk extraction 144operations. 145.Sh READING ENTRIES FROM DISK 146The 147.Xr archive_read_disk 3 148provides some support for populating 149.Xr archive_entry 3 150objects from information in the filesystem. 151.Sh DESCRIPTION 152Detailed descriptions of each function are provided by the 153corresponding manual pages. 154.Pp 155All of the functions utilize an opaque 156.Tn struct archive 157datatype that provides access to the archive contents. 158.Pp 159The 160.Tn struct archive_entry 161structure contains a complete description of a single archive 162entry. 163It uses an opaque interface that is fully documented in 164.Xr archive_entry 3 . 165.Pp 166Users familiar with historic formats should be aware that the newer 167variants have eliminated most restrictions on the length of textual fields. 168Clients should not assume that filenames, link names, user names, or 169group names are limited in length. 170In particular, pax interchange format can easily accommodate pathnames 171in arbitrary character sets that exceed 172.Va PATH_MAX . 173.Sh RETURN VALUES 174Most functions return 175.Cm ARCHIVE_OK 176(zero) on success, non-zero on error. 177The return value indicates the general severity of the error, ranging 178from 179.Cm ARCHIVE_WARN , 180which indicates a minor problem that should probably be reported 181to the user, to 182.Cm ARCHIVE_FATAL , 183which indicates a serious problem that will prevent any further 184operations on this archive. 185On error, the 186.Fn archive_errno 187function can be used to retrieve a numeric error code (see 188.Xr errno 2 ) . 189The 190.Fn archive_error_string 191returns a textual error message suitable for display. 192.Pp 193.Fn archive_read_new 194and 195.Fn archive_write_new 196return pointers to an allocated and initialized 197.Tn struct archive 198object. 199.Pp 200.Fn archive_read_data 201and 202.Fn archive_write_data 203return a count of the number of bytes actually read or written. 204A value of zero indicates the end of the data for this entry. 205A negative value indicates an error, in which case the 206.Fn archive_errno 207and 208.Fn archive_error_string 209functions can be used to obtain more information. 210.Sh ENVIRONMENT 211There are character set conversions within the 212.Xr archive_entry 3 213functions that are impacted by the currently-selected locale. 214.Sh SEE ALSO 215.Xr tar 1 , 216.Xr archive_entry 3 , 217.Xr archive_read 3 , 218.Xr archive_util 3 , 219.Xr archive_write 3 , 220.Xr tar 5 221.Sh HISTORY 222The 223.Nm libarchive 224library first appeared in 225.Fx 5.3 . 226.Sh AUTHORS 227.An -nosplit 228The 229.Nm libarchive 230library was written by 231.An Tim Kientzle Aq kientzle@acm.org . 232.Sh BUGS 233Some archive formats support information that is not supported by 234.Tn struct archive_entry . 235Such information cannot be fully archived or restored using this library. 236This includes, for example, comments, character sets, 237or the arbitrary key/value pairs that can appear in 238pax interchange format archives. 239.Pp 240Conversely, of course, not all of the information that can be 241stored in an 242.Tn struct archive_entry 243is supported by all formats. 244For example, cpio formats do not support nanosecond timestamps; 245old tar formats do not support large device numbers. 246.Pp 247The 248.Xr archive_read_disk 3 249API should support iterating over filesystems; 250that would make it possible to share code among 251disk-to-archive, archive-to-archive, archive-to-disk, 252and disk-to-disk operations. 253Currently, it only supports reading the 254information for a single file. 255(Which is still quite useful, as it hides a lot 256of system-specific details.) 257