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25.\" $FreeBSD$
26.\"
27.Dd March 18, 2012
28.Dt LIBARCHIVE 3
29.Os
30.Sh NAME
31.Nm libarchive
32.Nd functions for reading and writing streaming archives
33.Sh OVERVIEW
34The
35.Nm
36library provides a flexible interface for reading and writing
37archives in various formats such as tar and cpio.
38.Nm
39also supports reading and writing archives compressed using
40various compression filters such as gzip and bzip2.
41The library is inherently stream-oriented; readers serially iterate through
42the archive, writers serially add things to the archive.
43In particular, note that there is currently no built-in support for
44random access nor for in-place modification.
45.Pp
46When reading an archive, the library automatically detects the
47format and the compression.
48The library currently has read support for:
49.Bl -bullet -compact
50.It
51old-style tar archives,
52.It
53most variants of the POSIX
54.Dq ustar
55format,
56.It
57the POSIX
58.Dq pax interchange
59format,
60.It
61GNU-format tar archives,
62.It
63most common cpio archive formats,
64.It
65ISO9660 CD images (including RockRidge and Joliet extensions),
66.It
67Zip archives,
68.It
69ar archives (including GNU/SysV and BSD extensions),
70.It
71Microsoft CAB archives,
72.It
73LHA archives,
74.It
75mtree file tree descriptions,
76.It
77RAR archives,
78.It
79XAR archives.
80.El
81The library automatically detects archives compressed with
82.Xr gzip 1 ,
83.Xr bzip2 1 ,
84.Xr xz 1 ,
85.Xr lzip 1 ,
86or
87.Xr compress 1
88and decompresses them transparently.
89It can similarly detect and decode archives processed with
90.Xr uuencode 1
91or which have an
92.Xr rpm 1
93header.
94.Pp
95When writing an archive, you can specify the compression
96to be used and the format to use.
97The library can write
98.Bl -bullet -compact
99.It
100POSIX-standard
101.Dq ustar
102archives,
103.It
104POSIX
105.Dq pax interchange format
106archives,
107.It
108POSIX octet-oriented cpio archives,
109.It
110Zip archive,
111.It
112two different variants of shar archives,
113.It
114ISO9660 CD images,
115.It
1167-Zip archives,
117.It
118ar archives,
119.It
120mtree file tree descriptions,
121.It
122XAR archives.
123.El
124Pax interchange format is an extension of the tar archive format that
125eliminates essentially all of the limitations of historic tar formats
126in a standard fashion that is supported
127by POSIX-compliant
128.Xr pax 1
129implementations on many systems as well as several newer implementations of
130.Xr tar 1 .
131Note that the default write format will suppress the pax extended
132attributes for most entries; explicitly requesting pax format will
133enable those attributes for all entries.
134.Pp
135The read and write APIs are accessed through the
136.Fn archive_read_XXX
137functions and the
138.Fn archive_write_XXX
139functions, respectively, and either can be used independently
140of the other.
141.Pp
142The rest of this manual page provides an overview of the library
143operation.
144More detailed information can be found in the individual manual
145pages for each API or utility function.
146.\"
147.Sh READING AN ARCHIVE
148See
149.Xr libarchive_read 3 .
150.\"
151.Sh WRITING AN ARCHIVE
152See
153.Xr libarchive_write 3 .
154.\"
155.Sh WRITING ENTRIES TO DISK
156The
157.Xr archive_write_disk 3
158API allows you to write
159.Xr archive_entry 3
160objects to disk using the same API used by
161.Xr archive_write 3 .
162The
163.Xr archive_write_disk 3
164API is used internally by
165.Fn archive_read_extract ;
166using it directly can provide greater control over how entries
167get written to disk.
168This API also makes it possible to share code between
169archive-to-archive copy and archive-to-disk extraction
170operations.
171.Sh READING ENTRIES FROM DISK
172The
173.Xr archive_read_disk 3
174supports for populating
175.Xr archive_entry 3
176objects from information in the filesystem.
177This includes the information accessible from the
178.Xr stat 2
179system call as well as ACLs, extended attributes,
180and other metadata.
181The
182.Xr archive_read_disk 3
183API also supports iterating over directory trees,
184which allows directories of files to be read using
185an API compatible with
186the
187.Xr archive_read 3
188API.
189.Sh DESCRIPTION
190Detailed descriptions of each function are provided by the
191corresponding manual pages.
192.Pp
193All of the functions utilize an opaque
194.Tn struct archive
195datatype that provides access to the archive contents.
196.Pp
197The
198.Tn struct archive_entry
199structure contains a complete description of a single archive
200entry.
201It uses an opaque interface that is fully documented in
202.Xr archive_entry 3 .
203.Pp
204Users familiar with historic formats should be aware that the newer
205variants have eliminated most restrictions on the length of textual fields.
206Clients should not assume that filenames, link names, user names, or
207group names are limited in length.
208In particular, pax interchange format can easily accommodate pathnames
209in arbitrary character sets that exceed
210.Va PATH_MAX .
211.Sh RETURN VALUES
212Most functions return
213.Cm ARCHIVE_OK
214(zero) on success, non-zero on error.
215The return value indicates the general severity of the error, ranging
216from
217.Cm ARCHIVE_WARN ,
218which indicates a minor problem that should probably be reported
219to the user, to
220.Cm ARCHIVE_FATAL ,
221which indicates a serious problem that will prevent any further
222operations on this archive.
223On error, the
224.Fn archive_errno
225function can be used to retrieve a numeric error code (see
226.Xr errno 2 ) .
227The
228.Fn archive_error_string
229returns a textual error message suitable for display.
230.Pp
231.Fn archive_read_new
232and
233.Fn archive_write_new
234return pointers to an allocated and initialized
235.Tn struct archive
236object.
237.Pp
238.Fn archive_read_data
239and
240.Fn archive_write_data
241return a count of the number of bytes actually read or written.
242A value of zero indicates the end of the data for this entry.
243A negative value indicates an error, in which case the
244.Fn archive_errno
245and
246.Fn archive_error_string
247functions can be used to obtain more information.
248.Sh ENVIRONMENT
249There are character set conversions within the
250.Xr archive_entry 3
251functions that are impacted by the currently-selected locale.
252.Sh SEE ALSO
253.Xr tar 1 ,
254.Xr archive_entry 3 ,
255.Xr archive_read 3 ,
256.Xr archive_util 3 ,
257.Xr archive_write 3 ,
258.Xr tar 5
259.Sh HISTORY
260The
261.Nm libarchive
262library first appeared in
263.Fx 5.3 .
264.Sh AUTHORS
265.An -nosplit
266The
267.Nm libarchive
268library was originally written by
269.An Tim Kientzle Aq kientzle@acm.org .
270.Sh BUGS
271Some archive formats support information that is not supported by
272.Tn struct archive_entry .
273Such information cannot be fully archived or restored using this library.
274This includes, for example, comments, character sets,
275or the arbitrary key/value pairs that can appear in
276pax interchange format archives.
277.Pp
278Conversely, of course, not all of the information that can be
279stored in an
280.Tn struct archive_entry
281is supported by all formats.
282For example, cpio formats do not support nanosecond timestamps;
283old tar formats do not support large device numbers.
284.Pp
285The ISO9660 reader cannot yet read all ISO9660 images;
286it should learn how to seek.
287.Pp
288The AR writer requires the client program to use
289two passes, unlike all other libarchive writers.
290