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diff --git a/archivers/libarchive/files/doc/text/libarchive-formats.5.txt b/archivers/libarchive/files/doc/text/libarchive-formats.5.txt index 62df74916e9..60694778b66 100644 --- a/archivers/libarchive/files/doc/text/libarchive-formats.5.txt +++ b/archivers/libarchive/files/doc/text/libarchive-formats.5.txt @@ -1,16 +1,16 @@ -libarchive-formats(5) NetBSD File Formats Manual libarchive-formats(5) +LIBARCHIVE-FORMATS(5) BSD File Formats Manual LIBARCHIVE-FORMATS(5) NAME - libarchive-formats -- archive formats supported by the libarchive library + libarchive-formats — archive formats supported by the libarchive library DESCRIPTION The libarchive(3) library reads and writes a variety of streaming archive formats. Generally speaking, all of these archive formats consist of a - series of ``entries''. Each entry stores a single file system object, - such as a file, directory, or symbolic link. + series of “entries”. Each entry stores a single file system object, such + as a file, directory, or symbolic link. The following provides a brief description of each format supported by - libarchive, with some information about recognized extensions or limita- + libarchive, with some information about recognized extensions or limita‐ tions of the current library support. Note that just because a format is supported by libarchive does not imply that a program that uses libarchive will support that format. Applications that use libarchive @@ -18,8 +18,9 @@ DESCRIPTION libarchive convenience functions to enable all supported formats. Tar Formats - The libarchive(3) library can read most tar archives. However, it only - writes POSIX-standard ``ustar'' and ``pax interchange'' formats. + The libarchive(3) library can read most tar archives. It can write + POSIX-standard “ustar” and “pax interchange” formats as well as v7 tar + format and a subset of the legacy GNU tar format. All tar formats store each entry in one or more 512-byte records. The first record is used for file metadata, including filename, timestamp, @@ -29,59 +30,86 @@ DESCRIPTION storing special entries that modify the interpretation of subsequent entries. - gnutar The libarchive(3) library can read GNU-format tar archives. It - currently supports the most popular GNU extensions, including + gnutar The libarchive(3) library can read most GNU-format tar archives. + It currently supports the most popular GNU extensions, including modern long filename and linkname support, as well as atime and ctime data. The libarchive library does not support multi-volume archives, nor the old GNU long filename format. It can read GNU - sparse file entries, including the new POSIX-based formats, but - cannot write GNU sparse file entries. + sparse file entries, including the new POSIX-based formats. + + The libarchive(3) library can write GNU tar format, including + long filename and linkname support, as well as atime and ctime + data. pax The libarchive(3) library can read and write POSIX-compliant pax interchange format archives. Pax interchange format archives are an extension of the older ustar format that adds a separate entry with additional attributes stored as key/value pairs immediately - before each regular entry. The presence of these additional + before each regular entry. The presence of these additional entries is the only difference between pax interchange format and the older ustar format. The extended attributes are of unlimited length and are stored as UTF-8 Unicode strings. Keywords defined in the standard are in all lowercase; vendors are allowed to define custom keys by preceding them with the vendor name in all - uppercase. When writing pax archives, libarchive uses many of - the SCHILY keys defined by Joerg Schilling's ``star'' archiver - and a few LIBARCHIVE keys. The libarchive library can read most - of the SCHILY keys and most of the GNU keys introduced by GNU - tar. It silently ignores any keywords that it does not under- - stand. + uppercase. When writing pax archives, libarchive uses many of + the SCHILY keys defined by Joerg Schilling's “star” archiver and + a few LIBARCHIVE keys. The libarchive library can read most of + the SCHILY keys and most of the GNU keys introduced by GNU tar. + It silently ignores any keywords that it does not understand. + + The pax interchange format converts filenames to Unicode and + stores them using the UTF-8 encoding. Prior to libarchive 3.0, + libarchive erroneously assumed that the system wide-character + routines natively supported Unicode. This caused it to mis-han‐ + dle non-ASCII filenames on systems that did not satisfy this + assumption. restricted pax The libarchive library can also write pax archives in which it - attempts to suppress the extended attributes entry whenever pos- + attempts to suppress the extended attributes entry whenever pos‐ sible. The result will be identical to a ustar archive unless the extended attributes entry is required to store a long file name, long linkname, extended ACL, file flags, or if any of the standard ustar data (user name, group name, UID, GID, etc) cannot be fully represented in the ustar header. In all cases, the - result can be dearchived by any program that can read POSIX-com- + result can be dearchived by any program that can read POSIX-com‐ pliant pax interchange format archives. Programs that correctly - read ustar format (see below) will also be able to read this for- + read ustar format (see below) will also be able to read this for‐ mat; any extended attributes will be extracted as separate files stored in PaxHeader directories. ustar The libarchive library can both read and write this format. This format has the following limitations: - Device major and minor numbers are limited to 21 bits. Nodes + · Device major and minor numbers are limited to 21 bits. Nodes with larger numbers will not be added to the archive. - Path names in the archive are limited to 255 bytes. (Shorter + · Path names in the archive are limited to 255 bytes. (Shorter if there is no / character in exactly the right place.) - Symbolic links and hard links are stored in the archive with + · Symbolic links and hard links are stored in the archive with + the name of the referenced file. This name is limited to 100 + bytes. + · Extended attributes, file flags, and other extended security + information cannot be stored. + · Archive entries are limited to 8 gigabytes in size. + Note that the pax interchange format has none of these restric‐ + tions. The ustar format is old and widely supported. It is rec‐ + ommended when compatibility is the primary concern. + + v7 The libarchive library can read and write the legacy v7 tar for‐ + mat. This format has the following limitations: + · Only regular files, directories, and symbolic links can be + archived. Block and character device nodes, FIFOs, and sock‐ + ets cannot be archived. + · Path names in the archive are limited to 100 bytes. + · Symbolic links and hard links are stored in the archive with the name of the referenced file. This name is limited to 100 bytes. - Extended attributes, file flags, and other extended security + · User and group information are stored as numeric IDs; there + is no provision for storing user or group names. + · Extended attributes, file flags, and other extended security information cannot be stored. - Archive entries are limited to 8 gigabytes in size. - Note that the pax interchange format has none of these restric- - tions. + · Archive entries are limited to 8 gigabytes in size. + Generally, users should prefer the ustar format for portability + as the v7 tar format is both less useful and less portable. The libarchive library also reads a variety of commonly-used extensions to the basic tar format. These extensions are recognized automatically @@ -93,7 +121,7 @@ DESCRIPTION Libarchive allows these fields to be written without terminator characters. This extends the allowable range; in particular, ustar archives with this extension can support entries up to 64 - gigabytes in size. Libarchive also recognizes base-256 values in + gigabytes in size. Libarchive also recognizes base-256 values in most numeric fields. This essentially removes all limitations on file size, modification time, and device numbers. @@ -103,35 +131,36 @@ DESCRIPTION style ACLs; the newer NFSv4 ACLs are recognized but discarded. The first tar program appeared in Seventh Edition Unix in 1979. The - first official standard for the tar file format was the ``ustar'' (Unix + first official standard for the tar file format was the “ustar” (Unix Standard Tar) format defined by POSIX in 1988. POSIX.1-2001 extended the - ustar format to create the ``pax interchange'' format. + ustar format to create the “pax interchange” format. Cpio Formats The libarchive library can read a number of common cpio variants and can - write ``odc'' and ``newc'' format archives. A cpio archive stores each - entry as a fixed-size header followed by a variable-length filename and - variable-length data. Unlike the tar format, the cpio format does only - minimal padding of the header or file data. There are several cpio vari- - ants, which differ primarily in how they store the initial header: some - store the values as octal or hexadecimal numbers in ASCII, others as - binary values of varying byte order and length. + write “odc” and “newc” format archives. A cpio archive stores each entry + as a fixed-size header followed by a variable-length filename and vari‐ + able-length data. Unlike the tar format, the cpio format does only mini‐ + mal padding of the header or file data. There are several cpio variants, + which differ primarily in how they store the initial header: some store + the values as octal or hexadecimal numbers in ASCII, others as binary + values of varying byte order and length. binary The libarchive library transparently reads both big-endian and - little-endian variants of the original binary cpio format. This + little-endian variants of the original binary cpio format. This format used 32-bit binary values for file size and mtime, and 16-bit binary values for the other fields. - odc The libarchive library can both read and write this POSIX-stan- - dard format, which is officially known as the ``cpio interchange - format'' or the ``octet-oriented cpio archive format'' and some- - times unofficially referred to as the ``old character format''. - This format stores the header contents as octal values in ASCII. - It is standard, portable, and immune from byte-order confusion. + odc The libarchive library can both read and write this POSIX-stan‐ + dard format, which is officially known as the “cpio interchange + format” or the “octet-oriented cpio archive format” and sometimes + unofficially referred to as the “old character format”. This + format stores the header contents as octal values in ASCII. It + is standard, portable, and immune from byte-order confusion. File sizes and mtime are limited to 33 bits (8GB file size), other fields are limited to 18 bits. - SVR4 The libarchive library can read both CRC and non-CRC variants of + SVR4/newc + The libarchive library can read both CRC and non-CRC variants of this format. The SVR4 format uses eight-digit hexadecimal values for all header fields. This limits file size to 4GB, and also limits the mtime and other fields to 32 bits. The SVR4 format @@ -143,33 +172,33 @@ DESCRIPTION of AT&T in 1981. This makes cpio older than tar, although cpio was not included in Version 7 AT&T Unix. As a result, the tar command became much better known in universities and research groups that used Version - 7. The combination of the find and cpio utilities provided very precise - control over file selection. Unfortunately, the format has many limita- + 7. The combination of the find and cpio utilities provided very precise + control over file selection. Unfortunately, the format has many limita‐ tions that make it unsuitable for widespread use. Only the POSIX format permits files over 4GB, and its 18-bit limit for most other fields makes it unsuitable for modern systems. In addition, cpio formats only store numeric UID/GID values (not usernames and group names), which can make it - very difficult to correctly transfer archives across systems with dissim- + very difficult to correctly transfer archives across systems with dissim‐ ilar user numbering. Shar Formats - A ``shell archive'' is a shell script that, when executed on a POSIX-com- + A “shell archive” is a shell script that, when executed on a POSIX-com‐ pliant system, will recreate a collection of file system objects. The libarchive library can write two different kinds of shar archives: shar The traditional shar format uses a limited set of POSIX commands, including echo(1), mkdir(1), and sed(1). It is suitable for - portably archiving small collections of plain text files. How- + portably archiving small collections of plain text files. How‐ ever, it is not generally well-suited for large archives (many implementations of sh(1) have limits on the size of a script) nor should it be used with non-text files. shardump This format is similar to shar but encodes files using - uuencode(1) so that the result will be a plain text file regard- - less of the file contents. It also includes additional shell + uuencode(1) so that the result will be a plain text file regard‐ + less of the file contents. It also includes additional shell commands that attempt to reproduce as many file attributes as - possible, including owner, mode, and flags. The additional com- + possible, including owner, mode, and flags. The additional com‐ mands used to restore file attributes make shardump archives less portable than plain shar archives. @@ -179,63 +208,126 @@ DESCRIPTION CDROM just in order to read the files contained in an ISO9660 image. It also avoids security and complexity issues that come with virtual mounts and loopback devices. Libarchive supports the most common Rockridge - extensions and has partial support for Joliet extensions. If both exten- + extensions and has partial support for Joliet extensions. If both exten‐ sions are present, the Joliet extensions will be used and the Rockridge extensions will be ignored. In particular, this can create problems with hardlinks and symlinks, which are supported by Rockridge but not by Joliet. + Libarchive reads ISO9660 images using a streaming strategy. This allows + it to read compressed images directly (decompressing on the fly) and + allows it to read images directly from network sockets, pipes, and other + non-seekable data sources. This strategy works well for optimized + ISO9660 images created by many popular programs. Such programs collect + all directory information at the beginning of the ISO9660 image so it can + be read from a physical disk with a minimum of seeking. However, not all + ISO9660 images can be read in this fashion. + + Libarchive can also write ISO9660 images. Such images are fully opti‐ + mized with the directory information preceding all file data. This is + done by storing all file data to a temporary file while collecting direc‐ + tory information in memory. When the image is finished, libarchive + writes out the directory structure followed by the file data. The loca‐ + tion used for the temporary file can be changed by the usual environment + variables. + Zip format Libarchive can read and write zip format archives that have uncompressed - entries and entries compressed with the ``deflate'' algorithm. Older zip + entries and entries compressed with the “deflate” algorithm. Other zip compression algorithms are not supported. It can extract jar archives, - archives that use Zip64 extensions and many self-extracting zip archives. - Libarchive reads Zip archives as they are being streamed, which allows it - to read archives of arbitrary size. It currently does not use the cen- - tral directory; this limits libarchive's ability to support some self- - extracting archives and ones that have been modified in certain ways. + archives that use Zip64 extensions and self-extracting zip archives. + Libarchive can use either of two different strategies for reading Zip ar‐ + chives: a streaming strategy which is fast and can handle extremely large + archives, and a seeking strategy which can correctly process self- + extracting Zip archives and archives with deleted members or other in- + place modifications. + + The streaming reader processes Zip archives as they are read. It can + read archives of arbitrary size from tape or network sockets, and can + decode Zip archives that have been separately compressed or encoded. + However, self-extracting Zip archives and archives with certain types of + modifications cannot be correctly handled. Such archives require that + the reader first process the Central Directory, which is ordinarily + located at the end of a Zip archive and is thus inaccessible to the + streaming reader. If the program using libarchive has enabled seek sup‐ + port, then libarchive will use this to processes the central directory + first. + + In particular, the seeking reader must be used to correctly handle self- + extracting archives. Such archives consist of a program followed by a + regular Zip archive. The streaming reader cannot parse the initial pro‐ + gram portion, but the seeking reader starts by reading the Central Direc‐ + tory from the end of the archive. Similarly, Zip archives that have been + modified in-place can have deleted entries or other garbage data that can + only be accurately detected by first reading the Central Directory. Archive (library) file format The Unix archive format (commonly created by the ar(1) archiver) is a general-purpose format which is used almost exclusively for object files - to be read by the link editor ld(1). The ar format has never been stan- + to be read by the link editor ld(1). The ar format has never been stan‐ dardised. There are two common variants: the GNU format derived from SVR4, and the BSD format, which first appeared in 4.4BSD. The two differ primarily in their handling of filenames longer than 15 characters: the GNU/SVR4 variant writes a filename table at the beginning of the archive; the BSD format stores each long filename in an extension area adjacent to - the entry. Libarchive can read both extensions, including archives that + the entry. Libarchive can read both extensions, including archives that may include both types of long filenames. Programs using libarchive can - write GNU/SVR4 format if they provide a filename table to be written into - the archive before any of the entries. Any entries whose names are not - in the filename table will be written using BSD-style long filenames. - This can cause problems for programs such as GNU ld that do not support - the BSD-style long filenames. + write GNU/SVR4 format if they provide an entry called // containing a + filename table to be written into the archive before any of the entries. + Any entries whose names are not in the filename table will be written + using BSD-style long filenames. This can cause problems for programs + such as GNU ld that do not support the BSD-style long filenames. mtree Libarchive can read and write files in mtree(5) format. This format is not a true archive format, but rather a textual description of a file hierarchy in which each line specifies the name of a file and provides - specific metadata about that file. Libarchive can read all of the key- - words supported by both the NetBSD and FreeBSD versions of mtree(1), + specific metadata about that file. Libarchive can read all of the key‐ + words supported by both the NetBSD and FreeBSD versions of mtree(8), although many of the keywords cannot currently be stored in an archive_entry object. When writing, libarchive supports use of the archive_write_set_options(3) interface to specify which keywords should - be included in the output. If libarchive was compiled with access to + be included in the output. If libarchive was compiled with access to suitable cryptographic libraries (such as the OpenSSL libraries), it can compute hash entries such as sha512 or md5 from file data being written to the mtree writer. When reading an mtree file, libarchive will locate the corresponding - files on disk using the contents keyword if present or the regular file- + files on disk using the contents keyword if present or the regular file‐ name. If it can locate and open the file on disk, it will use that to fill in any metadata that is missing from the mtree file and will read the file contents and return those to the program using libarchive. If it cannot locate and open the file on disk, libarchive will return an error for any attempt to read the entry body. + 7-Zip + Libarchive can read and write 7-Zip format archives. TODO: Need more + information + + CAB + Libarchive can read Microsoft Cabinet ( “CAB”) format archives. TODO: + Need more information. + + LHA + TODO: Information about libarchive's LHA support + + RAR + Libarchive has limited support for reading RAR format archives. Cur‐ + rently, libarchive can read RARv3 format archives which have been either + created uncompressed, or compressed using any of the compression methods + supported by the RARv3 format. Libarchive can also read self-extracting + RAR archives. + + Warc + Libarchive can read and write “web archives”. TODO: Need more informa‐ + tion + + XAR + Libarchive can read and write the XAR format used by many Apple tools. + TODO: Need more information + SEE ALSO ar(1), cpio(1), mkisofs(1), shar(1), tar(1), zip(1), zlib(3), cpio(5), mtree(5), tar(5) -NetBSD 5.0 December 27, 2009 NetBSD 5.0 +BSD March 18, 2012 BSD |