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.TH TAR 1
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.SH NAME
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tar, dircp \- archiver
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.SH SYNOPSIS
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.B tar
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.I key
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[
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.I file ...
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]
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.PP
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.B dircp
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.I fromdir
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.I todir
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.SH DESCRIPTION
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.I Tar
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saves and restores file trees.
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It is most often used to transport a tree of files from one
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system to another.
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The
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.I key
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is a string that contains
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at most one function letter plus optional modifiers.
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Other arguments to the command are names of
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files or directories to be dumped or restored.
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A directory name implies all the contained
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files and subdirectories (recursively).
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.PP
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The function is one of the following letters:
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.TP
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.B  c
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Create a new archive with the given files as contents.
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.TP
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.B  r
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The named files
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are appended to the archive.
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.TP
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.B  t
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List all occurrences of each
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.I file
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in the archive, or of all files if there are no
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.I file
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arguments.
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.TP
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.B  x
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Extract the named files from the archive.
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If a file is a directory, the directory is extracted recursively.
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Modes are restored if possible.
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If no file argument is given, extract the entire archive.
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If the archive contains multiple entries for a file,
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the latest one wins.
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.PP
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The modifiers are:
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.TP
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.B f
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Use the next argument as the name of the archive instead of
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the default standard input (for keys
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.B x
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and
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.BR t )
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or standard output (for keys
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.B c
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and
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.BR r ).
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.TP
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.B g
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Use the next (numeric) argument as the group id for files in
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the output archive.
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.TP
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.B i
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Ignore errors encountered when reading.
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Errors writing either produce a corrupt archive
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or indicate deeper file system problems.
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.TP
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.B k
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(keep)
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Modifies the behavior of
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.B x
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not to extract files which already exist.
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.TP
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.B m
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Do not set the modification time on extracted files.
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This is the default behavior; the flag exists only for compatibility with other tars.
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.TP
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.B p
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Create archive in POSIX ustar format,
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which raises the maximum pathname length from 100 to 256 bytes.
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Ustar archives are recognised automatically by
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.I tar
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when reading archives.
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This is the default behavior; the flag exists only for backwards compatibility
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with older versions of tar.
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.TP
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.B P
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Do not generate the POSIX ustar format.
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.TP
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.B R
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When extracting, respect leading slash on file names.
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By default, files are always extracted relative to the current directory.
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.TP
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.B s
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When extracting, attempt to resynchronise after not finding a tape header
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block where expected.
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.TP
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.B T
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Modifies the behavior of
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.B x
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to set the modified time,
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mode and, for POSIX archives and filesystem permitting,
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the user and group
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of each file to that specified in the archive.
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.TP
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.B u
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Use the next (numeric) argument as the user id for files in
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the output archive.  This is only useful when moving files to
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a non-Plan 9 system.
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.TP
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.B v
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(verbose)
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Print the name of each file as it is processed.
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With
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.BR t ,
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give more details about the
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archive entries.
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.TP
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.B z
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Operate on compressed
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.I tar
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archives.
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The type of compression is inferred from the file name extension:
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.IR gzip (1)
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for
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.B .tar.gz
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and
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.BR .tgz ;
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.I bzip2
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(see
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.IR gzip (1))
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for
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.BR .tar.bz ,
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.BR .tbz ,
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.BR .tar.bz2 ,
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and
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.BR .tbz2 ;
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.I compress
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for
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.B .tar.Z
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and
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.BR .tz .
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If no extension matches,
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.I gzip
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is used.
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The
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.B z
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flag is unnecessary (but allowed) when using the
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.B t
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and
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.B x
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verbs on archives with recognized extensions.
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.br
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.ne 6
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.SH EXAMPLES
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.I Tar
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can be used to copy hierarchies thus:
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.IP
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.EX
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@{cd fromdir && tar c .} | @{cd todir && tar xT}
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.EE
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.PP
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.I Dircp
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does this.
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.SH SOURCE
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.B /sys/src/cmd/tar.c
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.br
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.B /rc/bin/dircp
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.SH SEE ALSO
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.IR ar (1),
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.IR bundle (1),
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.IR tapefs (4),
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.IR mkfs (8)
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.SH BUGS
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There is no way to ask for any but the last
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occurrence of a file.
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.PP
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File path names are limited to
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100 characters
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(256 when using ustar format).
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.PP
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The
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.I tar
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format allows specification of links and symbolic links,
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concepts foreign to Plan 9: they are ignored.
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.PP
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The
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.B r
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key (append)
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cannot be used on compressed archives.
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.PP
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.IR Tar ,
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thus
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.IR dircp ,
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doesn't record Plan-9-specific metadata
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such as append-only and exclusive-open permission bits, so they aren't copied.