directories that are on different file systems from the current
directory.
+@opsummary{one-top-level}
+@item --one-top-level[=@var{dir}]
+Tells @command{tar} to create a new directory beneath the extraction directory
+(or the one passed to @option{-C}) and use it to guard against
+tarbombs. In the absence of @var{dir} argument, the name of the new directory
+will be equal to the base name of the archive (file name minus the
+archive suffix, if recognized). Any member names that do not begin
+with that directory name (after
+transformations from @option{--transform} and
+@option{--strip-components}) will be prefixed with it. Recognized
+file name suffixes are @samp{.tar}, and any compression suffixes
+recognizable by @xref{--auto-compress}.
+
@opsummary{overwrite}
@item --overwrite
@smallexample
tar (GNU tar) @value{VERSION}
-Copyright (C) 2013 Free Software Foundation, Inc.
+Copyright (C) 2013-2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
tar: Hit write checkpoint #30
@end smallexample
-The complete list of available format specifiers follows:
+The complete list of available format specifiers follows. Some of
+them can take optional arguments. These arguments, if given, are
+supplied in curly braces between the percent sign and the specifier
+letter.
@table @samp
@item %s
@item %u
Print number of the checkpoint.
-@item %T
+@item %@{r,w,d@}T
Print number of bytes transferred so far and approximate transfer
-speed. The number is preceded by @samp{W:}, when writing and by
-@samp{R:} when reading. If @command{tar} is performing delete
-operation (@pxref{delete}), three numbers are printed: number of bytes
-read, written and deleted, each of them prefixed by @samp{R:},
-@samp{W:} and @samp{D:} correspondingy. For example:
+speed. Optional arguments supply prefixes to be used before number
+of bytes read, written and deleted, correspondingly. If absent,
+they default to @samp{R}. @samp{W}, @samp{D}. Any or all of them can
+be omitted, so, that e.g. @samp{%@{@}T} means to print corresponding
+statistics without any prefixes. Any surplus arguments, if present,
+are silently ignored.
@example
$ @kbd{tar --delete -f f.tar --checkpoint-action=echo="#%u: %T" main.c}
-tar: #1: R: 0 (0B, ?/s),W: 0 (0B, ?/s),D: 0
+tar: #1: R: 0 (0B, 0B/s),W: 0 (0B, 0B/s),D: 0
tar: #2: R: 10240 (10KiB, 19MiB/s),W: 0 (0B, 0B/s),D: 10240
@end example
Pad output with spaces to the @var{n}th column. If the
@samp{@{@var{n}@}} part is omitted, the current screen width
is assumed.
+
+@item %@var{c}
+This is a shortcut for @samp{%@{%Y-%m-%d %H:%M:%S@}t: %ds, %@{read,wrote@}T%*\r},
+intended mainly for use with @samp{ttyout} action (see below).
@end table
Aside from format expansion, the message string is subject to