Index: head/bin/dd/dd.1
===================================================================
--- head/bin/dd/dd.1	(revision 306714)
+++ head/bin/dd/dd.1	(revision 306715)
@@ -1,457 +1,462 @@
 .\"-
 .\" Copyright (c) 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
 .\"
 .\" This code is derived from software contributed to Berkeley by
 .\" Keith Muller of the University of California, San Diego.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\" 4. Neither the name of the University nor the names of its contributors
 .\"    may be used to endorse or promote products derived from this software
 .\"    without specific prior written permission.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
 .\"     @(#)dd.1	8.2 (Berkeley) 1/13/94
 .\" $FreeBSD$
 .\"
-.Dd August 25, 2016
+.Dd October 5, 2016
 .Dt DD 1
 .Os
 .Sh NAME
 .Nm dd
 .Nd convert and copy a file
 .Sh SYNOPSIS
 .Nm
 .Op Ar operands ...
 .Sh DESCRIPTION
 The
 .Nm
 utility copies the standard input to the standard output.
 Input data is read and written in 512-byte blocks.
 If input reads are short, input from multiple reads are aggregated
 to form the output block.
 When finished,
 .Nm
 displays the number of complete and partial input and output blocks
 and truncated input records to the standard error output.
 .Pp
 The following operands are available:
 .Bl -tag -width ".Cm of Ns = Ns Ar file"
 .It Cm bs Ns = Ns Ar n
 Set both input and output block size to
 .Ar n
 bytes, superseding the
 .Cm ibs
 and
 .Cm obs
 operands.
 If no conversion values other than
 .Cm noerror ,
 .Cm notrunc
 or
 .Cm sync
 are specified, then each input block is copied to the output as a
 single block without any aggregation of short blocks.
 .It Cm cbs Ns = Ns Ar n
 Set the conversion record size to
 .Ar n
 bytes.
 The conversion record size is required by the record oriented conversion
 values.
 .It Cm count Ns = Ns Ar n
 Copy only
 .Ar n
 input blocks.
 .It Cm files Ns = Ns Ar n
 Copy
 .Ar n
 input files before terminating.
 This operand is only applicable when the input device is a tape.
 .It Cm fillchar Ns = Ns Ar c
 When padding a block in conversion mode or due to use of
 .Cm noerror
 and
 .Cm sync
 modes, fill with the specified
 .Tn ASCII
 character, rather than using a space or
 .Dv NUL .
 .It Cm ibs Ns = Ns Ar n
 Set the input block size to
 .Ar n
 bytes instead of the default 512.
 .It Cm if Ns = Ns Ar file
 Read input from
 .Ar file
 instead of the standard input.
 .It Cm iseek Ns = Ns Ar n
 Seek on the input file
 .Ar n
 blocks.
 This is synonymous with
 .Cm skip Ns = Ns Ar n .
 .It Cm obs Ns = Ns Ar n
 Set the output block size to
 .Ar n
 bytes instead of the default 512.
 .It Cm of Ns = Ns Ar file
 Write output to
 .Ar file
 instead of the standard output.
 Any regular output file is truncated unless the
 .Cm notrunc
 conversion value is specified.
 If an initial portion of the output file is seeked past (see the
 .Cm oseek
 operand),
 the output file is truncated at that point.
 .It Cm oseek Ns = Ns Ar n
 Seek on the output file
 .Ar n
 blocks.
 This is synonymous with
 .Cm seek Ns = Ns Ar n .
 .It Cm seek Ns = Ns Ar n
 Seek
 .Ar n
 blocks from the beginning of the output before copying.
 On non-tape devices, an
 .Xr lseek 2
 operation is used.
 Otherwise, existing blocks are read and the data discarded.
 If the user does not have read permission for the tape, it is positioned
 using the tape
 .Xr ioctl 2
 function calls.
 If the seek operation is past the end of file, space from the current
 end of file to the specified offset is filled with blocks of
 .Dv NUL
 bytes.
 .It Cm skip Ns = Ns Ar n
 Skip
 .Ar n
 blocks from the beginning of the input before copying.
 On input which supports seeks, an
 .Xr lseek 2
 operation is used.
 Otherwise, input data is read and discarded.
 For pipes, the correct number of bytes is read.
 For all other devices, the correct number of blocks is read without
 distinguishing between a partial or complete block being read.
 .It Cm speed Ns = Ns Ar n
 Limit the copying speed to
 .Ar n
 bytes per second.
 .It Cm status Ns = Ns Ar value
 Where
 .Cm value
 is one of the symbols from the following list.
 .Bl -tag -width ".Cm noxfer"
 .It Cm noxfer
 Do not print the transfer statistics as the last line of status output.
 .It Cm none
 Do not print the status output.
 Error messages are shown; informational messages are not.
 .El
 .It Cm conv Ns = Ns Ar value Ns Op , Ns Ar value ...
 Where
 .Cm value
 is one of the symbols from the following list.
 .Bl -tag -width ".Cm unblock"
 .It Cm ascii , oldascii
 The same as the
 .Cm unblock
 value except that characters are translated from
 .Tn EBCDIC
 to
 .Tn ASCII
 before the
 records are converted.
 (These values imply
 .Cm unblock
 if the operand
 .Cm cbs
 is also specified.)
 There are two conversion maps for
 .Tn ASCII .
 The value
 .Cm ascii
 specifies the recommended one which is compatible with
 .At V .
 The value
 .Cm oldascii
 specifies the one used in historic
 .At
 and
 .No pre- Ns Bx 4.3 reno
 systems.
 .It Cm block
 Treats the input as a sequence of newline or end-of-file terminated variable
 length records independent of input and output block boundaries.
 Any trailing newline character is discarded.
 Each input record is converted to a fixed length output record where the
 length is specified by the
 .Cm cbs
 operand.
 Input records shorter than the conversion record size are padded with spaces.
 Input records longer than the conversion record size are truncated.
 The number of truncated input records, if any, are reported to the standard
 error output at the completion of the copy.
 .It Cm ebcdic , ibm , oldebcdic , oldibm
 The same as the
 .Cm block
 value except that characters are translated from
 .Tn ASCII
 to
 .Tn EBCDIC
 after the
 records are converted.
 (These values imply
 .Cm block
 if the operand
 .Cm cbs
 is also specified.)
 There are four conversion maps for
 .Tn EBCDIC .
 The value
 .Cm ebcdic
 specifies the recommended one which is compatible with
 .At V .
 The value
 .Cm ibm
 is a slightly different mapping, which is compatible with the
 .At V
 .Cm ibm
 value.
 The values
 .Cm oldebcdic
 and
 .Cm oldibm
 are maps used in historic
 .At
 and
 .No pre- Ns Bx 4.3 reno
 systems.
 .It Cm lcase
 Transform uppercase characters into lowercase characters.
 .It Cm pareven , parnone , parodd , parset
 Output data with the specified parity.
 The parity bit on input is stripped unless
 .Tn EBCDIC
 to
 .Tn ASCII
 conversions is also specified.
 .It Cm noerror
 Do not stop processing on an input error.
 When an input error occurs, a diagnostic message followed by the current
 input and output block counts will be written to the standard error output
 in the same format as the standard completion message.
 If the
 .Cm sync
 conversion is also specified, any missing input data will be replaced
 with
 .Dv NUL
 bytes (or with spaces if a block oriented conversion value was
 specified) and processed as a normal input buffer.
 If the
 .Cm fillchar
 option is specified, the fill character provided on the command line
 will override
 the automatic selection of the fill character.
 If the
 .Cm sync
 conversion is not specified, the input block is omitted from the output.
 On input files which are not tapes or pipes, the file offset
 will be positioned past the block in which the error occurred using
 .Xr lseek 2 .
 .It Cm notrunc
 Do not truncate the output file.
 This will preserve any blocks in the output file not explicitly written
 by
 .Nm .
 The
 .Cm notrunc
 value is not supported for tapes.
 .It Cm osync
 Pad the final output block to the full output block size.
 If the input file is not a multiple of the output block size
 after conversion, this conversion forces the final output block
 to be the same size as preceding blocks for use on devices that require
 regularly sized blocks to be written.
 This option is incompatible with use of the
 .Cm bs Ns = Ns Ar n
 block size specification.
 .It Cm sparse
 If one or more output blocks would consist solely of
 .Dv NUL
 bytes, try to seek the output file by the required space instead of
 filling them with
 .Dv NUL Ns s ,
 resulting in a sparse file.
 .It Cm swab
 Swap every pair of input bytes.
 If an input buffer has an odd number of bytes, the last byte will be
 ignored during swapping.
 .It Cm sync
 Pad every input block to the input buffer size.
 Spaces are used for pad bytes if a block oriented conversion value is
 specified, otherwise
 .Dv NUL
 bytes are used.
 .It Cm ucase
 Transform lowercase characters into uppercase characters.
 .It Cm unblock
 Treats the input as a sequence of fixed length records independent of input
 and output block boundaries.
 The length of the input records is specified by the
 .Cm cbs
 operand.
 Any trailing space characters are discarded and a newline character is
 appended.
 .El
 .El
 .Pp
 Where sizes or speed are specified, a decimal, octal, or hexadecimal number of
 bytes is expected.
 If the number ends with a
 .Dq Li b ,
 .Dq Li k ,
 .Dq Li m ,
 .Dq Li g ,
 .Dq Li t ,
 .Dq Li p ,
 or
 .Dq Li w ,
 the
 number is multiplied by 512, 1024 (1K), 1048576 (1M), 1073741824 (1G),
 1099511627776 (1T), 1125899906842624 (1P)
 or the number of bytes in an integer, respectively.
 Two or more numbers may be separated by an
 .Dq Li x
 to indicate a product.
 .Pp
 When finished,
 .Nm
 displays the number of complete and partial input and output blocks,
 truncated input records and odd-length byte-swapping blocks to the
 standard error output.
 A partial input block is one where less than the input block size
 was read.
 A partial output block is one where less than the output block size
 was written.
 Partial output blocks to tape devices are considered fatal errors.
 Otherwise, the rest of the block will be written.
 Partial output blocks to character devices will produce a warning message.
 A truncated input block is one where a variable length record oriented
 conversion value was specified and the input line was too long to
 fit in the conversion record or was not newline terminated.
 .Pp
 Normally, data resulting from input or conversion or both are aggregated
 into output blocks of the specified size.
 After the end of input is reached, any remaining output is written as
 a block.
 This means that the final output block may be shorter than the output
 block size.
 .Pp
 If
 .Nm
 receives a
 .Dv SIGINFO
 (see the
 .Cm status
 argument for
 .Xr stty 1 )
 signal, the current input and output block counts will
 be written to the standard error output
 in the same format as the standard completion message.
 If
 .Nm
 receives a
 .Dv SIGINT
 signal, the current input and output block counts will
 be written to the standard error output
 in the same format as the standard completion message and
 .Nm
 will exit.
 .Sh EXIT STATUS
 .Ex -std
 .Sh EXAMPLES
 Check that a disk drive contains no bad blocks:
 .Pp
 .Dl "dd if=/dev/ada0 of=/dev/null bs=1m"
 .Pp
 Do a refresh of a disk drive, in order to prevent presently
 recoverable read errors from progressing into unrecoverable read errors:
 .Pp
 .Dl "dd if=/dev/ada0 of=/dev/ada0 bs=1m"
 .Pp
 Remove parity bit from a file:
 .Pp
 .Dl "dd if=file conv=parnone of=file.txt"
 .Pp
 Check for (even) parity errors on a file:
 .Pp
 .Dl "dd if=file conv=pareven | cmp -x - file"
 .Pp
 To create an image of a Mode-1 CD-ROM, which is a commonly used format
 for data CD-ROM disks, use a block size of 2048 bytes:
 .Pp
 .Dl "dd if=/dev/cd0 of=filename.iso bs=2048"
 .Pp
 Write a filesystem image to a memory stick, padding the end with zeros,
 if necessary, to a 1MiB boundary:
 .Pp
 .Dl "dd if=memstick.img of=/dev/da0 bs=1m conv=noerror,sync"
 .Sh SEE ALSO
 .Xr cp 1 ,
 .Xr mt 1 ,
 .Xr recoverdisk 1 ,
 .Xr tr 1 ,
 .Xr geom 4
 .Sh STANDARDS
 The
 .Nm
 utility is expected to be a superset of the
 .St -p1003.2
 standard.
 The
 .Cm files
 and
 .Cm status
 operands and the
 .Cm ascii ,
 .Cm ebcdic ,
 .Cm ibm ,
 .Cm oldascii ,
 .Cm oldebcdic
 and
 .Cm oldibm
 values are extensions to the
 .Tn POSIX
 standard.
+.Sh HISTORY
+A
+.Nm
+command appeared in
+.At v5 .
 .Sh BUGS
 Protection mechanisms in the
 .Xr geom 4
 subsystem might prevent the super-user from writing blocks to a disk.
 Instructions for temporarily disabling these protection mechanisms can be
 found in the
 .Xr geom 4
 manpage.