1.\" $OpenBSD: dd.1,v 1.33 2016/08/17 21:23:01 schwarze Exp $ 2.\" $NetBSD: dd.1,v 1.5 1995/03/21 09:04:04 cgd Exp $ 3.\" 4.\" Copyright (c) 1990, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" This code is derived from software contributed to Berkeley by 8.\" Keith Muller of the University of California, San Diego. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)dd.1 8.2 (Berkeley) 1/13/94 35.\" 36.Dd $Mdocdate: August 17 2016 $ 37.Dt DD 1 38.Os 39.Sh NAME 40.Nm dd 41.Nd convert and copy a file 42.Sh SYNOPSIS 43.Nm dd 44.Op Ar operand ... 45.Sh DESCRIPTION 46The 47.Nm 48utility copies the standard input to the standard output, applying any 49specified conversions. 50Input data is read and written in 512-byte blocks. 51If input reads are short, input from multiple reads are aggregated 52to form the output block. 53When finished, 54.Nm 55displays the number of complete and partial input and output blocks 56and truncated input records to the standard error output. 57.Pp 58The following operands are available: 59.Bl -tag -width of=file 60.It Cm if= Ns Ar file 61Read input from 62.Ar file 63instead of the standard input. 64.It Cm of= Ns Ar file 65Write output to 66.Ar file 67instead of the standard output. 68Any regular output file is truncated unless the 69.Cm notrunc 70conversion value is specified. 71If an initial portion of the output file is skipped (see the 72.Cm seek 73operand), 74the output file is truncated at that point. 75.It Cm ibs= Ns Ar n 76Set the input block size to 77.Ar n 78bytes instead of the default 512. 79.It Cm obs= Ns Ar n 80Set the output block size to 81.Ar n 82bytes instead of the default 512. 83.It Cm bs= Ns Ar n 84Set both the input and output block size to 85.Ar n 86bytes, superseding the 87.Cm ibs 88and 89.Cm obs 90operands. 91If no conversion values other than 92.Cm noerror , 93.Cm notrunc , 94or 95.Cm sync 96are specified, then each input block is copied to the output as a 97single block without any aggregation of short blocks. 98.It Cm cbs= Ns Ar n 99Set the conversion record size to 100.Ar n 101bytes. 102The conversion record size is required by the record oriented conversion 103values. 104.It Cm count= Ns Ar n 105Copy only 106.Ar n 107input blocks. 108.It Cm files= Ns Ar n 109Copy 110.Ar n 111input files before terminating. 112This operand is only applicable when the input device is a tape. 113.It Cm seek= Ns Ar n 114Seek 115.Ar n 116blocks from the beginning of the output before copying. 117On non-tape devices, an 118.Xr lseek 2 119operation is used. 120Otherwise, existing blocks are read and the data discarded. 121If the user does not have read permission for the tape, it is positioned 122using the tape 123.Xr ioctl 2 124function calls. 125If the seek operation is past the end of file, space from the current 126end of file to the specified offset is filled with blocks of NUL bytes. 127.It Cm skip= Ns Ar n 128Skip 129.Ar n 130blocks from the beginning of the input before copying. 131On input which supports seeks, an 132.Xr lseek 2 133operation is used. 134Otherwise, input data is read and discarded. 135For pipes, the correct number of bytes is read. 136For all other devices, the correct number of blocks is read without 137distinguishing between a partial or complete block being read. 138.It Xo 139.Sm off 140.Cm status= Ar value 141.Sm on 142.Xc 143Where 144.Ar value 145is one of the symbols from the following list. 146.Bl -tag -width unblock 147.It Cm noxfer 148Do not print the transfer statistics as the last line of status output. 149.It Cm none 150Do not print the status output. 151Error messages are shown; informational messages are not. 152.El 153.It Xo 154.Sm off 155.Cm conv= Ar value Oo , 156.Sm on 157.Ar value ... Oc 158.Xc 159Where 160.Ar value 161is one of the symbols from the following list. 162.Bl -tag -width unblock 163.It Cm ascii 164The same as the 165.Cm unblock 166value except that characters are translated from EBCDIC to ASCII 167before the records are converted. 168(These values imply 169.Cm unblock 170if the operand 171.Cm cbs 172is also specified.) 173.It Cm block 174Treats the input as a sequence of newline or end-of-file terminated variable 175length records independent of input and output block boundaries. 176Any trailing newline character is discarded. 177Each input record is converted to a fixed length output record where the 178length is specified by the 179.Cm cbs 180operand. 181Input records shorter than the conversion record size are padded with spaces. 182Input records longer than the conversion record size are truncated. 183The number of truncated input records, if any, is reported to the standard 184error output at the completion of the copy. 185.It Cm ebcdic , ibm 186The same as the 187.Cm block 188value except that characters are translated from ASCII to EBCDIC 189after the records are converted. 190(These values imply 191.Cm block 192if the operand 193.Cm cbs 194is also specified.) 195There are two conversion maps for EBCDIC. 196The value 197.Cm ebcdic 198specifies the recommended one which is compatible with 199.At V . 200The value 201.Cm ibm 202is a slightly different mapping, which is compatible with the 203.At V 204.Cm ibm 205value. 206.It Cm lcase 207Transform uppercase characters into lowercase characters. 208.It Cm noerror 209Do not stop processing on an input error. 210When an input error occurs, a diagnostic message followed by the current 211input and output block counts will be written to the standard error output 212in the same format as the standard completion message. 213If the 214.Cm sync 215conversion is also specified, any missing input data will be replaced 216with NUL bytes (or with spaces if a block oriented conversion value was 217specified) and processed as a normal input buffer. 218If the 219.Cm sync 220conversion is not specified, the input block is omitted from the output. 221On input files which are not tapes or pipes, the file offset 222will be positioned past the block in which the error occurred using 223.Xr lseek 2 . 224.It Cm notrunc 225Do not truncate the output file. 226This will preserve any blocks in the output file not explicitly written 227by 228.Nm dd . 229The 230.Cm notrunc 231value is not supported for tapes. 232.It Cm osync 233Pad the final output block to the full output block size. 234If the input file is not a multiple of the output block size 235after conversion, this conversion forces the final output block 236to be the same size as preceding blocks for use on devices that require 237regularly sized blocks to be written. 238This option is incompatible with use of the 239.Cm bs= Ns Ar n 240block size specification. 241.It Cm swab 242Swap every pair of input bytes. 243If an input buffer has an odd number of bytes, the last byte will be 244ignored during swapping. 245.It Cm sync 246Pad every input block to the input buffer size. 247Spaces are used for pad bytes if a block oriented conversion value is 248specified, otherwise NUL bytes are used. 249.It Cm ucase 250Transform lowercase characters into uppercase characters. 251.It Cm unblock 252Treats the input as a sequence of fixed length records independent of input 253and output block boundaries. 254The length of the input records is specified by the 255.Cm cbs 256operand. 257Any trailing space characters are discarded and a newline character is 258appended. 259.El 260.El 261.Pp 262Where sizes are specified, a decimal number of bytes is expected. 263If the number ends with a 264.Sq b , 265.Sq k 266or 267.Sq K , 268.Sq m 269or 270.Sq M , 271.Sq g 272or 273.Sq G , 274or 275.Sq w , 276the number is multiplied by 512, 1024 (1K), 1048576 (1M), 1073741824 (1G), 277or the number of bytes in an integer, respectively. 278Two or more numbers may be separated by an 279.Sq x 280to indicate a product. 281.Pp 282When finished, 283.Nm 284displays the number of complete and partial input and output blocks, 285truncated input records, and odd-length byte-swapping blocks to the 286standard error output. 287A partial input block is one where less than the input block size 288was read. 289A partial output block is one where less than the output block size 290was written. 291Partial output blocks to tape devices are considered fatal errors. 292Otherwise, the rest of the block will be written. 293Partial output blocks to character devices will produce a warning message. 294A truncated input block is one where a variable length record oriented 295conversion value was specified and the input line was too long to 296fit in the conversion record or was not newline terminated. 297.Pp 298Normally, data resulting from input or conversion or both are aggregated 299into output blocks of the specified size. 300After the end of input is reached, any remaining output is written as 301a block. 302This means that the final output block may be shorter than the output 303block size. 304.Pp 305If 306.Nm 307receives a 308.Dv SIGINFO 309(see the 310.Dq status 311argument for 312.Xr stty 1 ) 313signal, the current input and output block counts will 314be written to the standard error output 315in the same format as the standard completion message. 316If 317.Nm 318receives a 319.Dv SIGINT 320signal, the current input and output block counts will 321be written to the standard error output 322in the same format as the standard completion message and 323.Nm 324will exit. 325.Sh EXIT STATUS 326.Ex -std dd 327.Sh EXAMPLES 328Write an 329.Ox 330floppy image to a floppy disk: 331.Pp 332.Dl # dd if=floppy34.fs of=/dev/rfd0c bs=32k 333.Pp 334Create an ISO-9660 image of a CD-ROM: 335.Pp 336.Dl # dd if=/dev/rcd0c of=disk.iso bs=32k 337.Sh SEE ALSO 338.Xr cp 1 , 339.Xr mt 1 , 340.Xr tr 1 341.Sh STANDARDS 342The 343.Nm 344utility is compliant with the 345.St -p1003.1-2008 346specification. 347.Pp 348The conversions 349.Cm ascii , 350.Cm ebcdic , 351and 352.Cm ibm 353are marked by 354.St -p1003.1-2008 355as being an 356X/Open System Interfaces option. 357.Pp 358The 359.Cm files 360and 361.Cm status 362operands, 363the 364.Cm osync 365conversion, 366the 367.Sq K , 368.Sq m , 369.Sq M , 370.Sq g , 371.Sq G , 372and 373.Sq w 374size multipliers 375and 376.Dv SIGINFO 377handling 378are all extensions to the 379.St -p1003.1-2008 380specification. 381.Sh HISTORY 382A 383.Nm 384utility appeared in 385.At v5 . 386