1.\" Copyright (c) 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Keith Muller of the University of California, San Diego. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)dd.1 8.2 (Berkeley) 1/13/94 36.\" $Id: dd.1,v 1.7 1998/05/06 06:51:35 charnier Exp $ 37.\" 38.Dd January 13, 1994 39.Dt DD 1 40.Os 41.Sh NAME 42.Nm dd 43.Nd convert and copy a file 44.Sh SYNOPSIS 45.Nm dd 46.Op operands ... 47.Sh DESCRIPTION 48The 49.Nm 50utility copies the standard input to the standard output. 51Input data is read and written in 512-byte blocks. 52If input reads are short, input from multiple reads are aggregated 53to form the output block. 54When finished, 55.Nm 56displays the number of complete and partial input and output blocks 57and truncated input records to the standard error output. 58.Pp 59The following operands are available: 60.Bl -tag -width of=file 61.It Cm bs= Ns Ar n 62Set both input and output block size to 63.Va n 64bytes, superseding the 65.Cm ibs 66and 67.Cm obs 68operands. 69If no conversion values other than 70.Cm noerror , 71.Cm notrunc 72or 73.Cm sync 74are specified, then each input block is copied to the output as a 75single block without any aggregation of short blocks. 76.It Cm cbs= Ns Ar n 77Set the conversion record size to 78.Va n 79bytes. 80The conversion record size is required by the record oriented conversion 81values. 82.It Cm count= Ns Ar n 83Copy only 84.Va n 85input blocks. 86.It Cm files= Ns Ar n 87Copy 88.Va n 89input files before terminating. 90This operand is only applicable when the input device is a tape. 91.It Cm ibs= Ns Ar n 92Set the input block size to 93.Va n 94bytes instead of the default 512. 95.It Cm if= Ns Ar file 96Read input from 97.Ar file 98instead of the standard input. 99.It Cm obs= Ns Ar n 100Set the output block size to 101.Va n 102bytes instead of the default 512. 103.It Cm of= Ns Ar file 104Write output to 105.Ar file 106instead of the standard output. 107Any regular output file is truncated unless the 108.Cm notrunc 109conversion value is specified. 110If an initial portion of the output file is skipped (see the 111.Cm seek 112operand), 113the output file is truncated at that point. 114.It Cm seek= Ns Ar n 115Seek 116.Va n 117blocks from the beginning of the output before copying. 118On non-tape devices, an 119.Xr lseek 2 120operation is used. 121Otherwise, existing blocks are read and the data discarded. 122If the user does not have read permission for the tape, it is positioned 123using the tape 124.Xr ioctl 2 125function calls. 126If the seek operation is past the end of file, space from the current 127end of file to the specified offset is filled with blocks of 128.Tn NUL 129bytes. 130.It Cm skip= Ns Ar n 131Skip 132.Va n 133blocks from the beginning of the input before copying. 134On input which supports seeks, an 135.Xr lseek 2 136operation is used. 137Otherwise, input data is read and discarded. 138For pipes, the correct number of bytes is read. 139For all other devices, the correct number of blocks is read without 140distinguishing between a partial or complete block being read. 141.It Xo 142.Cm conv= 143.Ns Cm value Ns Op \&, Cm value \&... 144.Xc 145Where 146.Cm value 147is one of the symbols from the following list. 148.Bl -tag -width unblock 149.It Cm ascii , oldascii 150The same as the 151.Cm unblock 152value except that characters are translated from 153.Tn EBCDIC 154to 155.Tn ASCII 156before the 157records are converted. 158(These values imply 159.Cm unblock 160if the operand 161.Cm cbs 162is also specified.) 163There are two conversion maps for 164.Tn ASCII . 165The value 166.Cm ascii 167specifies the recommended one which is compatible with System V. 168The value 169.Cm oldascii 170specifies the one used in historic 171.Tn AT&T 172and pre-4.3BSD-reno systems. 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, are reported to the standard 184error output at the completion of the copy. 185.It Cm ebcdic , ibm , oldebcdic , oldibm 186The same as the 187.Cm block 188value except that characters are translated from 189.Tn ASCII 190to 191.Tn EBCDIC 192after the 193records are converted. 194(These values imply 195.Cm block 196if the operand 197.Cm cbs 198is also specified.) 199There are four conversion maps for 200.Tn EBCDIC . 201The value 202.Cm ebcdic 203specifies the recommended one which is compatible with 204.At V . 205The value 206.Cm ibm 207is a slightly different mapping, which is compatible with the 208.At V 209.Cm ibm 210value. 211The values 212.Cm oldebcdic 213and 214.Cm oldibm 215are maps used in historic 216.Tn AT&T 217and pre-4.3BSD-reno systems. 218.It Cm lcase 219Transform uppercase characters into lowercase characters. 220.It Cm noerror 221Do not stop processing on an input error. 222When an input error occurs, a diagnostic message followed by the current 223input and output block counts will be written to the standard error output 224in the same format as the standard completion message. 225If the 226.Cm sync 227conversion is also specified, any missing input data will be replaced 228with 229.Tn NUL 230bytes (or with spaces if a block oriented conversion value was 231specified) and processed as a normal input buffer. 232If the 233.Cm sync 234conversion is not specified, the input block is omitted from the output. 235On input files which are not tapes or pipes, the file offset 236will be positioned past the block in which the error occurred using 237.Xr lseek 2 . 238.It Cm notrunc 239Do not truncate the output file. 240This will preserve any blocks in the output file not explicitly written 241by 242.Nm Ns . 243The 244.Cm notrunc 245value is not supported for tapes. 246.It Cm osync 247Pad the final output block to the full output block size. 248If the input file is not a multiple of the output block size 249after conversion, this conversion forces the final output block 250to be the same size as preceding blocks for use on devices that require 251regularly sized blocks to be written. 252This option is incompatible with use of the 253.Cm bs= Ns Ar n 254block size specification. 255.It Cm sparse 256If one or more output blocks would consist solely of 257.Tn NUL 258bytes, try to seek the output file by the required space instead of 259filling them with 260.Tn NULs , 261resulting in a sparse file. 262.It Cm swab 263Swap every pair of input bytes. 264If an input buffer has an odd number of bytes, the last byte will be 265ignored during swapping. 266.It Cm sync 267Pad every input block to the input buffer size. 268Spaces are used for pad bytes if a block oriented conversion value is 269specified, otherwise 270.Tn NUL 271bytes are used. 272.It Cm ucase 273Transform lowercase characters into uppercase characters. 274.It Cm unblock 275Treats the input as a sequence of fixed length records independent of input 276and output block boundaries. 277The length of the input records is specified by the 278.Cm cbs 279operand. 280Any trailing space characters are discarded and a newline character is 281appended. 282.El 283.El 284.Pp 285Where sizes are specified, a decimal number of bytes is expected. 286If the number ends with a ``b'', ``k'', ``m'' or ``w'', the number 287is multiplied by 512, 1024 (1K), 1048576 (1M) or the number of bytes 288in an integer, respectively. 289Two or more numbers may be separated by an ``x'' to indicate a product. 290.Pp 291When finished, 292.Nm 293displays the number of complete and partial input and output blocks, 294truncated input records and odd-length byte-swapping blocks to the 295standard error output. 296A partial input block is one where less than the input block size 297was read. 298A partial output block is one where less than the output block size 299was written. 300Partial output blocks to tape devices are considered fatal errors. 301Otherwise, the rest of the block will be written. 302Partial output blocks to character devices will produce a warning message. 303A truncated input block is one where a variable length record oriented 304conversion value was specified and the input line was too long to 305fit in the conversion record or was not newline terminated. 306.Pp 307Normally, data resulting from input or conversion or both are aggregated 308into output blocks of the specified size. 309After the end of input is reached, any remaining output is written as 310a block. 311This means that the final output block may be shorter than the output 312block size. 313.Pp 314If 315.Nm 316receives a 317.Dv SIGINFO 318(see the ``status'' argument for 319.Xr stty 1 ) 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. 323If 324.Nm 325receives a 326.Dv SIGINT 327signal, the current input and output block counts will 328be written to the standard error output 329in the same format as the standard completion message and 330.Nm 331will exit. 332.Pp 333The 334.Nm 335utility exits 0 on success or >0 if an error occurred. 336.Sh SEE ALSO 337.Xr cp 1 , 338.Xr mt 1 , 339.Xr tr 1 340.Sh STANDARDS 341The 342.Nm 343utility is expected to be a superset of the 344.St -p1003.2 345standard. 346The 347.Cm files 348operand and the 349.Cm ascii , 350.Cm ebcdic , 351.Cm ibm , 352.Cm oldascii , 353.Cm oldebcdic 354and 355.Cm oldibm 356values are extensions to the 357.Tn POSIX 358standard. 359