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. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)dd.1 8.2 (Berkeley) 1/13/94 32.\" $FreeBSD: src/bin/dd/dd.1,v 1.15.2.5 2003/01/24 02:17:12 keramida Exp $ 33.\" $DragonFly: src/bin/dd/dd.1,v 1.3 2008/01/28 16:08:02 matthias Exp $ 34.\" 35.Dd January 28, 2008 36.Dt DD 1 37.Os 38.Sh NAME 39.Nm dd 40.Nd convert and copy a file 41.Sh SYNOPSIS 42.Nm 43.Op Ar operands ... 44.Sh DESCRIPTION 45The 46.Nm 47utility copies the standard input to the standard output. 48Input data is read and written in 512-byte blocks. 49If input reads are short, input from multiple reads are aggregated 50to form the output block. 51When finished, 52.Nm 53displays the number of complete and partial input and output blocks 54and truncated input records to the standard error output. 55.Pp 56The following operands are available: 57.Bl -tag -width ".Cm of Ns = Ns Ar file" 58.It Cm bs Ns = Ns Ar n 59Set both input and output block size to 60.Ar n 61bytes, superseding the 62.Cm ibs 63and 64.Cm obs 65operands. 66If no conversion values other than 67.Cm noerror , 68.Cm notrunc 69or 70.Cm sync 71are specified, then each input block is copied to the output as a 72single block without any aggregation of short blocks. 73.It Cm cbs Ns = Ns Ar n 74Set the conversion record size to 75.Ar n 76bytes. 77The conversion record size is required by the record oriented conversion 78values. 79.It Cm count Ns = Ns Ar n 80Copy only 81.Ar n 82input blocks. 83.It Cm files Ns = Ns Ar n 84Copy 85.Ar n 86input files before terminating. 87This operand is only applicable when the input device is a tape. 88.It Cm ibs Ns = Ns Ar n 89Set the input block size to 90.Ar n 91bytes instead of the default 512. 92.It Cm if Ns = Ns Ar file 93Read input from 94.Ar file 95instead of the standard input. 96.It Cm iseek Ns = Ns Ar n 97Seek on the input file 98.Ar n 99blocks. 100This is synonymous with 101.Cm skip Ns = Ns Ar n . 102.It Cm obs Ns = Ns Ar n 103Set the output block size to 104.Ar n 105bytes instead of the default 512. 106.It Cm of Ns = Ns Ar file 107Write output to 108.Ar file 109instead of the standard output. 110Any regular output file is truncated unless the 111.Cm notrunc 112conversion value is specified. 113If an initial portion of the output file is seeked past (see the 114.Cm oseek 115operand), 116the output file is truncated at that point. 117.It Cm oseek Ns = Ns Ar n 118Seek on the output file 119.Ar n 120blocks. 121This is synonymous with 122.Cm seek Ns = Ns Ar n . 123.It Cm seek Ns = Ns Ar n 124Seek 125.Ar n 126blocks from the beginning of the output before copying. 127On non-tape devices, an 128.Xr lseek 2 129operation is used. 130Otherwise, existing blocks are read and the data discarded. 131If the user does not have read permission for the tape, it is positioned 132using the tape 133.Xr ioctl 2 134function calls. 135If the seek operation is past the end of file, space from the current 136end of file to the specified offset is filled with blocks of 137.Dv NUL 138bytes. 139.It Cm skip Ns = Ns Ar n 140Skip 141.Ar n 142blocks from the beginning of the input before copying. 143On input which supports seeks, an 144.Xr lseek 2 145operation is used. 146Otherwise, input data is read and discarded. 147For pipes, the correct number of bytes is read. 148For all other devices, the correct number of blocks is read without 149distinguishing between a partial or complete block being read. 150.It Cm conv Ns = Ns Ar value Ns Op , Ns Ar value ... 151Where 152.Cm value 153is one of the symbols from the following list. 154.Bl -tag -width ".Cm unblock" 155.It Cm ascii , oldascii 156The same as the 157.Cm unblock 158value except that characters are translated from 159.Tn EBCDIC 160to 161.Tn ASCII 162before the 163records are converted. 164(These values imply 165.Cm unblock 166if the operand 167.Cm cbs 168is also specified.) 169There are two conversion maps for 170.Tn ASCII . 171The value 172.Cm ascii 173specifies the recommended one which is compatible with 174.At V . 175The value 176.Cm oldascii 177specifies the one used in historic 178.At 179and 180.No pre- Ns Bx 4.3 reno 181systems. 182.It Cm block 183Treats the input as a sequence of newline or end-of-file terminated variable 184length records independent of input and output block boundaries. 185Any trailing newline character is discarded. 186Each input record is converted to a fixed length output record where the 187length is specified by the 188.Cm cbs 189operand. 190Input records shorter than the conversion record size are padded with spaces. 191Input records longer than the conversion record size are truncated. 192The number of truncated input records, if any, are reported to the standard 193error output at the completion of the copy. 194.It Cm ebcdic , ibm , oldebcdic , oldibm 195The same as the 196.Cm block 197value except that characters are translated from 198.Tn ASCII 199to 200.Tn EBCDIC 201after the 202records are converted. 203(These values imply 204.Cm block 205if the operand 206.Cm cbs 207is also specified.) 208There are four conversion maps for 209.Tn EBCDIC . 210The value 211.Cm ebcdic 212specifies the recommended one which is compatible with 213.At V . 214The value 215.Cm ibm 216is a slightly different mapping, which is compatible with the 217.At V 218.Cm ibm 219value. 220The values 221.Cm oldebcdic 222and 223.Cm oldibm 224are maps used in historic 225.At 226and 227.No pre- Ns Bx 4.3 reno 228systems. 229.It Cm lcase 230Transform uppercase characters into lowercase characters. 231.It Cm noerror 232Do not stop processing on an input error. 233When an input error occurs, a diagnostic message followed by the current 234input and output block counts will be written to the standard error output 235in the same format as the standard completion message. 236If the 237.Cm sync 238conversion is also specified, any missing input data will be replaced 239with 240.Dv NUL 241bytes (or with spaces if a block oriented conversion value was 242specified) and processed as a normal input buffer. 243If the 244.Cm sync 245conversion is not specified, the input block is omitted from the output. 246On input files which are not tapes or pipes, the file offset 247will be positioned past the block in which the error occurred using 248.Xr lseek 2 . 249.It Cm notrunc 250Do not truncate the output file. 251This will preserve any blocks in the output file not explicitly written 252by 253.Nm . 254The 255.Cm notrunc 256value is not supported for tapes. 257.It Cm osync 258Pad the final output block to the full output block size. 259If the input file is not a multiple of the output block size 260after conversion, this conversion forces the final output block 261to be the same size as preceding blocks for use on devices that require 262regularly sized blocks to be written. 263This option is incompatible with use of the 264.Cm bs Ns = Ns Ar n 265block size specification. 266.It Cm sparse 267If one or more output blocks would consist solely of 268.Dv NUL 269bytes, try to seek the output file by the required space instead of 270filling them with 271.Dv NUL Ns s , 272resulting in a sparse file. 273.It Cm swab 274Swap every pair of input bytes. 275If an input buffer has an odd number of bytes, the last byte will be 276ignored during swapping. 277.It Cm sync 278Pad every input block to the input buffer size. 279Spaces are used for pad bytes if a block oriented conversion value is 280specified, otherwise 281.Dv NUL 282bytes are used. 283.It Cm ucase 284Transform lowercase characters into uppercase characters. 285.It Cm unblock 286Treats the input as a sequence of fixed length records independent of input 287and output block boundaries. 288The length of the input records is specified by the 289.Cm cbs 290operand. 291Any trailing space characters are discarded and a newline character is 292appended. 293.El 294.El 295.Pp 296Where sizes are specified, a decimal, octal, or hexadecimal number of 297bytes is expected. 298If the number ends with a 299.Dq Li b , 300.Dq Li B , 301.Dq Li k , 302.Dq Li K , 303.Dq Li m , 304.Dq Li M , 305.Dq Li g , 306.Dq Li G , 307or 308.Dq Li w , 309the 310number is multiplied by 512, 1024 (1K), 1048576 (1M), 1073741824 (1G) 311or the number of bytes in an integer, respectively. 312Two or more numbers may be separated by an 313.Dq Li x 314to indicate a product. 315.Pp 316When finished, 317.Nm 318displays the number of complete and partial input and output blocks, 319truncated input records and odd-length byte-swapping blocks to the 320standard error output. 321A partial input block is one where less than the input block size 322was read. 323A partial output block is one where less than the output block size 324was written. 325Partial output blocks to tape devices are considered fatal errors. 326Otherwise, the rest of the block will be written. 327Partial output blocks to character devices will produce a warning message. 328A truncated input block is one where a variable length record oriented 329conversion value was specified and the input line was too long to 330fit in the conversion record or was not newline terminated. 331.Pp 332Normally, data resulting from input or conversion or both are aggregated 333into output blocks of the specified size. 334After the end of input is reached, any remaining output is written as 335a block. 336This means that the final output block may be shorter than the output 337block size. 338.Pp 339If 340.Nm 341receives a 342.Dv SIGINFO 343(see the 344.Cm status 345argument for 346.Xr stty 1 ) 347signal, the current input and output block counts will 348be written to the standard error output 349in the same format as the standard completion message. 350If 351.Nm 352receives a 353.Dv SIGINT 354signal, the current input and output block counts will 355be written to the standard error output 356in the same format as the standard completion message and 357.Nm 358will exit. 359.Sh EXIT STATUS 360.Ex -std 361.Sh SEE ALSO 362.Xr cp 1 , 363.Xr mt 1 , 364.Xr tr 1 365.Sh STANDARDS 366The 367.Nm 368utility is expected to be a superset of the 369.St -p1003.2 370standard. 371The 372.Cm files 373operand and the 374.Cm ascii , 375.Cm ebcdic , 376.Cm ibm , 377.Cm oldascii , 378.Cm oldebcdic 379and 380.Cm oldibm 381values are extensions to the 382.Tn POSIX 383standard. 384