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.\" $FreeBSD$ 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 46.Op Ar 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 ".Cm of Ns = Ns Ar file" 61.It Cm bs Ns = Ns Ar n 62Set both input and output block size to 63.Ar 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 = Ns Ar n 77Set the conversion record size to 78.Ar n 79bytes. 80The conversion record size is required by the record oriented conversion 81values. 82.It Cm count Ns = Ns Ar n 83Copy only 84.Ar n 85input blocks. 86.It Cm files Ns = Ns Ar n 87Copy 88.Ar n 89input files before terminating. 90This operand is only applicable when the input device is a tape. 91.It Cm ibs Ns = Ns Ar n 92Set the input block size to 93.Ar n 94bytes instead of the default 512. 95.It Cm if Ns = Ns Ar file 96Read input from 97.Ar file 98instead of the standard input. 99.It Cm iseek Ns = Ns Ar n 100Seek on the input file 101.Ar n 102blocks. 103This is synonymous with 104.Cm skip Ns = Ns Ar n . 105.It Cm obs Ns = Ns Ar n 106Set the output block size to 107.Ar n 108bytes instead of the default 512. 109.It Cm of Ns = Ns Ar file 110Write output to 111.Ar file 112instead of the standard output. 113Any regular output file is truncated unless the 114.Cm notrunc 115conversion value is specified. 116If an initial portion of the output file is seeked past (see the 117.Cm oseek 118operand), 119the output file is truncated at that point. 120.It Cm oseek Ns = Ns Ar n 121Seek on the output file 122.Ar n 123blocks. 124This is synonymous with 125.Cm seek Ns = Ns Ar n . 126.It Cm seek Ns = Ns Ar n 127Seek 128.Ar n 129blocks from the beginning of the output before copying. 130On non-tape devices, an 131.Xr lseek 2 132operation is used. 133Otherwise, existing blocks are read and the data discarded. 134If the user does not have read permission for the tape, it is positioned 135using the tape 136.Xr ioctl 2 137function calls. 138If the seek operation is past the end of file, space from the current 139end of file to the specified offset is filled with blocks of 140.Dv NUL 141bytes. 142.It Cm skip Ns = Ns Ar n 143Skip 144.Ar n 145blocks from the beginning of the input before copying. 146On input which supports seeks, an 147.Xr lseek 2 148operation is used. 149Otherwise, input data is read and discarded. 150For pipes, the correct number of bytes is read. 151For all other devices, the correct number of blocks is read without 152distinguishing between a partial or complete block being read. 153.It Cm conv Ns = Ns Ar value Ns Op , Ns Ar value ... 154Where 155.Cm value 156is one of the symbols from the following list. 157.Bl -tag -width ".Cm unblock" 158.It Cm ascii , oldascii 159The same as the 160.Cm unblock 161value except that characters are translated from 162.Tn EBCDIC 163to 164.Tn ASCII 165before the 166records are converted. 167(These values imply 168.Cm unblock 169if the operand 170.Cm cbs 171is also specified.) 172There are two conversion maps for 173.Tn ASCII . 174The value 175.Cm ascii 176specifies the recommended one which is compatible with 177.At V . 178The value 179.Cm oldascii 180specifies the one used in historic 181.At 182and 183.No pre- Ns Bx 4.3 reno 184systems. 185.It Cm block 186Treats the input as a sequence of newline or end-of-file terminated variable 187length records independent of input and output block boundaries. 188Any trailing newline character is discarded. 189Each input record is converted to a fixed length output record where the 190length is specified by the 191.Cm cbs 192operand. 193Input records shorter than the conversion record size are padded with spaces. 194Input records longer than the conversion record size are truncated. 195The number of truncated input records, if any, are reported to the standard 196error output at the completion of the copy. 197.It Cm ebcdic , ibm , oldebcdic , oldibm 198The same as the 199.Cm block 200value except that characters are translated from 201.Tn ASCII 202to 203.Tn EBCDIC 204after the 205records are converted. 206(These values imply 207.Cm block 208if the operand 209.Cm cbs 210is also specified.) 211There are four conversion maps for 212.Tn EBCDIC . 213The value 214.Cm ebcdic 215specifies the recommended one which is compatible with 216.At V . 217The value 218.Cm ibm 219is a slightly different mapping, which is compatible with the 220.At V 221.Cm ibm 222value. 223The values 224.Cm oldebcdic 225and 226.Cm oldibm 227are maps used in historic 228.At 229and 230.No pre- Ns Bx 4.3 reno 231systems. 232.It Cm lcase 233Transform uppercase characters into lowercase characters. 234.It Cm pareven , parnone , parodd , parset 235Output data with the specified parity. 236The parity bit on input is stripped unless 237.Tn EBCDIC 238to 239.Tn ASCII 240conversions is also specified. 241.It Cm noerror 242Do not stop processing on an input error. 243When an input error occurs, a diagnostic message followed by the current 244input and output block counts will be written to the standard error output 245in the same format as the standard completion message. 246If the 247.Cm sync 248conversion is also specified, any missing input data will be replaced 249with 250.Dv NUL 251bytes (or with spaces if a block oriented conversion value was 252specified) and processed as a normal input buffer. 253If the 254.Cm sync 255conversion is not specified, the input block is omitted from the output. 256On input files which are not tapes or pipes, the file offset 257will be positioned past the block in which the error occurred using 258.Xr lseek 2 . 259.It Cm notrunc 260Do not truncate the output file. 261This will preserve any blocks in the output file not explicitly written 262by 263.Nm . 264The 265.Cm notrunc 266value is not supported for tapes. 267.It Cm osync 268Pad the final output block to the full output block size. 269If the input file is not a multiple of the output block size 270after conversion, this conversion forces the final output block 271to be the same size as preceding blocks for use on devices that require 272regularly sized blocks to be written. 273This option is incompatible with use of the 274.Cm bs Ns = Ns Ar n 275block size specification. 276.It Cm sparse 277If one or more output blocks would consist solely of 278.Dv NUL 279bytes, try to seek the output file by the required space instead of 280filling them with 281.Dv NUL Ns s , 282resulting in a sparse file. 283.It Cm swab 284Swap every pair of input bytes. 285If an input buffer has an odd number of bytes, the last byte will be 286ignored during swapping. 287.It Cm sync 288Pad every input block to the input buffer size. 289Spaces are used for pad bytes if a block oriented conversion value is 290specified, otherwise 291.Dv NUL 292bytes are used. 293.It Cm ucase 294Transform lowercase characters into uppercase characters. 295.It Cm unblock 296Treats the input as a sequence of fixed length records independent of input 297and output block boundaries. 298The length of the input records is specified by the 299.Cm cbs 300operand. 301Any trailing space characters are discarded and a newline character is 302appended. 303.El 304.El 305.Pp 306Where sizes are specified, a decimal, octal, or hexadecimal number of 307bytes is expected. 308If the number ends with a 309.Dq Li b , 310.Dq Li k , 311.Dq Li m , 312.Dq Li g , 313or 314.Dq Li w , 315the 316number is multiplied by 512, 1024 (1K), 1048576 (1M), 1073741824 (1G) 317or the number of bytes in an integer, respectively. 318Two or more numbers may be separated by an 319.Dq Li x 320to indicate a product. 321.Pp 322When finished, 323.Nm 324displays the number of complete and partial input and output blocks, 325truncated input records and odd-length byte-swapping blocks to the 326standard error output. 327A partial input block is one where less than the input block size 328was read. 329A partial output block is one where less than the output block size 330was written. 331Partial output blocks to tape devices are considered fatal errors. 332Otherwise, the rest of the block will be written. 333Partial output blocks to character devices will produce a warning message. 334A truncated input block is one where a variable length record oriented 335conversion value was specified and the input line was too long to 336fit in the conversion record or was not newline terminated. 337.Pp 338Normally, data resulting from input or conversion or both are aggregated 339into output blocks of the specified size. 340After the end of input is reached, any remaining output is written as 341a block. 342This means that the final output block may be shorter than the output 343block size. 344.Pp 345If 346.Nm 347receives a 348.Dv SIGINFO 349(see the 350.Cm status 351argument for 352.Xr stty 1 ) 353signal, the current input and output block counts will 354be written to the standard error output 355in the same format as the standard completion message. 356If 357.Nm 358receives a 359.Dv SIGINT 360signal, the current input and output block counts will 361be written to the standard error output 362in the same format as the standard completion message and 363.Nm 364will exit. 365.Sh EXAMPLES 366Check that a disk drive contains no bad blocks: 367.Dl dd if=/dev/ad0 of=/dev/null bs=1m 368.Pp 369Do a refresh of a disk drive, in order to prevent presently 370recoverable read errors from progressing into unrecoverable read errors: 371.Dl dd if=/dev/ad0 of=/dev/ad0 bs=1m 372.Pp 373Remove parity bit from a file 374.Dl dd if=file conv=parnone of=file.txt 375.Pp 376Check for (even) parity errors on a file: 377.Dl dd if=file conv=pareven | cmp -x - file 378.Sh DIAGNOSTICS 379.Ex -std 380.Sh SEE ALSO 381.Xr cp 1 , 382.Xr mt 1 , 383.Xr tr 1 384.Sh STANDARDS 385The 386.Nm 387utility is expected to be a superset of the 388.St -p1003.2 389standard. 390The 391.Cm files 392operand and the 393.Cm ascii , 394.Cm ebcdic , 395.Cm ibm , 396.Cm oldascii , 397.Cm oldebcdic 398and 399.Cm oldibm 400values are extensions to the 401.Tn POSIX 402standard. 403