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.\" 37.Dd January 13, 1994 38.Dt DD 1 39.Os 40.Sh NAME 41.Nm dd 42.Nd convert and copy a file 43.Sh SYNOPSIS 44.Nm dd 45.Op operands ... 46.Sh DESCRIPTION 47The 48.Nm 49utility copies the standard input to the standard output. 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 dd 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 bs= Ns Ar n 61Set both input and output block size, 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 Ar n 74Set the conversion record size to 75.Va n 76bytes. 77The conversion record size is required by the record oriented conversion 78values. 79.It Cm count= Ns Ar n 80Copy only 81.Va n 82input blocks. 83.It Cm files= Ns Ar n 84Copy 85.Va n 86input files before terminating. 87This operand is only applicable when the input device is a tape. 88.It Cm ibs= Ns Ar n 89Set the input block size to 90.Va n 91bytes instead of the default 512. 92.It Cm if= Ns Ar file 93Read input from 94.Ar file 95instead of the standard input. 96.It Cm obs= Ns Ar n 97Set the output block size to 98.Va n 99bytes instead of the default 512. 100.It Cm of= Ns Ar file 101Write output to 102.Ar file 103instead of the standard output. 104Any regular output file is truncated unless the 105.Cm notrunc 106conversion value is specified. 107If an initial portion of the output file is skipped (see the 108.Cm seek 109operand) 110the output file is truncated at that point. 111.It Cm seek= Ns Ar n 112Seek 113.Va n 114blocks from the beginning of the output before copying. 115On non-tape devices, a 116.Xr lseek 2 117operation is used. 118Otherwise, existing blocks are read and the data discarded. 119If the user does not have read permission for the tape, it is positioned 120using the tape 121.Xr ioctl 2 122function calls. 123If the seek operation is past the end of file, space from the current 124end of file to the specified offset is filled with blocks of 125.Tn NUL 126bytes. 127.It Cm skip= Ns Ar n 128Skip 129.Va n 130blocks from the beginning of the input before copying. 131On input which supports seeks, a 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.Cm conv= 140.Ns Cm value Ns Op \&, Cm value \&... 141.Xc 142Where 143.Cm value 144is one of the symbols from the following list. 145.Bl -tag -width unblock 146.It Cm ascii , oldascii 147The same as the 148.Cm unblock 149value except that characters are translated from 150.Tn ECBDIC 151to 152.Tn ASCII 153before the 154records are converted. 155(These values imply 156.Cm unblock 157if the operand 158.Cm cbs 159is also specified.) 160There are two conversion maps for 161.Tn ASCII . 162The value 163.Cm ascii 164specifies the recommended one which is compatible with System V. 165The value 166.Cm oldascii 167specifies the one used in historic 168.Tn AT&T 169and pre-4.3BSD-reno systems. 170.It Cm block 171Treats the input as a sequence of newline or end-of-file terminated variable 172length records independent of input and output block boundaries. 173Any trailing newline character is discarded. 174Each input record is converted to a fixed length output record where the 175length is specified by the 176.Cm cbs 177operand. 178Input records shorter than the conversion record size are padded with spaces. 179Input records longer than the conversion record size are truncated. 180The number of truncated input records, if any, are reported to the standard 181error output at the completion of the copy. 182.It Cm ebcdic , ibm , oldebcdic , oldibm 183The same as the 184.Cm block 185value except that characters are translated from 186.Tn ASCII 187to 188.Tn EBCDIC 189after the 190records are converted. 191(These values imply 192.Cm block 193if the operand 194.Cm cbs 195is also specified.) 196There are four conversion maps for 197.Tn EBCDIC . 198The value 199.Cm ebcdic 200specifies the recommended one which is compatible with 201.At V . 202The value 203.Cm ibm 204is a slightly different mapping, which is compatible with the 205.At V 206.Cm ibm 207value. 208The values 209.Cm oldebcdic 210and 211.Cm oldibm 212are maps used in historic 213.Tn AT&T 214and pre-4.3BSD-reno systems. 215.It Cm lcase 216Transform uppercase characters into lowercase characters. 217.It Cm noerror 218Do not stop processing on an input error. 219When an input error occurs, a diagnostic message followed by the current 220input and output block counts will be written to the standard error output 221in the same format as the standard completion message. 222If the 223.Cm sync 224conversion is also specified, any missing input data will be replaced 225with 226.Tn NUL 227bytes (or with spaces if a block oriented conversion value was 228specified) and processed as a normal input buffer. 229If the 230.Cm sync 231conversion is not specified, the input block is omitted from the output. 232On input files which are not tapes or pipes, the file offset 233will be positioned past the block in which the error occurred using 234.Xr lseek 2 . 235.It Cm notrunc 236Do not truncate the output file. 237This will preserve any blocks in the output file not explicitly written 238by 239.Nm dd . 240The 241.Cm notrunc 242value is not supported for tapes. 243.It Cm osync 244Pad the final output block to the full output block size. 245If the input file is not a multiple of the output block size 246after conversion, this conversion forces the final output block 247to be the same size as preceding blocks for use on devices that require 248regularly sized blocks to be written. 249This option is incompatible with use of the 250.Cm bs= Ns Ar n 251block size specification. 252.It Cm swab 253Swap every pair of input bytes. 254If an input buffer has an odd number of bytes, the last byte will be 255ignored during swapping. 256.It Cm sync 257Pad every input block to the input buffer size. 258Spaces are used for pad bytes if a block oriented conversion value is 259specified, otherwise 260.Tn NUL 261bytes are used. 262.It Cm ucase 263Transform lowercase characters into uppercase characters. 264.It Cm unblock 265Treats the input as a sequence of fixed length records independent of input 266and output block boundaries. 267The length of the input records is specified by the 268.Cm cbs 269operand. 270Any trailing space characters are discarded and a newline character is 271appended. 272.El 273.El 274.Pp 275Where sizes are specified, a decimal number of bytes is expected. 276If the number ends with a ``b'', ``k'', ``m'' or ``w'', the number 277is multiplied by 512, 1024 (1K), 1048576 (1M) or the number of bytes 278in an integer, respectively. 279Two or more numbers may be separated by an ``x'' to indicate a product. 280.Pp 281When finished, 282.Nm dd 283displays the number of complete and partial input and output blocks, 284truncated input records and odd-length byte-swapping blocks to the 285standard error output. 286A partial input block is one where less than the input block size 287was read. 288A partial output block is one where less than the output block size 289was written. 290Partial output blocks to tape devices are considered fatal errors. 291Otherwise, the rest of the block will be written. 292Partial output blocks to character devices will produce a warning message. 293A truncated input block is one where a variable length record oriented 294conversion value was specified and the input line was too long to 295fit in the conversion record or was not newline terminated. 296.Pp 297Normally, data resulting from input or conversion or both are aggregated 298into output blocks of the specified size. 299After the end of input is reached, any remaining output is written as 300a block. 301This means that the final output block may be shorter than the output 302block size. 303.Pp 304If 305.Nm dd 306receives a 307.Dv SIGINFO 308(see the ``status'' argument for 309.Xr stty 1 ) 310signal, the current input and output block counts will 311be written to the standard error output 312in the same format as the standard completion message. 313If 314.Nm dd 315receives a 316.Dv SIGINT 317signal, the current input and output block counts will 318be written to the standard error output 319in the same format as the standard completion message and 320.Nm dd 321will exit. 322.Pp 323The 324.Nm dd 325utility exits 0 on success and >0 if an error occurred. 326.Sh SEE ALSO 327.Xr cp 1 , 328.Xr mt 1 , 329.Xr tr 1 330.Sh STANDARDS 331The 332.Nm dd 333utility is expected to be a superset of the 334.St -p1003.2 335standard. 336The 337.Cm files 338operand and the 339.Cm ascii , 340.Cm ebcdic , 341.Cm ibm , 342.Cm oldascii , 343.Cm oldebcdic 344and 345.Cm oldibm 346values are extensions to the 347.Tn POSIX 348standard. 349