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.\" $Id$ 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 dd 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, superseding the 63.Cm ibs 64and 65.Cm obs 66operands. 67If no conversion values other than 68.Cm noerror , 69.Cm notrunc 70or 71.Cm sync 72are specified, then each input block is copied to the output as a 73single block without any aggregation of short blocks. 74.It Cm cbs= Ns Ar n 75Set the conversion record size to 76.Va n 77bytes. 78The conversion record size is required by the record oriented conversion 79values. 80.It Cm count= Ns Ar n 81Copy only 82.Va n 83input blocks. 84.It Cm files= Ns Ar n 85Copy 86.Va n 87input files before terminating. 88This operand is only applicable when the input device is a tape. 89.It Cm ibs= Ns Ar n 90Set the input block size to 91.Va n 92bytes instead of the default 512. 93.It Cm if= Ns Ar file 94Read input from 95.Ar file 96instead of the standard input. 97.It Cm obs= Ns Ar n 98Set the output block size to 99.Va n 100bytes instead of the default 512. 101.It Cm of= Ns Ar file 102Write output to 103.Ar file 104instead of the standard output. 105Any regular output file is truncated unless the 106.Cm notrunc 107conversion value is specified. 108If an initial portion of the output file is skipped (see the 109.Cm seek 110operand) 111the output file is truncated at that point. 112.It Cm seek= Ns Ar n 113Seek 114.Va n 115blocks from the beginning of the output before copying. 116On non-tape devices, a 117.Xr lseek 2 118operation is used. 119Otherwise, existing blocks are read and the data discarded. 120If the user does not have read permission for the tape, it is positioned 121using the tape 122.Xr ioctl 2 123function calls. 124If the seek operation is past the end of file, space from the current 125end of file to the specified offset is filled with blocks of 126.Tn NUL 127bytes. 128.It Cm skip= Ns Ar n 129Skip 130.Va n 131blocks from the beginning of the input before copying. 132On input which supports seeks, a 133.Xr lseek 2 134operation is used. 135Otherwise, input data is read and discarded. 136For pipes, the correct number of bytes is read. 137For all other devices, the correct number of blocks is read without 138distinguishing between a partial or complete block being read. 139.It Xo 140.Cm conv= 141.Ns Cm value Ns Op \&, Cm value \&... 142.Xc 143Where 144.Cm value 145is one of the symbols from the following list. 146.Bl -tag -width unblock 147.It Cm ascii , oldascii 148The same as the 149.Cm unblock 150value except that characters are translated from 151.Tn ECBDIC 152to 153.Tn ASCII 154before the 155records are converted. 156(These values imply 157.Cm unblock 158if the operand 159.Cm cbs 160is also specified.) 161There are two conversion maps for 162.Tn ASCII . 163The value 164.Cm ascii 165specifies the recommended one which is compatible with System V. 166The value 167.Cm oldascii 168specifies the one used in historic 169.Tn AT&T 170and pre-4.3BSD-reno systems. 171.It Cm block 172Treats the input as a sequence of newline or end-of-file terminated variable 173length records independent of input and output block boundaries. 174Any trailing newline character is discarded. 175Each input record is converted to a fixed length output record where the 176length is specified by the 177.Cm cbs 178operand. 179Input records shorter than the conversion record size are padded with spaces. 180Input records longer than the conversion record size are truncated. 181The number of truncated input records, if any, are reported to the standard 182error output at the completion of the copy. 183.It Cm ebcdic , ibm , oldebcdic , oldibm 184The same as the 185.Cm block 186value except that characters are translated from 187.Tn ASCII 188to 189.Tn EBCDIC 190after the 191records are converted. 192(These values imply 193.Cm block 194if the operand 195.Cm cbs 196is also specified.) 197There are four conversion maps for 198.Tn EBCDIC . 199The value 200.Cm ebcdic 201specifies the recommended one which is compatible with 202.At V . 203The value 204.Cm ibm 205is a slightly different mapping, which is compatible with the 206.At V 207.Cm ibm 208value. 209The values 210.Cm oldebcdic 211and 212.Cm oldibm 213are maps used in historic 214.Tn AT&T 215and pre-4.3BSD-reno systems. 216.It Cm lcase 217Transform uppercase characters into lowercase characters. 218.It Cm noerror 219Do not stop processing on an input error. 220When an input error occurs, a diagnostic message followed by the current 221input and output block counts will be written to the standard error output 222in the same format as the standard completion message. 223If the 224.Cm sync 225conversion is also specified, any missing input data will be replaced 226with 227.Tn NUL 228bytes (or with spaces if a block oriented conversion value was 229specified) and processed as a normal input buffer. 230If the 231.Cm sync 232conversion is not specified, the input block is omitted from the output. 233On input files which are not tapes or pipes, the file offset 234will be positioned past the block in which the error occurred using 235.Xr lseek 2 . 236.It Cm notrunc 237Do not truncate the output file. 238This will preserve any blocks in the output file not explicitly written 239by 240.Nm dd . 241The 242.Cm notrunc 243value is not supported for tapes. 244.It Cm osync 245Pad the final output block to the full output block size. 246If the input file is not a multiple of the output block size 247after conversion, this conversion forces the final output block 248to be the same size as preceding blocks for use on devices that require 249regularly sized blocks to be written. 250This option is incompatible with use of the 251.Cm bs= Ns Ar n 252block size specification. 253.It Cm swab 254Swap every pair of input bytes. 255If an input buffer has an odd number of bytes, the last byte will be 256ignored during swapping. 257.It Cm sync 258Pad every input block to the input buffer size. 259Spaces are used for pad bytes if a block oriented conversion value is 260specified, otherwise 261.Tn NUL 262bytes are used. 263.It Cm ucase 264Transform lowercase characters into uppercase characters. 265.It Cm unblock 266Treats the input as a sequence of fixed length records independent of input 267and output block boundaries. 268The length of the input records is specified by the 269.Cm cbs 270operand. 271Any trailing space characters are discarded and a newline character is 272appended. 273.El 274.El 275.Pp 276Where sizes are specified, a decimal number of bytes is expected. 277If the number ends with a ``b'', ``k'', ``m'' or ``w'', the number 278is multiplied by 512, 1024 (1K), 1048576 (1M) or the number of bytes 279in an integer, respectively. 280Two or more numbers may be separated by an ``x'' to indicate a product. 281.Pp 282When finished, 283.Nm dd 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 dd 307receives a 308.Dv SIGINFO 309(see the ``status'' argument for 310.Xr stty 1 ) 311signal, the current input and output block counts will 312be written to the standard error output 313in the same format as the standard completion message. 314If 315.Nm dd 316receives a 317.Dv SIGINT 318signal, the current input and output block counts will 319be written to the standard error output 320in the same format as the standard completion message and 321.Nm dd 322will exit. 323.Pp 324The 325.Nm dd 326utility exits 0 on success and >0 if an error occurred. 327.Sh SEE ALSO 328.Xr cp 1 , 329.Xr mt 1 , 330.Xr tr 1 331.Sh STANDARDS 332The 333.Nm dd 334utility is expected to be a superset of the 335.St -p1003.2 336standard. 337The 338.Cm files 339operand and the 340.Cm ascii , 341.Cm ebcdic , 342.Cm ibm , 343.Cm oldascii , 344.Cm oldebcdic 345and 346.Cm oldibm 347values are extensions to the 348.Tn POSIX 349standard. 350