1.\" Copyright (c) 1990 The Regents of the University of California. 2.\" 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 6.7 (Berkeley) 8/7/91 36.\" 37.Dd August 7, 1991 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 170.Pf pre- Bx 4.3 reno 171systems. 172.It Cm block 173Treats the input as a sequence of newline or end-of-file terminated variable 174length records independent of input and output block boundaries. 175Any trailing newline character is discarded. 176Each input record is converted to a fixed length output record where the 177length is specified by the 178.Cm cbs 179operand. 180Input records shorter than the conversion record size are padded with spaces. 181Input records longer than the conversion record size are truncated. 182The number of truncated input records, if any, are reported to the standard 183error at the completion of the copy. 184.It Cm ebcdic , ibm , oldebcdic , oldibm 185The same as the 186.Cm block 187value except that characters are translated from 188.Tn ASCII 189to 190.Tn EBCDIC 191after the 192records are converted. 193(These values imply 194.Cm block 195if the operand 196.Cm cbs 197is also specified.) 198There are four conversion maps for 199.Tn EBCDIC . 200The value 201.Cm ebcdic 202specifies the recommended one which is compatible with 203.At V . 204The value 205.Cm ibm 206is a slightly different mapping, which is compatible with the 207.At V 208.Cm ibm 209value. 210The values 211.Cm oldebcdic 212and 213.Cm oldibm 214are maps used in historic 215.Tn AT&T 216and 217.Pf pre- Bx 4.3 reno 218systems. 219.It Cm lcase 220Transform uppercase characters into lowercase characters. 221.It Cm noerror 222Do not stop processing on an input error. 223When an input error occurs, a diagnostic message followed by the current 224input and output block counts will be written to standard error in the 225same format as the standard completion message. 226If the 227.Cm sync 228conversion is also specified, any missing input data will be replaced 229with 230.Tn NUL 231bytes (or with spaces if a block oriented conversion value was 232specified) and processed as a normal input buffer. 233If the 234.Cm sync 235conversion is not specified, the input block is omitted from the output. 236On input files which are not tapes or pipes, the file offset 237will be positioned past the block in which the error occurred using 238.Xr lseek 2 . 239.It Cm notrunc 240Do not truncate the output file. 241This will preserve any blocks in the output file not explicitly written 242by 243.Nm dd . 244The 245.Cm notrunc 246value is not supported for tapes. 247.It Cm swab 248Swap every pair of input bytes. 249If an input buffer has an odd number of bytes, the last byte will be 250ignored during swapping. 251.It Cm sync 252Pad every input block to the input buffer size. 253Spaces are used for pad bytes if a block oriented conversion value is 254specified, otherwise 255.Tn NUL 256bytes are used. 257.It Cm ucase 258Transform lowercase characters into uppercase characters. 259.It Cm unblock 260Treats the input as a sequence of fixed length records independent of input 261and output block boundaries. 262The length of the input records is specified by the 263.Cm cbs 264operand. 265Any trailing space characters are discarded and a newline character is 266appended. 267.El 268.El 269.Pp 270Where sizes are specified, a decimal number of bytes is expected. 271If the number ends with a ``b'', ``k'', ``m'' or ``w'', the number 272is multiplied by 512, 1024 (1K), 1048576 (1M) or the number of bytes 273in an integer, respectively. 274Two or more numbers may be separated by an ``x'' to indicate a product. 275.Pp 276When finished, 277.Nm dd 278displays the number of complete and partial input and output blocks, 279truncated input records and odd-length byte-swapping blocks to the 280standard error output. 281A partial input block is one where less than the input block size 282was read. 283A partial output block is one where less than the output block size 284was written. 285Partial output blocks to tape devices are considered fatal errors. 286Otherwise, the rest of the block will be written. 287Partial output blocks to character devices will produce a warning message. 288A truncated input block is one where a variable length record oriented 289conversion value was specified and the input line was too long to 290fit in the conversion record or was not newline terminated. 291.Pp 292Normally, data resulting from input or conversion or both are aggregated 293into output blocks of the specified size. 294After the end of input is reached, any remaining output is written as 295a block. 296This means that the final output block may be shorter than the output 297block size. 298.Pp 299If 300.Nm dd 301receives a 302.Dv SIGINFO 303(see the ``status'' argument for 304.Xr stty 1 ) 305signal, the current input and output block counts will 306be written to standard error in the same format as the standard completion 307message. 308If 309.Nm dd 310receives a 311.Dv SIGINT 312signal, the current input and output block counts will 313be written to standard error in the same format as the standard completion 314message and 315.Nm dd 316will exit. 317.Pp 318The 319.Nm dd 320utility exits 0 on success and >0 if an error occurred. 321.Sh SEE ALSO 322.Xr cp 1 , 323.Xr mt 1 , 324.Xr tr 1 325.Sh STANDARDS 326The 327.Nm dd 328utility is expected to be a superset of the 329.St -p1003.2 330standard. 331The 332.Cm files 333operand and the 334.Cm ascii , 335.Cm ebcdic , 336.Cm ibm , 337.Cm oldascii , 338.Cm oldebcdic 339and 340.Cm oldibm 341values are extensions to the 342.Tn POSIX 343standard. 344