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5 .\" Keith Muller of the University of California, San Diego.
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35 .\" @(#)dd.1 8.2 (Berkeley) 1/13/94
36 .\" $FreeBSD: src/bin/dd/dd.1,v 1.15.2.5 2003/01/24 02:17:12 keramida Exp $
43 .Nd convert and copy a file
50 utility copies the standard input to the standard output.
51 Input data is read and written in 512-byte blocks.
52 If input reads are short, input from multiple reads are aggregated
53 to form the output block.
56 displays the number of complete and partial input and output blocks
57 and truncated input records to the standard error output.
59 The following operands are available:
60 .Bl -tag -width ".Cm of Ns = Ns Ar file"
61 .It Cm bs Ns = Ns Ar n
62 Set both input and output block size to
64 bytes, superseding the
69 If no conversion values other than
74 are specified, then each input block is copied to the output as a
75 single block without any aggregation of short blocks.
76 .It Cm cbs Ns = Ns Ar n
77 Set the conversion record size to
80 The conversion record size is required by the record oriented conversion
82 .It Cm count Ns = Ns Ar n
86 .It Cm files Ns = Ns Ar n
89 input files before terminating.
90 This operand is only applicable when the input device is a tape.
91 .It Cm ibs Ns = Ns Ar n
92 Set the input block size to
94 bytes instead of the default 512.
95 .It Cm if Ns = Ns Ar file
98 instead of the standard input.
99 .It Cm iseek Ns = Ns Ar n
100 Seek on the input file
103 This is synonymous with
104 .Cm skip Ns = Ns Ar n .
105 .It Cm obs Ns = Ns Ar n
106 Set the output block size to
108 bytes instead of the default 512.
109 .It Cm of Ns = Ns Ar file
112 instead of the standard output.
113 Any regular output file is truncated unless the
115 conversion value is specified.
116 If an initial portion of the output file is seeked past (see the
119 the output file is truncated at that point.
120 .It Cm oseek Ns = Ns Ar n
121 Seek on the output file
124 This is synonymous with
125 .Cm seek Ns = Ns Ar n .
126 .It Cm seek Ns = Ns Ar n
129 blocks from the beginning of the output before copying.
130 On non-tape devices, an
133 Otherwise, existing blocks are read and the data discarded.
134 If the user does not have read permission for the tape, it is positioned
138 If the seek operation is past the end of file, space from the current
139 end of file to the specified offset is filled with blocks of
142 .It Cm skip Ns = Ns Ar n
145 blocks from the beginning of the input before copying.
146 On input which supports seeks, an
149 Otherwise, input data is read and discarded.
150 For pipes, the correct number of bytes is read.
151 For all other devices, the correct number of blocks is read without
152 distinguishing between a partial or complete block being read.
153 .It Cm conv Ns = Ns Ar value Ns Op , Ns Ar value ...
156 is one of the symbols from the following list.
157 .Bl -tag -width ".Cm unblock"
158 .It Cm ascii , oldascii
161 value except that characters are translated from
166 records are converted.
172 There are two conversion maps for
176 specifies the recommended one which is compatible with
180 specifies the one used in historic
183 .No pre- Ns Bx 4.3 reno
186 Treats the input as a sequence of newline or end-of-file terminated variable
187 length records independent of input and output block boundaries.
188 Any trailing newline character is discarded.
189 Each input record is converted to a fixed length output record where the
190 length is specified by the
193 Input records shorter than the conversion record size are padded with spaces.
194 Input records longer than the conversion record size are truncated.
195 The number of truncated input records, if any, are reported to the standard
196 error output at the completion of the copy.
197 .It Cm ebcdic , ibm , oldebcdic , oldibm
200 value except that characters are translated from
205 records are converted.
211 There are four conversion maps for
215 specifies the recommended one which is compatible with
219 is a slightly different mapping, which is compatible with the
227 are maps used in historic
230 .No pre- Ns Bx 4.3 reno
233 Transform uppercase characters into lowercase characters.
235 Do not stop processing on an input error.
236 When an input error occurs, a diagnostic message followed by the current
237 input and output block counts will be written to the standard error output
238 in the same format as the standard completion message.
241 conversion is also specified, any missing input data will be replaced
244 bytes (or with spaces if a block oriented conversion value was
245 specified) and processed as a normal input buffer.
248 conversion is not specified, the input block is omitted from the output.
249 On input files which are not tapes or pipes, the file offset
250 will be positioned past the block in which the error occurred using
253 Do not truncate the output file.
254 This will preserve any blocks in the output file not explicitly written
259 value is not supported for tapes.
261 Pad the final output block to the full output block size.
262 If the input file is not a multiple of the output block size
263 after conversion, this conversion forces the final output block
264 to be the same size as preceding blocks for use on devices that require
265 regularly sized blocks to be written.
266 This option is incompatible with use of the
268 block size specification.
270 If one or more output blocks would consist solely of
272 bytes, try to seek the output file by the required space instead of
275 resulting in a sparse file.
277 Swap every pair of input bytes.
278 If an input buffer has an odd number of bytes, the last byte will be
279 ignored during swapping.
281 Pad every input block to the input buffer size.
282 Spaces are used for pad bytes if a block oriented conversion value is
287 Transform lowercase characters into uppercase characters.
289 Treats the input as a sequence of fixed length records independent of input
290 and output block boundaries.
291 The length of the input records is specified by the
294 Any trailing space characters are discarded and a newline character is
299 Where sizes are specified, a decimal, octal, or hexadecimal number of
301 If the number ends with a
309 number is multiplied by 512, 1024 (1K), 1048576 (1M), 1073741824 (1G)
310 or the number of bytes in an integer, respectively.
311 Two or more numbers may be separated by an
313 to indicate a product.
317 displays the number of complete and partial input and output blocks,
318 truncated input records and odd-length byte-swapping blocks to the
319 standard error output.
320 A partial input block is one where less than the input block size
322 A partial output block is one where less than the output block size
324 Partial output blocks to tape devices are considered fatal errors.
325 Otherwise, the rest of the block will be written.
326 Partial output blocks to character devices will produce a warning message.
327 A truncated input block is one where a variable length record oriented
328 conversion value was specified and the input line was too long to
329 fit in the conversion record or was not newline terminated.
331 Normally, data resulting from input or conversion or both are aggregated
332 into output blocks of the specified size.
333 After the end of input is reached, any remaining output is written as
335 This means that the final output block may be shorter than the output
346 signal, the current input and output block counts will
347 be written to the standard error output
348 in the same format as the standard completion message.
353 signal, the current input and output block counts will
354 be written to the standard error output
355 in the same format as the standard completion message and
367 utility is expected to be a superset of the
380 values are extensions to the