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
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34.\"
35.\" @(#)dd.1 8.2 (Berkeley) 1/13/94
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36.\" $Id: dd.1,v 1.5 1997/04/28 04:07:29 steve Exp $
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| 36.\" $Id: dd.1,v 1.6 1997/10/11 20:09:04 joerg Exp $ |
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,
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55.Nm dd
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| 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 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 EBCDIC
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
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240.Nm dd .
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| 240.Nm Ns . |
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 sparse
254If one or more output blocks would consist solely of
255.Tn NUL
256bytes, try to seek the output file by the required space instead of
257filling them with
258.Tn NULs ,
259resulting in a sparse file.
260.It Cm swab
261Swap every pair of input bytes.
262If an input buffer has an odd number of bytes, the last byte will be
263ignored during swapping.
264.It Cm sync
265Pad every input block to the input buffer size.
266Spaces are used for pad bytes if a block oriented conversion value is
267specified, otherwise
268.Tn NUL
269bytes are used.
270.It Cm ucase
271Transform lowercase characters into uppercase characters.
272.It Cm unblock
273Treats the input as a sequence of fixed length records independent of input
274and output block boundaries.
275The length of the input records is specified by the
276.Cm cbs
277operand.
278Any trailing space characters are discarded and a newline character is
279appended.
280.El
281.El
282.Pp
283Where sizes are specified, a decimal number of bytes is expected.
284If the number ends with a ``b'', ``k'', ``m'' or ``w'', the number
285is multiplied by 512, 1024 (1K), 1048576 (1M) or the number of bytes
286in an integer, respectively.
287Two or more numbers may be separated by an ``x'' to indicate a product.
288.Pp
289When finished,
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290.Nm dd
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| 290.Nm |
291displays the number of complete and partial input and output blocks,
292truncated input records and odd-length byte-swapping blocks to the
293standard error output.
294A partial input block is one where less than the input block size
295was read.
296A partial output block is one where less than the output block size
297was written.
298Partial output blocks to tape devices are considered fatal errors.
299Otherwise, the rest of the block will be written.
300Partial output blocks to character devices will produce a warning message.
301A truncated input block is one where a variable length record oriented
302conversion value was specified and the input line was too long to
303fit in the conversion record or was not newline terminated.
304.Pp
305Normally, data resulting from input or conversion or both are aggregated
306into output blocks of the specified size.
307After the end of input is reached, any remaining output is written as
308a block.
309This means that the final output block may be shorter than the output
310block size.
311.Pp
312If
|
313.Nm dd
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| 313.Nm |
314receives a
315.Dv SIGINFO
316(see the ``status'' argument for
317.Xr stty 1 )
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.
321If
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322.Nm dd
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| 322.Nm |
323receives a
324.Dv SIGINT
325signal, the current input and output block counts will
326be written to the standard error output
327in the same format as the standard completion message and
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328.Nm dd
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| 328.Nm |
329will exit.
330.Pp
331The
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332.Nm dd
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| 332.Nm |
333utility exits 0 on success and >0 if an error occurred.
334.Sh SEE ALSO
335.Xr cp 1 ,
336.Xr mt 1 ,
337.Xr tr 1
338.Sh STANDARDS
339The
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340.Nm dd
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| 340.Nm |
341utility is expected to be a superset of the
342.St -p1003.2
343standard.
344The
345.Cm files
346operand and the
347.Cm ascii ,
348.Cm ebcdic ,
349.Cm ibm ,
350.Cm oldascii ,
351.Cm oldebcdic
352and
353.Cm oldibm
354values are extensions to the
355.Tn POSIX
356standard.
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