DD(1) DD(1)
NAME
dd - convert and copy a file
SYNOPSIS
dd [ option value ] ...
DESCRIPTION
Dd copies the specified input file to the specified output
with possible conversions. The standard input and output
are used by default. The input and output block size may be
specified to take advantage of raw physical I/O. The
options are
-if f Open file f for input.
-of f Open file f for output.
-ibs n Set input block size to n bytes (default 512).
-obs n Set output block size (default 512).
-bs n Set both input and output block size, superseding
ibs and obs. If no conversion is specified, pre-
serve the input block size instead of packing
short blocks into the output buffer. This is
particularly efficient since no in-core copy need
be done.
-cbs n Set conversion buffer size.
-skip n Skip n input blocks before copying.
-iseek n Seek n blocks forward on input file before copy-
ing.
-iseekb n Seek n bytes forward on input file before copy-
ing.
-files n Catenate n input files (useful only for magnetic
tape or similar input device).
-oseek n Seek n blocks from beginning of output file
before copying.
-oseekb n Seek n bytes from beginning of output file before
copying.
-count n Copy only n input blocks.
-trunc n If n is 0, open the output file without truncat-
ing it.
-quiet n If n is 1, omit the summary of blocks trans-
ferred.
-conv ascii Convert EBCDIC to ASCII.
ebcdic Convert ASCII to EBCDIC.
ibm Like ebcdic but with a slightly different
character map.
block Convert variable-length ASCII records (lines)
to fixed length blocks.
unblock Convert fixed length ASCII blocks to
variable-length lines.
lcase Map alphabetics to lower case.
ucase Map alphabetics to upper case.
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DD(1) DD(1)
swab Swap every pair of bytes.
noerror Do not stop processing on an error.
sync Pad every input block to ibs bytes.
Where sizes are specified, a number of bytes is expected. A
number may end with `k' or `b' to specify multiplication by
1024 or 512 respectively; a pair of numbers may be separated
by `x' to indicate a product. Multiple conversions may be
specified in the style: `-conv ebcdic,ucase'.
`Cbs' is used only if `ascii', `unblock', `ebcdic', `ibm',
or `block' conversion is specified. In the first two cases,
n characters are copied into the conversion buffer, any
specified character mapping is done, trailing blanks are
trimmed and new-line is added before sending the line to the
output. In the latter three cases, characters are read into
the conversion buffer and blanks are added to make up an
output block of size n. If `cbs' is unspecified or zero, the
`ascii', `ebcdic', and `ibm' options convert the character
set without changing the block structure of the input file;
the `unblock' and `block' options become a simple file copy.
SOURCE
/sys/src/cmd/dd.c
SEE ALSO
cp(1)
DIAGNOSTICS
Dd reports the number of full + partial input and output
blocks handled.
Page 2 Plan 9 (printed 11/18/24)