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, preserve
the input block size instead of packing short blocks
into the output buffer. This is particularly effi-
cient since no in-core copy need be done.
-cbs n Set conversion buffer size.
-skip n Skip n input records before copying.
-iseek n
Seek n records forward on input file before copying.
-files n
Catenate n input files (useful only for magnetic
tape or similar input device).
-oseek n
Seek n records from beginning of output file before
copying.
-count n
Copy only n input records.
-trunc n
By default, dd truncates the output file when it
opens it; -trunc 0 opens it without truncation.
-quiet n
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DD(1) DD(1)
By default, dd prints the number of blocks read and
written once it is finished. -quiet 1 silences this
summary.
-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 to fixed
length.
unblock Convert fixed length ASCII records to variable
length.
lcase Map alphabetics to lower case.
ucase Map alphabetics to upper case.
swab Swap every pair of bytes.
noerror Do not stop processing on an error.
sync Pad every input record to ibs bytes.
Where sizes are specified, a number of bytes is expected. A
number may end with a sequence of `k', `m', `g', `t', `e',
`z', `y' to specify multiplication by 1KiB, 1MiB, etc., or
`b' to specify multiplication by 512; a pair of numbers may
be separated by `x' to indicate a product. Multiple conver-
sions 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 record of size n. If `cbs' is unspecified or zero,
the `ascii', `ebcdic', and `ibm' options convert the charac-
ter 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.
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