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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 efficient since no in-core copy need be done.
−cbs n Set conversion buffer size.
−skip n Skip n input records before copying.
−iseek nSeek n records forward on input file before copying.
−files nCatenate n input files (useful only for magnetic tape
or similar input device).
−oseek nSeek n records from beginning of output file before copying.
−count nCopy only n input records.
−trunc nBy default, dd truncates the output file when it opens
it; −trunc 0 opens it without truncation.
−quiet nBy 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.
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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.
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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 record
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.
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