dd – convert and copy a file

dd [ option value ] ...

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 blocks before copying.
iseek n   Seek n blocks forward on input file before copying.
iseekb nSeek n bytes 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 blocks from beginning of output file before copying.
oseekb nSeek 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 truncating it.
quiet n   If n is 1, omit the summary of blocks transferred.
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.
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.



Dd reports the number of full + partial input and output blocks handled.
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