DD(1)DD(1)NAMEdd - convert and copy a file
SYNOPSISdd [ option value ] ...
Dd copies the specified input file to the specified output with possi‐
ble 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 input blocks before copying.
Seek n blocks forward on input file before copying.
Seek n bytes forward on input file before copying.
Catenate n input files (useful only for magnetic tape or similar
Seek n blocks from beginning of output file before copying.
Seek n bytes from beginning of output file before copying.
Copy only n input blocks.
If n is 0, open the output file without truncating it.
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
unblock Convert fixed length ASCII blocks 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 block to ibs bytes.
Where sizes are specified, a number of bytes is expected. A number may
end with or to specify multiplication by 1024 or 512 respectively; a
pair of numbers may be separated by to indicate a product. Multiple
conversions may be specified in the style:
is used only if or conversion is specified. In the first two cases, n
characters are copied into the conversion buffer, any specified charac‐
ter 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 is unspecified or zero, the and
options convert the character set without changing the block structure
of the input file; the and options become a simple file copy.
Dd reports the number of full + partial input and output blocks han‐